hep-ph — Pith

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hep-ph 2026-05-13 Recognition

Quasi PDFs converge and obey sum rules in gauge-free models

Quasi Parton Distribution Functions in Covariant Quark Models

General proofs for unpolarized quarks and antiquarks hold for both Dirac matrix choices, with analytical small-x results in the covariant

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Quasi parton distribution functions (QPDFs) are defined in terms of QCD fields at spacelike separations evaluated in matrix elements of hadrons moving with velocity $v$. These objects can be studied in lattice QCD. In the limit when $v$ approaches the speed of light, QPDFs converge to PDFs. It is insightful to study QPDFs and their convergence in models. In this work, we first study the QPDFs in a broad class of quark models characterized by one common feature, namely the absence of gauge degrees of freedom. We provide general proofs for the convergence and sum rules of the unpolarized quark and antiquark QPDFs for both choices $\gamma^0$ and $\gamma^3$. We choose the Covariant Parton Model (CPM) as an illustration. We derive analytical results for the small-$x_v$ behavior of QPDFs and the energy-momentum tensor form factor $\bar{c}^q(t)$ at zero momentum transfer. These results are of interest as they correspond to a Wandzura-Wilczek-type approximation.

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hep-ph 2026-05-13 2 theorems

Auxiliary-field lineshape fits molecular X like deuteron data

A New Look at the X Compositeness from its Lineshape

The parametrization treats X as an unphysical auxiliary field and reproduces np-deuteron scattering, offering a direct test for X(3872) as a

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The existing analyses on the X(3872) lineshape are consistent with the hypothesis that it is a compact particle composed of four quarks. This conclusion follows from fitting available data with a Flatte' distribution derived from an effective Lagrangian in which X, D, and D* are all elementary fields. A molecular X, i.e., a deuteron-like bound state of D and Dbar*, must instead be described by an effective theory where the X field is initially absent or introduced as an auxiliary, unphysical, field, yielding a lineshape parametrization that differs significantly from the Flatte' one. We demonstrate, in the analogous theory of nucleons with an auxiliary deuteron field, that this parametrization gives a fully consistent description of np--> deuteron --> np scattering data, and motivate applying the same method to the X lineshape.

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hep-ph 2026-05-13 Recognition

Reanalysis sets first bound on charge-dependent free fall

Toward Charge-Dependent Tests of the Equivalence Principle: A Phenomenological Parameter and an Unexplored Frontier

Existing tests imply |κ| < 2.1 × 10^{-4} kg/C for linear charge-gravity coupling, showing the electromagnetic axis remains largely untested.

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We introduce and define the phenomenological parameter $\kappa$, defined by $\Delta a/g = \kappa \, \Delta(q/m)$, to quantify potential linear coupling between electric charge and gravitational acceleration. A synthesis of existing precision equivalence principle experiments yields the first quantitative estimate of the effective sensitivity to this coupling: $|\kappa| < 2.1 \times 10^{-4}~\si{\kilo\gram\per\coulomb}$ at 95\% confidence level. This constraint is approximately eleven orders of magnitude less stringent than corresponding bounds on composition-dependent violations, revealing that the electromagnetic axis remains a largely underexplored frontier in empirical gravity. We connect $\kappa$ to established frameworks -- the Standard-Model Extension and the $TH\epsilon\mu$ formalism -- showing that it occupies a region of parameter space untouched by existing high-precision tests. An effective field theory analysis shows that dimension-six operators that couple curvature directly to the electromagnetic field strength are suppressed by the minuscule terrestrial spacetime curvature ($G_N \rho_\oplus \sim 10^{-55}~\text{GeV}^2$) and are therefore phenomenologically irrelevant. Consequently, a future measurement of $\kappa$ at an accessible level would not probe minimal geometric couplings but would signal physics beyond minimal gravitational EFT, such as mediation by light scalar fields as in Einstein-Maxwell-Dilaton theory. We examine the Schiff-Barnhill effect, the primary systematic background for any such measurement, and show how it can be separated from a genuine signal. We outline the necessary experimental strategy, focused on maximizing charge-to-mass ratio differences, to transform this overlooked axis into a targeted probe for new physics.

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hep-ph 2026-05-13 Recognition

Open LHC event sharing cuts duplicated simulations

Open LHC Monte Carlo Event Generation

Review details how reusable Monte Carlo data lowers effort, costs, and energy use for the physics community

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The LHC physics programme involves a vast amount of Monte Carlo event simulation. This paper reviews current efforts towards sharing the generated events as Open Data. Open Event Generation helps reduce duplication of effort and resource consumption, and benefits the whole High Energy Physics community. We give examples of use cases and user experiences, discuss financial and environmental savings, and suggest future directions.

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hep-ph 2026-05-13 1 theorem

Lattice and tau data match on hadronic vacuum polarization

Comparison of the hadronic vacuum polarization between hadronic τ-decay data and lattice QCD

Overall agreement supports muon g-2 calculations, but the 2π−π+π0 four-pion mode shows significant differences from e+e− expectations.

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We compare the isospin-one, vector-current hadronic vacuum polarization (HVP) obtained from isospin-symmetric lattice QCD with that obtained from a dispersive representation employing inclusive hadronic $\tau$ decay data corrected for isospin breaking. We consider the subtracted HVP evaluated at squared Euclidean momenta ranging from $0.5$ GeV$^2$ to $12$ GeV$^2$, together with the light-quark-connected HVP contribution to the muon anomalous magnetic moment and the short-, intermediate- and long-distance RBC/UKQCD window components thereof. Dispersive contributions from the region of hadronic invariant masses above the $\tau$ mass are evaluated using perturbative QCD. We also consider dispersive determinations using $\tau$ data only for contributions from two-pion, or two-pion and four-pion, modes, and evaluating the remaining contributions using exclusive-mode $e^+e^-\to\mbox{hadrons}$ cross sections up to about 2 GeV, lessening the dependence on perturbation theory. We find generally good agreement between lattice and $\tau$-based results. However, a comparison of $\tau$-based window-quantity contributions for the two four-pion modes to expectations for those contributions based on the Pais relations and $e^+e^-$ four-pion cross sections, reveals significant differences for the $2\pi^-\pi^+\pi^0$ mode.

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hep-ph 2026-05-13 Recognition

J/Ψ photoproduction feasible in peripheral OO collisions

Photoproduction of J/Psi in peripheral Oxygen-Oxygen collisions

Model calculations predict observable rates at the LHC; OO data combined with PbPb results can constrain photon-induced process descriptions

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The photoproduction of $J/\Psi$ in peripheral Oxygen - Oxygen ($OO$) collisions at the Large Hadron Collider (LHC) is investigated considering distinct assumptions for the modeling of the nuclear photon flux, overlap function and dipole - proton scattering amplitude. Predictions for the associated rapidity distributions and total cross - sections are presented. Our results indicate that the experimental study of the photoproduction of $J/\Psi$ in peripheral $OO$ collisions is, in principle, feasible. In addition, they point out that the combination of the results for this final state in $OO$ collisions with those obtained for $PbPb$ collisions will allow us to derive important constraints on the description of photon - induced process at peripheral collisions.

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hep-ph 2026-05-13 2 theorems

Mixing angle tunes rates of B decays to excited D mesons

A Phenomenological Study of Semileptonic B^+ and B_s⁰ Decays into Axial-Vector Mesons big(D₁(2420),\, D₁^prime(2430),\, D_{s1}(2460),\, and D_{s1}^prime(2536)big) within the Standard Model

Branching fractions, asymmetries, and polarization observables vary with the admixture of angular-momentum states, giving benchmarks to test

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We study semileptonic $B$ meson decays $B^+ \to D_1^{(\prime)}\ell^+\nu_\ell$ and $B_s^0 \to D_{s1}^{-(\prime)}\ell^+\nu_\ell$, where $\ell=\mu,\tau$. The final state axial vector mesons are treated as mixtures of the heavy quark basis states with light degree of freedom angular momenta $j_\ell=1/2$ and $j_\ell=3/2$, parametrized by the mixing angle $\theta_{D_1}$. Using form factors obtained in the covariant light front quark model, we analyze the dependence of various observables on $\theta_{D_1}$ such as polarized and unpolarized branching ratios, the lepton forward-backward asymmetry, the longitudinal polarization fraction, and the lepton flavor universality ratios. In addition, we also discuss correlations among different observables. We study these observables in the experimentally motivated mixing angle regions as well as over a wider range of $\theta_{D_1}$. Our results show that branching ratios and other observables are sensitive to the axial-vector mixing structure. These predictions provide useful Standard Model benchmarks for future measurements of semileptonic $B_{(s)}$ decays into orbitally excited mesons and may help to clarify the long standing $1/2$ vs. $3/2$ puzzle in semileptonic $B$ decays.

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hep-ph 2026-05-13 2 theorems

Tree unitarity fully fixed by amplitudes up to five points

Explicit Conditions for Diagnosing Tree-Level Unitarity

Explicit coupling conditions let physicists check consistency of spin-≤1 theories using only particle content without the full Lagrangian.

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We explicitly present all coupling conditions required for tree-level unitarity (tree unitarity) in theories with a finite number of massive and massless particles of spin up to 1. They allow us to diagnose tree unitarity of a system using only its particle content in the mass basis, without reconstructing the full Lagrangian. We show that all four-point amplitudes whose high-energy growth is canceled by tree unitarity conditions are on-shell constructible, thereby motivating the recursive construction of four-point amplitudes. By examining their high-energy growth, we derive tree unitarity conditions for four-point amplitudes. Imposing these conditions to simplify the Lagrangian structure, we use the St\"uckelberg formulation to derive the tree unitarity conditions arising from all higher-point amplitudes. We show that all tree unitarity conditions are fully captured up to five-point amplitudes, ensuring no necessity of examining higher-point ones. We apply our results to systematically examine tree unitarity conditions in the dark sector with a massive dark photon and dark matter particles of spin up to 1, and extract the essential features for mass generation in the massive dark photon case. In addition, we show that our results allow us to conclude that theories without scalars require an infinite tower of vectors and fermions for tree unitarity. Finally unitarity and related issues in the Higgs portal VDM are discussed in brief.

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hep-ph 2026-05-13 2 theorems

Top-antitop pairs at LHC carry spin quantumness that flags anomalous couplings

Quantumness of top quark pairs produced at LHC within SMEFT framework

Entanglement and discord respond differently to chromo-dipole versus weak-dipole operators near threshold within SMEFT.

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Top and anti-top quark pair production at LHC provides a unique setting to probe non-classical correlations at the TeV scale. We study quantum information (QI) properties of the $t\bar{t}$ spin state in $pp$ collisions at $\sqrt{s}=13$ TeV within the Standard Model Effective Field Theory (SMEFT), focusing on dimension-6 operators that induce anomalous chromo- and weak dipole moments of the top quark within their current experimental bounds. The $t\bar{t}$ spin density matrix is reconstructed from the joint angular distribution of the final state charged leptons in the $k$-$r$-$n$ helicity basis. We analyze three complementary QI quantities: concurrence-based quantum entanglement (QE), geometric quantum discord (GQD), and the Bell parameter,across four $t\bar{t}$ invariant-mass bins. Within the Standard Model (SM), non-vanishing QE appears only near threshold ($m_{t\bar{t}}\lesssim 400$ GeV), while GQD remains nonzero across the full phase space, indicating persistent non-classical correlations even for separable states. Anomalous chromo-dipole interactions modify these observables primarily near threshold: $\hat{\mu}_t$ induces asymmetric shifts, whereas $\hat{d}_t$ produces a mild symmetric response without Bell inequality violation. Among weak dipole operators, the CP-even coupling $C_2^V$ generates the largest deformation of the QI observables, while $\Delta C_1^{A,V}$ leave them unchanged. These results demonstrate that QI observables derived from the $t\bar{t}$ spin density matrix provide a complementary probe of anomalous top-quark interactions with distinct sensitivity to CP-even and CP-odd operator structures.

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hep-ph 2026-05-13 Recognition

Cooler relic neutrinos reveal small-scale primordial power

Probing the small-scale primordial power spectrum via relic neutrinos and acoustic reheating

Damping of early density ripples after neutrino decoupling reduces their abundance, letting PTOLEMY limit fluctuations on scales k ≲ 3×10^5

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We show that the dissipation of small-scale perturbations through diffusion damping after neutrino decoupling lowers the present-day neutrino temperature compared to the expected value of $1.96\,{\text{K}}$. This reduces the relic neutrino abundance by an amount controlled by the integral of the primordial curvature power spectrum $\Delta_{\cal R}^2(k)$. We find that a relic neutrino detection by PTOLEMY can set limits $\Delta_{\cal R}^2(k) \lesssim {\cal O}(0.1)$ on scales $k \lesssim 3 \times 10^5\,{\text{Mpc}^{-1}}$, complementary to limits from Big Bang Nucleosynthesis, spectral distortions, pulsar timing arrays, and future dark ages 21-cm observations.

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hep-ph 2026-05-13 1 theorem

T-dependent g and mu let van der Waals model match QCD thermodynamics

Trace anomaly, effective degrees of freedom, and chemical potential effects near the QCD crossover

The adjustments reproduce the trace anomaly peak near the crossover without extra terms or new sectors.

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A compact analytical scheme is presented for describing ultra-dense hadronic matter, which combines a multicomponent van der Waals (vdW)-type description with temperature-dependent effective degrees of freedom. Although the vdW formalism successfully reproduces interactions at finite density, in its standard form it cannot describe lattice-QCD thermodynamics, since it uses a fixed degeneracy. It is shown that a consistent description of the equation of state requires a temperature-dependent degeneracy $g(T)$ and an effective chemical potential $\mu(T)$. Within this approach, the trace anomaly (the trace of the energy-momentum tensor), i.e. the measure of nonconformality of the energy-momentum tensor normalized to $T^4$, is naturally reproduced together with its peak structure near the crossover region. The effective chemical-potential sector becomes particularly important in baryon-rich matter, whereas for the mesonic sector a separate dynamical description of the degrees of freedom is required.

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hep-ph 2026-05-13 Recognition

Off-shell graphs let parton showers reach order α_s²

Formulation of parton shower evolution beyond leading order for electron-positron annihilation

New Feynman graph representation enables splitting functions beyond leading order for e+e- collisions.

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Parton shower evolution is given by a renormalization group equation that reflects the infrared behavior of perturbative QCD including color and spin and including quantum interference. With added approximations, such an evolution equation can provide the basis for a parton shower event generator. To date, splitting functions for parton shower evolution have been derived only to leading order in $\as$. We provide a framework that can provide splitting functions beyond leading order, and in particular at order $\as^2$. This requires a representation of Feynman graphs in which partons are off shell and are characterized by vector or spinor indices instead of on-shell spins.

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hep-ph 2026-05-13 2 theorems

Model fits temperature and times to match Y suppression in Pb-Pb

In-medium Y(1S,2S,3S) suppression in Pb-Pb collisions at sqrt(s_NN)=5.02 TeV

Simultaneous chi^2 adjustment to CMS data reproduces the sequential centrality and momentum patterns for all three states.

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We present model calculations for the in-medium suppression of the Y(1S,2S,3S) states in sqrt(s_NN)=5.02 TeV Pb-Pb collisions at the Large Hadron Collider in comparison with recent CMS data for all three spin-triplet s-wave states. The model parameters initial central temperature, and formation times for the Y(nS) states are determined in simultaneous chi^2 minimizations with respect to the data, such that the sequential centrality- and transverse-momentum-dependent suppression of the observed states is reproduced.

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hep-ph 2026-05-13 Recognition

SMEFT in top decays alters ttH observable shapes at NLO

SMEFT everywhere: a NLO study of boldsymbol{pp to tbar{t}H} with decaying tops

Consistent NLO treatment with four dimension-6 operators changes distributions measured in LHC Run III data.

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We present the computation of the next-to-leading order QCD corrections to the $pp\to t\bar{t} H+X$ process in the di-lepton channel at the LHC, including relevant dimension-6 operators $({\cal O}_{t\phi}, \, {\cal O}_{\phi G},\, {\cal O}_{tG}, \, {\cal O}_{tW})$ from the Standard Model Effective Field Theory. In our studies, higher-order corrections and effective operators are consistently included in the production part of the process as well as in the top-quark decays. We perform a detailed study of linear, cross, and quadratic contributions and their uncertainties, including renormalisation group effects. Our findings are presented at the integrated and differential cross-section level for the LHC Run III center-of-mass energy of $\sqrt{s}=13.6$ TeV. Finally, we provide predictions for $pp\to t\bar{t} H+X$ with stable top quarks and compare them with the results in which top quarks are reconstructed from their decay products. We show that kinematic cuts, as well as higher-order effects and SMEFT operators in top-quark decays, are important and should be consistently considered together, because they have a significant impact on the shape of the standard observables measured for the $pp\to t\bar{t}H+X$ process at the LHC.

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hep-ph 2026-05-13 2 theorems

STCF extends sterile neutrino limits by 10-100 times

Long-lived sterile neutrinos from axionlike particles at the Super Tau-Charm Facility

via displaced-vertex searches for heavy neutral leptons from axionlike particle decays in D-meson decays at 3.773 GeV.

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We study the search prospect of long-lived heavy neutral leptons (HNLs) pair produced in decays of axionlike particles (ALPs) at the proposed Super Tau-Charm Facility (STCF), focusing on the center-of-mass energy of $\sqrt{s}=3.773$ GeV. The ALPs are assumed to originate from $D^\pm$-meson decays in association with a charged pion. We perform both truth-level and detector-level Monte Carlo simulations and obtain the expected sensitivity reach to the mixing parameter between the HNL and the electron neutrino, $|V_{eN}|^2$, with a displaced-vertex search at STCF. We find that STCF can probe values of $|V_{eN}|^2$ about one-to-two orders of magnitude beyond the existing bounds. We also perform an approximate reinterpretation of a search for HNLs at the CHARM experiment, which is subject to model-dependent assumptions on the production and kinematic distributions, and find that beam-dump experiments may provide strong complementary constraints.

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hep-ph 2026-05-12 2 theorems

Slow reheating revives black hole formation after supercooling

Reviving primordial black hole formation in slow first-order phase transitions

An early matter era lets small curvature perturbations collapse into spinning primordial black holes.

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Large curvature perturbations generated during slow first-order phase transitions are a promising source of primordial black holes. However, recent analyses suggested that the mechanism is ruled out once the density contrast and the formation threshold are evaluated in the same gauge. In this work, we show that this mechanism remains viable: after a supercooled transition, reheating can be sufficiently slow that the Universe enters an early matter-dominated era, during which even small overdensities grow and collapse into primordial black holes. An interesting feature of this scenario is that the black holes are produced with large spins.

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hep-ph 2026-05-12 Recognition

Interstellar hydrogen absorbs gravitons and emits excess photons

Detection of Gravitons: Graviton Absorption and Excess of Photon Luminosity from Interstellar Hydrogen

The surplus photon output from space hydrogen clouds would serve as indirect evidence for gravitons from stellar cores.

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We compute the graviton absorption and emission rates by hydrogen atoms in line with the results obtained by Weinberg, Gould, Dyson and other authors. The spontaneous emission of gravitons by the hydrogen atoms has a tiny undetectable rate, while the absorption rate of gravitons is much higher and is proportional to the number of hydrogen atoms and to the graviton luminosity. The graviton luminosity of Sun, or a typical star, is induced by the scattering of electrons and protons in a completely ionised hydrogen plasma at the core of the Sun and their energies are in the eV to keV range. We suggest measuring the excess in the ratio of the photon luminosities from interstellar hydrogen atoms that is induced due to the absorption of gravitons. The excess in the ratio of photon luminosities would indicate the presence of gravitons.

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hep-ph 2026-05-12 Recognition

Most gluon entanglement created by dynamics after quark removal

Gluon Entanglement Entropy inside a Nucleon: A Toy Model

In the lattice toy nucleon, time evolution supplies the bulk of the final entropy rather than the initial configuration.

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We construct a toy model of a nucleon, in which three static quarks interact via a SU(3) gauge field on a planar honeycomb lattice. The dynamics of the gauge field is described by the Kogut-Susskind Hamiltonian, truncated to the lowest three SU(3) irreducible representations. We show that the internal structure of the toy nucleon reflects salient features of the physical nucleon state. We then find the entanglement entropy of the gauge field within the nucleon state and compute its time evolution after a quench, in which all three valence quarks are suddenly removed. We show that the entanglement entropy in the final state is dominated by the dynamically generated contribution rather than the initial state entropy.

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hep-ph 2026-05-12 2 theorems

Approximate formula gives NBD entropy to 20% at extremes

An approximate formula for the entropy of the negative binomial distribution

Simplifies entropy calculations for charged particle multiplicities when parameters take extreme values

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Recent theoretical developments revived the interest in charged particle multiplicities and their wide-spread parametrization, the negative binomial distribution (NBD). The central observable of the studies is the Shannon entropy of the NBD. A closed form is not known, however, there are representations with special series and integrals. In this note, we will investigate one of these and give an approximate formula for the entropy that is valid up to $\sim$20\% deviation from the exact value for extreme values of the NBD parameters.

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hep-ph 2026-05-12 2 theorems

Δ(54) model unifies neutrino masses

Connecting Neutrino Masses, Dark Matter and Leptogenesis from Delta(54) Flavor with Triple Inverse Seesaw

Triple inverse seesaw under flavor symmetry fits oscillation data and yields observed baryon asymmetry for 10 TeV right-handed neutrinos.

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In this present study, an extended Delta 54 flavor symmetry model incorporating two standard model Higgs doublets is investigated. This model generates neutrino masses through the triple inverse seesaw mechanism. It predicts deviations from tribimaximal mixing, yielding a nonzero reactor angle and an atmospheric mixing angle in the upper octant. In addition, the CP-violating phase and the Jarlskog invariant are found to be consistent with current neutrino oscillation data. Our study also includes the dark matter sector by evaluating the relic abundance and active neutrino dark matter mixing under relevant cosmological constraints. Furthermore, baryogenesis is achieved through resonant leptogenesis at the TeV scale including flavor effects. We obtain the observed baryon asymmetry, for right-handed neutrino mass 10 TeV and mass splitting d.

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hep-ph 2026-05-12 Recognition

Modular S4 symmetry generates two-loop neutrino masses

Two-loop neutrino mass model with modular S₄ symmetry

Remnant Z2 symmetry stabilizes dark matter and fits normal-ordering oscillation data.

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We propose a two-loop radiative neutrino mass model based on the modular $\Gamma_4 \simeq S_4$ flavour symmetry supplemented by a discrete $Z_3$ symmetry. After spontaneous modular symmetry breaking, a remnant $Z_2$ symmetry guarantees both the radiative origin of active neutrino masses and stabilizes dark matter candidates. The model successfully reproduces charged lepton masses and neutrino oscillation data for normal ordering. It also predicts observable rates for charged lepton flavour violation (LFV). Due to the singlet-doublet mixing the model provides a viable scalar dark matter candidate. A fermionic dark matter candidate, strongly linked to LFV, is also present. We identify parameter regions consistent with relic density, LFV constraints, and direct detection limits, providing testable benchmark configurations.

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hep-ph 2026-05-12 2 theorems

Dark matter fermion sources lepton flavor violation

Dark Matter as a Source for Lepton Flavor Violation

A fermion candidate matches relic density and bounds while generating detectable muon-to-electron transitions.

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We will witness enormous progress in the experimental sensitivity to charged-lepton-violation processes in the near future. New physics signals of charged lepton violation might be around the corner without conflicting with existing astrophysical and accelerator bounds. In this work, we explore the possibility of having a dark matter particle as a source for $\mu\to e \gamma$, $\mu \to 3e$, and $\mu\to e$ conversion in nuclei. After computing the dark matter relic density and dark matter-nucleon scattering cross section, we outline the region of parameter space where one can simultaneously accommodate a dark matter fermion in agreement with existing collider and direct detection bounds, and positive signals in charged lepton violation observables.

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hep-ph 2026-05-12 2 theorems

SQUID at flux sweet spot scans axions over 15 mass orders

An ultra-broadband axion dark matter experiment

Quadratic voltage response plus lock-in modulation yields mass-independent sensitivity down to 10^{-16} GeV^{-1}

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We propose a novel broadband strategy to search for axions by leveraging observables controlled by the axion field squared. We present a practical implementation of this concept for probing the axion--photon coupling. This is done by operating a dc SQUID at the flux sweet spot, where the voltage depends quadratically on the magnetic flux, and using lock-in modulation to evade low-frequency noise. The proposed setup is ultra-broadband, spanning over 15 orders of magnitude in axion mass, with further expansion of the mass range possible. The projected sensitivity is $|g_{a\gamma\gamma}| \gtrsim 10^{-16} \text{ GeV}^{-1}$, orders of magnitude better than current bounds, and largely independent of axion mass. We discuss the sources of systematic background and a nulling technique to reduce them to an acceptable level. We also discuss how our strategy could be adapted to probe the axion-fermion coupling, as well as to detect other dark matter candidates such as dark photons.

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hep-ph 2026-05-12 2 theorems

LHC timing can double sensitivity to new physics signals

Time-dependent signals of new physics at the LHC

Time variations from ultralight dark matter give an extra way to distinguish signals from constant backgrounds.

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The Large Hadron Collider (LHC) is sensitive to signals of beyond the Standard Model physics through a variety of channels including missing energy and resonance searches. In most searches, the new physics and the Standard Model backgrounds are assumed to be invariant in time, up to systematic effects from the experiment. However, new physics with a time variation would provide an additional handle to separate signal from background. Such a time variation may come from ultralight dark matter coupling to an oscillating background field. In this paper, we consider an interaction of dark matter with quarks and an additional heavy particle, and show that the sensitivity of a search that uses timing information at the LHC can be up to a factor of two stronger compared to one that does not use time information.

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hep-ph 2026-05-12 Recognition

Electron detectors reach light dark matter via wide mediator range

Electronic Direct Detection of Light Dark Matter with Intermediate-Mass Mediators

For sub-GeV dark matter from freeze-in, the gap between light and heavy mediator limits spans up to three orders of magnitude in mass.

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Recent years have seen dramatic improvements in the sensitivity of electron-based direct detection experiments. Typically, the sensitivity to dark matter scattering is determined in the light and heavy mediator mass limits. In this paper we show that the light and heavy mediator mass limits are not separated by a single scale, but instead can be separated by up to three orders of magnitude in mediator mass for sub-GeV mass dark matter. We calculate the background-free sensitivity in Si and Ge targets, and a projected DAMIC-M sensitivity, to sub-GeV mass dark matter models with ``intermediate-mass" mediators between the light and heavy mediator limits. This allows us to determine the precise range of mediator masses that electron-based direct detection experiments are sensitive to when the dark matter relic abundance is generated via freeze-in. We make the calculations presented here publicly available in an updated release of EXCEED-DM (https://github.com/tanner-trickle/EXCEED-DM).

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hep-ph 2026-05-12 2 theorems

Inflation limits gravitational neutrino production to Y < 10^{-11}

Neutrino mixing and gravitational production via inflation

Time-dependent mixing from scalar fluctuations boosts production but keeps abundance low for active and sterile neutrinos.

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We develop the Bogolyubov coefficient formalism for gravitational production of fermions with time-dependent mixing, which allows us to study a prototype neutrino system. The neutrino masses and mixings depend on the scalar field values, i.e. the Higgs or singlet scalar expectation values. These are time-dependent in the Early Universe and, due to de Sitter fluctuations, can reach very large values during inflation. As a result, gravitational production of all types of neutrinos can be much enhanced. We obtain an upper bound on the abundance of active and sterile neutrinos produced by classical gravity, $Y \lesssim 10^{-11}$.

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hep-ph 2026-05-12 Recognition

Cancellations suppress ψ(4040) D D-bar decay

Nodal mechanism for the suppressed Dbar D decay of psi(4040) in the Bethe--Salpeter framework

The overlap integral nearly cancels for D D-bar but spares D D-star and D_s D_s-bar in the conventional charmonium picture.

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The strong decay $\psi(4040)\to D\bar D$ is anomalously suppressed despite ample phase space, whereas the $D\bar D^*$ and $D_s\bar D_s$ channels remain sizable. In this work, we study this suppression and the associated open-charm hierarchy in the framework of the instantaneous Bethe--Salpeter equation combined with the relativistic $^3P_0$ model, with the pair-creation strength fixed independently from $\psi(3770)\to D\bar D$. Within this framework, we show that the suppressed $D\bar D$ mode can be understood as a consequence of node-induced cancellations in the relativistic decay amplitude. The $D\bar D$ amplitude is strongly reduced because the corresponding overlap integral receives comparable positive and negative contributions from different momentum regions, whereas the $D\bar D^*$ and $D_s\bar D_s$ channels do not undergo the same strong cancellation. This interpretation is further supported by the pronounced sensitivity of the $D\bar D$ width to the initial mass, the charged-neutral $D$-meson mass splitting, and the dip structure in the mass dependence of the partial width. Our results provide a dynamical explanation of the suppressed $D\bar D$ mode and the core open-charm hierarchy of $\psi(4040)$ within a conventional $3\,{}^3S_1$ charmonium picture, while the precise value of the near-vanishing $D\bar D$ width remains model dependent.

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hep-ph 2026-05-12 Recognition

Unitarized model merges gluon PDF moments with trace anomaly for J/ψ photoproduction

Unitarized Matching of Gluon PDF Moments and the QCD Trace Anomaly in Near-Threshold J/psi Photoproduction

Scalar form factor survives unitarization and links threshold data to high-energy Pomeron regime over three orders of magnitude in energy.

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We construct a framework for near-threshold $J/\psi$ photoproduction that combines a target-mass-corrected gluon-PDF moment expansion with an explicit scalar gravitational form factor associated with the QCD trace anomaly. Both contributions are embedded into a common partial-wave K-matrix unitarization scheme, ensuring elastic unitarity at the amplitude level. The resulting hierarchy of nested models is tested against GlueX data and shown to produce distinct signatures in the differential cross section, the effective $t$-slope, and the real-to-imaginary ratio. The scalar form-factor signal is found to be robust against PDF-set variations and survives unitarization. A smooth matching to the Pomeron power-law regime at high energy is demonstrated, providing a unified description from threshold to HERA energies spanning three orders of magnitude in the center-of-mass energy.

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hep-ph 2026-05-12 2 theorems

VBF jets separate Higgs portal from neutralino dark matter

Distinguishing Higgs portal and neutralino dark matter via vector boson fusion

Softer jet momenta and different angular gaps in two-jet plus missing energy events allow over 5 sigma distinction at the LHC.

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Understanding the nature of dark matter (DM) is a fundamental challenge in particle physics. In this paper, we investigate the potential of vector boson fusion (VBF) processes at the Large Hadron Collider (LHC) to demonstrate, as a proof of principle, the feasibility of distinguishing between different dark matter scenarios, focusing on Higgs portal DM (HPDM) and neutralino DM in the $2j + \not\!\! E_T$ final state and exploiting the distinctive kinematic features of the VBF jets and the missing transverse energy. Our study reveals that the polarization of weak bosons in VBF plays a crucial role in shaping the transverse momentum distributions of the tagged jets, with the jets being less energetic in the transverse direction for the Higgs portal scenario compared to the neutralino scenario. In addition, the kinematic variables $\Delta\eta$ and $\Delta\phi$ exhibit characteristic differences between the Higgs portal and neutralino DM signals, providing significant discriminating power between these scenarios. We further apply a Kolmogorov--Smirnov test using linear discriminant analysis to quantify the distinguishability of the signals and find that the Higgs portal signals can be differentiated from neutralino DM signals with a C.L. exceeding $5\sigma$, thereby establishing the viability of collider-based discrimination between dark matter models.

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hep-ph 2026-05-12 2 theorems

Reactor neutrinos support X17 particle

The X17 Existence Hinted at by Nuclear Reactor Neutrinos

CEvNS data from CONUS+ and Dresden-II fit the couplings needed to explain the ATOMKI nuclear anomaly.

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We show how, by exploiting the process of Coherent Elastic neutrino (v) Nucleus Scattering (CEvNS), neutrinos produced by nuclear reactor experiments appear to corroborate the evidence of the so-called X17 particle, which has been invoked to explain the ATOMKI anomaly. We base our analysis primarily on CONUS+ and Dresden-II data, which, when combined with CEvNS data from COHERENT and neutrino oscillation data from IceCube, single out a unique region of couplings to neutrinos and nuclei.

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hep-ph 2026-05-12 1 theorem

Heavy-quark condensate computed to five loops

Heavy-Quark Condensate and Vacuum Energy Anomalous Dimension at Five Loops

First QCD result with finite quark masses confirms vacuum energy anomalous dimension at high order.

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We present the perturbative heavy-quark condensate at five-loop order in QCD. This constitutes the first calculation at this order accounting for non-vanishing quark masses. Our result confirms the computation of the five-loop vacuum anomalous dimension by Baikov and Chetyrkin.

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hep-ph 2026-05-12 2 theorems

Unitarized FSI improves large-Nc ChPT fit to η' → ηππ data

Study of η^prime to η ππ Decays in Large-N_C Chiral Perturbation Theory

NNLO amplitudes with S- and D-wave ππ rescattering yield Dalitz parameters a=-0.085, b=-0.081, d=-0.045 that match A2 measurements.

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We investigate the $\eta^\prime \to \eta \pi\pi$ decays within the framework of large-$N_{C}$ chiral perturbation theory, by calculating the decay amplitudes up to next-to-next-to-leading order in a simultaneous expansion in powers of external momenta, quark masses, and $1/N_C$. Projecting the amplitudes onto partial waves allows us to implement a unitarization procedure to account for the $S$- and $D$-wave $\pi\pi$ final-state interactions. The relevant low-energy constants are determined by fitting our theoretical results to the precise experimental data from the A2 collaboration. A comparison of fits with and without $\pi\pi$ final-state interactions demonstrates that including these effects significantly improves the agreement of our theoretical predictions with the experimental measurements. Consequently, the Dalitz-plot parameters are extracted as $a=-0.085(18)_{\mathrm{stat}}(4)_{\mathrm{syst}}$, $b=-0.081(10)_{\mathrm{stat}}(6)_{\mathrm{syst}}$, and $d=-0.045(6)_{\mathrm{stat}}(8)_{\mathrm{syst}}$. Our results provide therefore a refined theoretical description of the $\eta^\prime \to \eta \pi\pi$ decay dynamics.

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hep-ph 2026-05-12 1 theorem

Dark matter admixture shifts neutron star ringdown frequencies

Axial Quasi-normal Modes of Admixed Neutron Stars

Axial quasi-normal modes change with dark matter fraction and can cross into boson-star behavior, offering a gravitational-wave probe of the

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We study axial quasi-normal modes of admixed neutron stars composed of ordinary nuclear matter and a self-interacting bosonic dark matter component. The equilibrium configurations are obtained by solving the coupled two-fluid Tolman-Oppenheimer-Volkoff equations, where the neutron sector is modeled with several realistic equations of state and the bosonic sector is described by a repulsively self-interacting complex scalar field in the strong-coupling regime. We analyze linear axial perturbations governed by a Regge-Wheeler type equation whose effective potential reflects the combined matter distribution. Using a continued-fraction method, we compute the complex eigenfrequencies of the fundamental and overtone $w$ modes. We obtain the quasi-normal mode spectrum and investigate its dependence on the dark matter particle mass, self-coupling, and the central densities of both fluids for several realistic neutron star equations of state. We find that increasing the dark matter fraction shifts the oscillation frequencies and damping times. It can also reorder the mode hierarchy through crossings, and it drives a continuous transition from neutron star-like to boson star-like ringdown behavior. Our results demonstrate that the ringdown gravitational-wave signal from post-merger compact objects could encode clear imprints of a dark matter component, offering a new probe of the dark sector with future gravitational-wave observatories.

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hep-ph 2026-05-12 Recognition

New generator simulates doubly heavy baryon events at e+e- colliders

EEXICC: An event generator for doubly heavy baryon production at e^+e^- colliders

EEXICC applies an improved amplitude trace method in NRQCD to produce Ξcc, Ξbc and Ξbb events faster than squared-amplitude codes and works,

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We present EEXICC, a Monte Carlo event generator designed to simulate the production of doubly heavy baryons ($\Xi_{cc}$, $\Xi_{bc}$, and $\Xi_{bb}$) via $e^+e^-$ annihilation. Based on nonrelativistic QCD effective theory, the generator calculates the process $e^{+}+e^{-}\rightarrow \Xi_{QQ'}+\bar{Q}'+\bar{Q}$ using an improved trace technique at the amplitude level, which greatly improves numerical efficiency compared with traditional squared-amplitude methods. EEXICC is developed in Fortran with a modular structure and is fully compatible with the PYTHIA framework, enabling convenient integration into complete event simulation workflows. The program supports both weighted and unweighted event generation, and its numerical reliability has been verified against existing theoretical results. EEXICC provides a flexible and robust tool for studying the properties of doubly heavy baryons at future high-luminosity and high-energy $e^+e^-$ colliders such as the CEPC and FCC-ee.

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hep-ph 2026-05-12 2 theorems

RG-consistent PNJL improves match to lattice baryon fluctuations

RG-Consistent (P)NJL Model: Impact of Thermal Cutoff Modifications on Thermodynamics and Net-Baryon Number Fluctuations

Temperature-dependent cutoff removes causality violations and brings kurtosis ratio closer to lattice values at zero density.

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In this paper, we investigate the impact of renormalization group (RG) consistency on the chiral phase transition and thermodynamic properties of QCD matter using the RGNJL and RGPNJL models. By implementing a temperature-dependent thermal cutoff $\Lambda_T = k\Lambda_0$, we ensure that thermodynamic quantities converge toward the Stefan-Boltzmann limit at high temperatures, effectively extending the applicability of these effective theories. Our analysis shows that while the RG-consistency condition ($k \rightarrow \infty$) resolves causality violations in the RGNJL model by binding the speed of sound to the conformal limit, the RGPNJL model exhibits a more complex, non-monotonic sensitivity to the parameter $k$. Furthermore, we demonstrate that the RG-improved PNJL framework significantly enhances the description of net-baryon number fluctuations ($\kappa\sigma^2$) relative to lattice QCD data at vanishing chemical potential, though the intensification of these fluctuations at high baryon density highlights a critical sensitivity to the model's parametric constraints. This study provides a rigorous evaluation of the RG-consistency framework's predictive power in mapping the QCD phase diagram and interpreting experimental observables.

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hep-ph 2026-05-12 Recognition

Quark broadening in Glasma scales with saturation momentum

Light-front Hamiltonian jet evolution in the Glasma

Light-front evolution reproduces classical jet quenching estimates and supplies a basis for adding quantum splittings later.

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We develop a light-front Hamiltonian formalism to study the real-time quantum evolution of a high-energy quark propagating through the Glasma phase of a heavy-ion collision. In this work, the quark Fock space is truncated to the $\ket{q}$ sector and the wavefunction is expanded in a discrete basis representation, following the time-dependent Basis Light-Front Quantization (tBLFQ) framework. The classical Glasma background fields enter as a time-dependent external potential, and physical observables are extracted as expectation values of quantum operators over the time-evolved state. We compute the transverse momentum broadening and the jet quenching parameter, finding results consistent with classical estimates, including the expected scaling with respect to the saturation momentum, and use them to perform phenomenological estimations for different collision systems. We also study the color rotation of the quark state induced by the Glasma fields, and examine its dependence on the saturation scale and the gauge choice. This formalism allows systematic improvements to include, in particular, non-eikonal propagation and parton splittings that will be considered in forthcoming publications.

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hep-ph 2026-05-12 Recognition

2023 flux model revives reactor antineutrino anomaly at 2.2 sigma

Revival of the Reactor Antineutrino Anomaly

Latest summation calculation shows 2.2 sigma deficit in reactor rates, creating 3.8 sigma tension with gallium data reducible to 1.3 sigma

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The Reactor Antineutrino Anomaly refers to the deficit observed between the average event rate measured in reactor antineutrino experiments with respect to the theoretical prediction. This anomaly was first identified in 2011 ($2.5\sigma$) as a consequence of the Huber-Muller reactor antineutrino flux calculation. It was thought to be resolved in 2021 as a result of new reactor antineutrino flux calculations, with a reduction to about $1 \sigma$. In this work, we examine the latest reactor antineutrino flux calculation published in 2023 by a French research group. This work represents the first summation model to include a comprehensive uncertainty budget. The result indicates a revival of the Reactor Antineutrino Anomaly at the level of $2.2\,\sigma$. We also consider the usual simplest explanation of the Reactor Antineutrino Anomaly by active-sterile neutrino oscillations. We present the constraints on the oscillation parameters and we derive a tension of $3.8\sigma$ with the results of gallium source experiments (Gallium Anomaly) taking into account also the solar neutrino and KATRIN bounds, that of the combined short-baseline reactor spectral ratio measurements, and that of the Daya Bay search for a sub-eV sterile neutrino. Since the tension may be due to underestimated systematic uncertainties and the main tension is between the gallium data and the other data, we finally present the results of a global analysis with enlarged gallium uncertainties, which reduce the global tension to $1.3\sigma$.

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hep-ph 2026-05-12 Recognition

Fast quenches produce mean-field scaling across first-order transitions

Non-equilibrium scaling across first-order transitions with relativistic scalar fields

Relativistic Z2 scalar fields under rapid linear driving show temperature-independent finite-time scaling that crosses over to Kibble-Zurek

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We investigate the out-of-equilibrium dynamics of a relativistic $Z_2$-symmetric scalar field theory with Langevin dynamics in two and three spatial dimensions under linear driving across magnetic first-order phase transitions, close to and far below the critical temperature $T_c$. Using classical-statistical lattice simulations, we find that if the driving timescale is sufficiently fast, the system exhibits finite-time scaling behavior independent of temperature and dimensionality, identical to that observed in mean-field simulations. In slow quenches near $T_c$ this mean-field behavior crosses over to critical Kibble-Zurek scaling behavior, while for temperatures $T \ll T_c$ nucleation and growth dominate the transition dynamics, resulting in corrections to scaling. Near the transition point where the order parameter changes sign, the crossover between mean-field and critical out-of-equilibrium dynamics is found to be well described by the leading algebraic correction to Kibble-Zurek scaling. We find that universal non-equilibrium scaling behavior can be observed for $T \lesssim T_c$, provided the driving is fast enough to avoid nucleation but slow enough for correlations to form, and compute the associated universal scaling functions for the order parameter.

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hep-ph 2026-05-12 2 theorems

Hydrogen PNC ratio to SM grows faster than 1/Z² for light Z'

Parity Nonconservation in Hydrogen Induced by Low-Mass Vector-Boson Exchange

The relative size of a low-mass extra vector boson signal increases rapidly as nuclear charge drops, offering cleaner separation from the Z-

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Parity-nonconserving (PNC) effects in atoms produced by $Z$-boson exchange between the electron and the nucleus grow rapidly with the nuclear charge $Z$. If a hypothetical additional $Z'$ boson is light, however, its contribution does not exhibit the same strong enhancement with $Z$. As a result, the ratio of the low-mass $Z'$ contribution to the Standard Model $Z$-boson contribution increases rapidly with decreasing $Z$, in fact faster than $1/Z^2$. Hydrogen has a further important advantage: its theoretical description is substantially cleaner than that of heavy atoms, allowing a more accurate interpretation of experimental results. For these two reasons, hydrogen and deuterium PNC experiments may provide an especially favorable setting in which to disentangle a possible $Z'$ contribution from the Standard Model background. In this paper we calculate the ratio of the $Z'$-boson contribution, for arbitrary $Z'$ mass, to the Standard Model $Z$-boson contribution to parity violation in hydrogen and deuterium, including both nuclear-spin-independent (NSI) and nuclear-spin-dependent (NSD) interactions.

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hep-ph 2026-05-12 2 theorems

Spin-1 resonances viable at 1.5 TeV in composite Higgs models

Phenomenology of electroweak spin-1 resonances

Models with unbroken SU(2)_L x SU(2)_R symmetry predict singly producible states that current data still allow.

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Composite Higgs models with a fermionic UV completion predict the existence of various bound states. We investigate models containing SU(2)$_L\times$SU(2)$_R$ as part of the unbroken global subgroup in the new strong sector. These models predict that there are two neutral and one charged spin-1 resonances mixing seizable with the SM vector bosons. These can be singly produced at the LHC. We explore their LHC phenomenology and demonstrate that there are still viable scenarios consistent with existing LHC data where the masses of these states can be as low as about 1.5 TeV.

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hep-ph 2026-05-12 2 theorems

Closed-form zeta(3) term found for four-loop non-singlet quark anomalous dimension

Four-loop anomalous dimension of flavor non-singlet quark operator of twist two and Lorentz spin N for general gauge group: transcendental part

Exact expressions for arbitrary spin N yield precise x-space splitting functions and lower approximation uncertainties

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Both for quark flavor asymmetry and valence, we consider the anomalous dimension of the non-singlet twist-two quark operator of arbitrary Lorentz spin N at four loops in SU(nc) color gauge theory and present its term proportional to zeta(3) in closed form. These results have been extracted from published Mellin moments, for N=1,...,16 and N=3,...,15, respectively, by analytic reconstruction using advanced methods of number theory. Via Mellin transformation, we obtain the exact functional forms in x of the respective pieces of Dokshitzer-Gribov-Lipatov-Altarelli-Parisi splitting functions. This allows us to reduce the theoretical uncertainties in the approximations of these splitting functions otherwise amenable from the first few low-N values.

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hep-ph 2026-05-12 Recognition

Compact cycle predicts tau mass of 1776.97 MeV

Charged-Lepton Koide Geometry from a Green-Dressed Compact Family Cycle

A single real amplitude on an internal circle with Berry dressing from spinor reality condition fixes the charged-lepton mass vector.

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Koide's charged-lepton relation suggests that $(\sqrt{m_e},\sqrt{m_\mu},\sqrt{m_\tau})$ is the natural family vector. We construct an effective compact-cycle model in which this vector is sampled from one real amplitude $Z(\phi)$ on an internal circle, while the masses are quadratic overlaps, $m_a\propto |Z(2\pi a/3)|^2$. The amplitude is built from the two lowest antiperiodic modes on the circle; their symmetric square is periodic and gives the minimal three-harmonic family space $e^{i\phi},1,e^{-i\phi}$. A reality condition together with the requirement that the amplitude comes from the square of one two-component spinor fixes the relative weights required by Koide's $45^\circ$ geometry. The remaining orientation angle is fixed by matching one $C_3$ family shift to transport on the full circle: integrating out the higher Fourier harmonics gives the Berry dressing that enters the determinant term and selects $\theta_\ell=-2/9$. Using $m_e$ and $m_\mu$ as inputs, the model predicts $m_\tau=1776.97\,\mathrm{MeV}$.

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hep-ph 2026-05-12 2 theorems

Local branch data fix controlled penumbral inflation

Controlled Penumbral Inflation from Monodromic Valleys

A parameter condition on the effective theory splits valleys into controlled, uncontrolled or none, with an exactly solvable example that is

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Long monodromic valleys arise in the penumbra of complex-structure moduli space. We show that their local branch data already determine whether they support controlled inflation, and thereby isolate the first controlled penumbral inflationary window. In the axion--saxion effective theory given in Eq.4, a branch-displacing odd term generates a plateau when $\Delta\equiv p+2\nu-q>0$, while covariant single-clock control further requires $p<2$, or $p=2$ with $12A_pm^2/V_0\gg1$ over the observational window. This splits penumbral valleys into no plateau, uncontrolled plateau, and controlled plateau before global completion is attempted. We identify a minimal analytic family with a closed-form valley and an invariant attractor equation for the full two-field dynamics, providing the first exactly solvable penumbral realization that remains predictive under the next penumbral order. The penumbra is thus promoted from a geometric suggestion to a predictive search principle.

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hep-ph 2026-05-12 2 theorems

Method reconstructs rare particle sources without Gaussian assumptions

Reconstructing rare particle source by femtoscopic correlations

Uses particle-by-particle kernel averages to extract single-particle emission profiles for low-yield particles like J/ψ with 13% uncertainty

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Measurement of particle emission source is a fundamental objective of femtoscopy in high-energy nuclear collisions. Conventional analyses rely on Gaussian parameterizations of pair emission sources, which makes the extraction of single-particle emission sources challenging, particularly for rare particles. Here, we introduce a novel Statistical Reconstruction method that allows extracting information of target single-particle sources relative to a data-constrained reference source instead of the Gaussian assumption. The correlation function is expressed as an ensemble average over single-particle-conditioned correlation kernel, defined as the particle-by-particle contribution to the correlation function conditioned by the target particles. For particles with rare yeilds, the particle-by-particle distribution of this kernel can be transformed into event-by-event extraction and becomes experimentally accessible, enabling a direct statistical reconstruction of the single-particle emission source, instead of inferring a pair source. We apply this method to reconstruct $J/\psi$ source via $p-J/\psi$ correlations, using HAL QCD-derived $NJ/\psi$ potentials in $\sqrt{s}=13.6$~TeV $pp$ collisions simulated with EPOS4HQ. The reconstructed source reproduces the key characteristics and this new approche achieves a systematic uncertainty of approximately $13\%$ based on EPOS4 simulation.

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hep-ph 2026-05-12 Recognition

Scalar mediator boosts dark photon annihilation to fit gamma excess

Higgs-Portal Spin-1 Dark Matter with Parity-Violating Interaction for a Galactic Halo Gamma Ray Excess

A 400 MeV CP-even scalar creates Sommerfeld enhancement in the halo for 420 GeV dark matter while preserving freeze-out and dwarf-galaxy p-

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We study a dark photon dark matter scenario associated with a gauged $U(1)_X$ symmetry, stabilized by a dark parity that forbids kinetic mixing with the Standard Model. The leading interactions between the dark photon dark matter and the Standard Model arise from dimension-six Higgs-portal operators. In previous work, we found that for the parity-violating operator, the dark matter annihilation process is $p$-wave suppressed, naturally evading stringent direct-detection constraints while reproducing the observed relic abundance through thermal freeze-out. For a cutoff scale of 1 TeV, a dark matter mass of around 400 GeV is favored to realize the observed relic abundance. This scenario predicts cosmic-ray signals, in particular in the $W^{+}W^{-}$ channel, which can be targeted by indirect-detection experiments. Recently, a halo-like gamma-ray excess has been reported by Totani. Assuming a Navarro--Frenk--White $-\rho^2$ morphology for the dark matter distribution, a dark matter mass of 420 GeV is favored for the $W^{+}W^{-}$ final state. Motivated by this excess, we consider the present dark photon dark matter framework augmented by a CP-even scalar mediator with a mass of around 400 MeV, which couples to the dark photon mass operator in order to enhance the present-day annihilation rate in the Galactic halo without affecting the freeze-out dynamics. The exchange of this scalar induces a long-range attractive force, leading to Sommerfeld enhancement of the annihilation rate. The enhancement is saturating in dwarf spheroidal galaxies and the annihilation rate is dropping as $p$-wave remaining consistent with constraints from dwarf galaxies and cosmology.

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hep-ph 2026-05-12 2 theorems

Magnetized 7-branes on orbifold yield MSSM chiral spectrum

MSSM flavors from 7-brane configurations of magnetized SYM on R^{1,3} times (T²)³/(Z₂ times Z'₂)

Background fluxes preserve supersymmetry and generate hierarchical Yukawa couplings from wavefunction overlaps.

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We show that chiral matters in the minimal supersymmetric standard model (MSSM) with semi-realistic flavor structures can be obtained form 7-brane configurations of magnetized super Yang-Mills (SYM) theory on a toroidal orbifold $R^{1,3} \times (T^2)^3/(Z_2 \times Z'_2)$, where background magnetic fluxes and Wilson-lines are turned on preserving four-dimensional ${\cal N}=1$ supersymmetry. The zero-mode spectrum of chiral multiplets in total is just MSSM ones, except the existence of those for three generations of right-handed neutrino and extra generations of MSSM Higgs pairs. Hierarchical Yukawa couplings can be obtained from the overlap integrals of wavefunctions localized in extra dimensions, allowing semi-realistic patterns of flavor structures for quarks and charged leptons. We also develop a systematic way to embed additional 7-branes into the configuration, those are sequestered from the visible sector toward a hidden sector model building.

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hep-ph 2026-05-12 1 theorem

Six-head circuit explains most jet tagger performance

Dissecting Jet-Tagger Through Mechanistic Interpretability

Early source, middle relays on pairwise substructure, late readout recover bulk accuracy and align with energy correlators.

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Mechanistic interpretability seeks to reverse engineer a trained neural network by identifying the minimal subset of internal components. We perform a mechanistic interpretability analysis of the Particle Transformer architecture, trained on the Top Quark Tagging reference dataset, with the goal of identifying the computational circuit responsible for jet classification and characterizing the physical content of its internal representations. Combining zero ablation, path patching with two complementary on-manifold corruption strategies and linear probing of the residual stream, we identify a sparse six-head circuit that recovers the great majority of the full model performance while admitting a clean source-relay-readout interpretation. In this circuit, a single early layer head serves as the primary causal source, a cluster of middle-layer heads acts as relays selectively attending to hard pairwise substructure and a single late-layer head reads out the aggregated signal. Linear probes show that the residual stream is preferentially aligned with the energy correlator basis over the $N$-subjettiness basis. Within the energy correlator basis, the model preferentially encodes 2-prong substructure observables over the 3-prong observables. A per-layer trained probe further reveals that the apparent single step commitment of the model to a classification decision in the first class attention block is in fact a basis rotation, with the discriminating signal already saturating in the particle attention stack. These results demonstrate that mechanistic interpretability methods developed for natural language models can be used for jet physics classifiers and indicate that gradient descent may rediscover physically meaningful aspects of jet tagging without supervision.

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hep-ph 2026-05-12 3 theorems

Symmetry rules limit nucleon-pentaquark mixing to six channels

Chiral Structure and Selection Rules in Light-Front Nucleon-Pentaquark Mixing

Light-front calculation shows 21 of 27 states vanish, with five-quark probability reaching 29%.

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We present a light-front Hamiltonian analysis of nucleon-pentaquark mixing induced by $\sigma$- and $\pi$-type transition operators in a fully Pauli-consistent five-quark basis. The pentaquark configurations are constructed using a systematic permutation-group classification of orbital, spin-flavor, and color degrees of freedom, and the hyperfine interaction is diagonalized to obtain orthonormal eigenchannels with definite quantum numbers. We compute the mixing coefficients for all 27 positive-parity $P$-wave pentastates and find a highly sparse structure: only 6 channels contribute to the nucleon wave function, while the remaining 21 vanish due to symmetry selection rules. The nonzero contributions are concentrated in a small set of hyperfine eigenchannels, demonstrating a strong dominance pattern. The $\sigma$- and $\pi$-induced amplitudes populate the same subset of states and are related by a fixed phase, reflecting their common chiral structure, which eliminates interference in the normalization. As a result, their contributions add incoherently, yielding a total five-quark probability of about $29\%$, with the remaining $71\%$ residing in the three-quark core. These results show that nucleon-pentaquark mixing is governed primarily by symmetry selection rules and chiral structure, and that the five-quark content is dominated by a small number of dynamically selected channels.

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hep-ph 2026-05-11 3 theorems

Annihilation during inflaton decay produces dark matter

Asymmetric Reheating of Dark QED

Asymmetric reheating sets a temperature ratio that lets dark QED match the observed relic density even without full hidden-sector thermal eq

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We study in detail a scenario in which the inflaton scalar field couples to both a visible sector (VS) and a hidden sector (HS). The VS is assumed to contain the Standard Model (SM), while the HS contains a dark matter (DM) candidate. We are in particular interested in a scenario in which the inflaton decays dominantly into the HS degrees of freedom. The DM candidate is taken to be a dark Dirac fermion $\chi$, coupled to a massive dark photon $\gamma'$, a popular model for a HS also known as Dark QED. The inflaton decays into particles of both sectors generate an initial asymmetry between the SM and HS fermion abundances, which we model as being proportional to the ratio of effective Yukawa couplings, $y$ and $y'$. We pay particular attention to the process of thermalisation of the HS, with temperature $T'$, as a function of $y'$ and $\alpha'$, the HS fine structure constant. We investigate the several possible ways of producing the observed DM relic abundance, and their interplay with the reheating of the HS and the transfer of energy between the HS and the VS. Key results, beyond the systematic character of our analysis, include: a new mechanism for DM production, which occurs when DM particles annihilate while still being produced by the inflaton decay; a study of the temperature ratio $\xi = T'/T$ and its relation with the initial energy asymmetry between the HS and VS, as parameterized by $\xi_i = \sqrt{y'/y}$; a reassessment of the domain of viable DM candidates, taking into account the constraints set by unitarity and the thermalisation of the HS, accounting for the LPM effect; and, in cases where the HS does not reach thermal equilibrium, an analysis of how non-thermal DM production fits within the domain of thermal DM candidates.

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hep-ph 2026-05-11 2 theorems

Entanglement in Lambda_b decays extracts CKM gamma with precision 1/C

Spin-flavor entanglement in Λ_b to Λ D and weak phase extraction

Uncertainty on the weak phase scales inversely with the Wootters concurrence of the spin-flavor system.

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We identify a new spin-flavor entanglement structure in $\Lambda_b\to\Lambda D$ decays, formed by the correlation between the $\Lambda$ spin and the $D$ flavor states ($D=D^0,\overline D^0,D_1,D_2$). The entanglement information is encoded in the decay rates and Lee-Yang parameters of the four neutral-$D$ modes. We then show that the same spin-flavor structure provides a new method to determine the weak phase $\gamma$, a key angle of the Cabibbo-Kobayashi-Maskawa unitarity triangle. We find that the experimental uncertainty scales as $\sigma_\gamma\propto 1/{\cal C}$, where ${\cal C}$ is the Wootters concurrence, thereby quantitatively relating the precision of the weak-phase extraction to the amount of spin-flavor entanglement.

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hep-ph 2026-05-11 2 theorems

Koide ratio minimized at Q0/(1+Q0) by adding one mass

A minimization theorem for the Koide ratio and its Standard Model calibration

Theorem supplies lepton benchmark near 1.255 GeV; charm ranks high among SM particle seeds.

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The charged-lepton Koide relation remains a striking empirical regularity in Standard-Model flavor data. We prove that for any positive mass set with Koide ratio $Q_0$, the one-particle extension $Q(m_1,\ldots,m_N,x)$ has a unique global minimum $Q_\text{min}=Q_0/(1+Q_0)$ at $m^*=\bigl[(\sum_i m_i)/(\sum_i \sqrt{m_i})\bigr]^2$. This exact kinematic result defines a unique extension benchmark. For the measured charged leptons it gives $m_*^\ell = 1.255\,34(16)\,\text{GeV}$ and $Q_{4,\min}^{\mathrm{exp}} = 0.399\,997\,8(43)$; in the ideal Koide limit $Q_\ell^{\mathrm{K}}=2/3$, the corresponding minimum is exactly $2/5$. In the effective-participant language $N_{\mathrm{eff}}\equiv 1/Q$, the optimal one-particle extension increases $N_{\mathrm{eff}}$ by one, while the equal-$k$ multiplet extension increases it by $k$. The one-particle $N_{\mathrm{eff}}$ profile is exactly Lorentzian in a dimensionless share-mismatch coordinate $u$, which we interpret kinematically rather than dynamically. Using charged-lepton pole masses with the PDG~2024 own-scale $\overline{\text{MS}}$ charm mass gives $Q(e,\mu,\tau,c)=0.400\,002\,5(64)$, i.e. $11.7\,\text{ppm}$ above the measured-input benchmark and $6.2\,\text{ppm}$ above $2/5$. This intentionally mixed-definition comparison is treated only as a phenomenological coincidence. To calibrate it within a stated benchmark class, we perform an exhaustive common-scale scan over non-neutrino Standard Model 2-body and 3-body seeds with one added mass. The charged-lepton-plus-charm continuation ranks $33/12{,}720$ in the raw trial set, $24/2{,}640$ after collapsing repeated scale realizations, and $6/756$ within the fermion-only collapsed subset. We present the charm case as an empirically calibrated example of the theorem, not as a dynamical flavor model.

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hep-ph 2026-05-11 Recognition

Generating functions enable symbolic reduction of multi-loop integrals

An Algorithm for the Symbolic Reduction of Multi-loop Feynman Integrals via Generating Functions

Rewriting IBP identities as differential equations for sector generating functions produces an iterative algorithm that extracts rules and a

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We develop a generating-function formulation for the symbolic reduction of multi-loop Feynman integrals. In this framework, integration-by-parts identities are rewritten as differential equations for sector-wise generating functions, so the reduction problem can be studied in a non-commutative algebra of differential operators rather than only through relations among individual integrals. This viewpoint leads to an iterative algorithm that generates candidate equations, extracts symbolic reduction rules, updates the active rule set, and tests completeness on the lattice of integral indices. We illustrate the method with the sunset topology, planar and non-planar massless double-box topologies, representative subsectors, and a degenerate example in which the top sector contains no master integral. Together, these examples show how symbolic reduction rules, descendant equations, and completeness criteria can be organized within a single algebraic framework.

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hep-ph 2026-05-11 2 theorems

Non-factorisable EW corrections iterate the one-loop result at two loops

Non-factorisable electroweak virtual corrections to single-resonant processes

After decoupling heavy particles, two-loop non-factorisable terms equal the square of the one-loop result plus light-fermion loops and hold,

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We consider electroweak (EW) virtual corrections to $2\to 2$ fermion scattering processes mediated by a vector boson $V$ ($V=W^\pm,Z$) in the pole approximation. As is well known, the computation can be organised into factorisable and non-factorisable contributions. The factorisable corrections can be computed by evaluating the (polarised) EW form factor of the vector boson at the relevant perturbative order. The non-factorisable corrections are instead driven by soft-photon exchanges between the initial- and final-state fermions and/or the resonance. We perform an explicit two-loop computation to show that, once the heavy degrees of freedom are properly decoupled, such non-factorisable corrections can be expressed as an iteration of the one-loop result, plus a new contribution due to (light) fermion loops. The final two-loop result, which can be expected on general grounds from soft-photon factorisation, is shown to hold exactly in dimensional regularisation and is peculiar to the exchange of a single resonance. We discuss its extension to all perturbative orders.

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hep-ph 2026-05-11 2 theorems

Triangle singularities create narrow peaks near DK thresholds in Ds pi spectra

Probing the nature of D₁ K and D₂ K molecules through D_s^{(*)}ππ and D_{s0(s1)}π decays

Predicted signatures in Ds(*)ππ and Ds0(s1)π decays test the molecular nature of D1K and D2K states.

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We study the two- and three-body decays of the $I=0$ $D_1K$ and $D_2K$ molecular states $T_{c\bar{s}1}^*$ and $T_{c\bar{s}2}^*$ into $D_s^{(*)}$ mesons and pions. Triangle singularities produce narrow peaks in the $D_s^*\pi$ and $D_s\pi$ invariant mass spectra near the $D^*K$ and $DK$ thresholds. The isospin-violating two-body decays $T_{c\bar{s}1}^*\to D_{s1}(2460)\pi^0$, $T_{c\bar{s}2}^*\to D_{s1}(2460)\pi^0$, and $T_{c\bar{s}2}^*\to D_{s0}^*(2317)\pi^0$ exhibit large partial widths, reflecting the strong couplings inherent to molecular states. These predictions, obtained within heavy hadron chiral perturbation theory and the chiral unitary approach, provide complementary signatures for identifying $D_1K$ and $D_2K$ molecules at experiments.

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hep-ph 2026-05-11 2 theorems

Closed-form method reconstructs ortho-positronium decay vertex

Ortho-Positronium Three-Photon Decays: Physics Constraints and a Closed-Form Energy Method for Annihilation Vertex Reconstruction

Energy-momentum conservation produces a unique analytical solution from measured photon data

abstract click to expand

We examine the physical foundations of orthopositronium three-photon decay in the context of annihilation vertex reconstruction, focusing on how energy-momentum conservation constrains the space of physically admissible solutions. Finally, we provide a closed-form analytical derivation of an energy-based vertex reconstruction algorithm.

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hep-ph 2026-05-11 1 theorem

Massless scalar pair can exactly mimic Michel decay pattern

Can a Nonstandard Invisible Pair Mimic the Michel Distribution?

This nonstandard invisible sector reproduces all measurable distributions, including polarization and radiative channels.

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We ask whether a measured Michel distribution, apparently in excellent agreement with the Standard Model interpretation of the $\ell_i \to \ell_j \nu\bar\nu$ decay, could instead arise from a different invisible sector. Within a general low-energy effective field theory, we analyze lepton decays $\ell_i \to \ell_j + X\bar X$ for electrically neutral, color-singlet, mutually conjugate invisible pairs $X\bar X$ of spin up to $2$, allowing (pseudo)scalar, (axial)vector, and antisymmetric tensor interactions in the lepton current, focusing on the massless limit relevant for exact degeneracies. We formulate a criterion for indistinguishability based on the full set of measurable differential distributions. Under these assumptions, besides the obvious spin $1/2$ case, there is a unique nontrivial solution: a massless complex scalar pair coupled through a purely left-handed vector current exactly reproduces the standard Michel pattern, including its extensions to daughter-lepton polarization and radiative channels. All other cases studied here are distinguishable, in particular because higher-spin invisible pairs produce additional kinematic prefactors. These results isolate the only nonstandard and nontrivial invisible sector that can remain hidden in Michel-type lepton decay measurements.

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hep-ph 2026-05-11 Recognition

Physics-informed net infers unmeasured hadron spectra at LHC

Inferring identified hadron production in pp collisions with physics-informed machine learning at the LHC

Trained on PYTHIA8 with yield-ratio and smoothness constraints, it extrapolates pT spectra with under 6 percent uncertainty.

abstract click to expand

Machine learning has become a powerful tool in high-energy collider experiments, which enables the studies based on data-driven approaches to complex reconstruction and regression tasks. The study of identified hadron spectra in pseudorapidity regions beyond detector acceptance, which is limited to mid-rapidity regions, carries important information about particle production, yet remains unmeasured. In this work, we develop a physics-informed neural network, trained on PYTHIA8 $pp$ collisions at $\sqrt{s}=13.6$ TeV, to infer $p_{\rm T}$ spectra of $\pi^{\pm}$, $K^{\pm}$, $p/\bar{p}$, $\Lambda/\bar{\Lambda}$, and $K^{0}_{\mathrm{s}}$ in different rapidity regions. Physics-motivated constraints, including particle yield ratios, spectral shape, and smoothness, are incorporated into the loss function. A staged hyperparameter optimization strategy is used to ensure stability. The model achieves yield uncertainties of ${\sim}1.5\%$, $1.8\%$, and $5.83\%$ in the training, interpolation, and extrapolation regimes, respectively, outperforming XGBoost and LightGBM. It further reproduces key observables such as particle yield ratios, the multiplicity dependence of $\langle p_{\rm T} \rangle$, and kinetic freeze-out parameters, indicating that the model captures the underlying physics and provides reliable predictions beyond the measured phase space.

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hep-ph 2026-05-11 2 theorems

Optimizer tunes Yukawa couplings to suppress proton decay in SU(5) GUT

Optimizing Yukawa couplings to suppress Dimension-five Proton Decay in SU(5) GUT

Adam optimization over 33 Yukawa parameters yields proton lifetimes above the 5.9 x 10^33 year bound for multiple tan beta values.

abstract click to expand

The minimal supersymmetric $SU(5)$ grand unified theory (GUT) provides a highly compelling framework for physics beyond the Standard Model (SM). However, it suffers from a severe phenomenological challenge: rapid proton decay mediated by colored-Higgsino exchange via dimension-five operators. Resolving this issue often requires adjustments to the Yukawa couplings and the potential sectors, generating a vast and complex parameter space where traditional brute-force numerical scans are rendered computationally intractable due to the curse of dimensionality. In this paper, we overcome this limitation by applying machine learning optimization techniques. We investigate a supersymmetric $SU(5)$ model extended with $\mathbf{45}$ and $\overline{\mathbf{45}}$ Higgs representations, defining a loss function based on the partial decay width of $p \to K^+ \bar{\nu}$. Utilizing the Adam optimizer, we systematically explore the 33-dimensional parameter space to identify regions that suppress proton decay. Furthermore, we vary $\tan \beta$ to thoroughly investigate whether the optimized proton lifetime can consistently exceed the stringent experimental lower bound of $5.9 \times 10^{33}$ years established by the Super-Kamiokande collaboration.

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hep-ph 2026-05-11 1 theorem

Formulas give FL, FS and G straight from F2 at small x

Direct determination of the structure functions F_L, F_S and G from F₂ and dF₂/dQ² to O(α_s²)

The expressions work to consistent NNLO accuracy once non-singlet pieces are subtracted with known quark distributions.

abstract click to expand

We extend the results of Lappi {\em et al.}, Eur.~Phys.~J.~C {\bf 84}, 84 (2024), to show that it is possible to obtain expressions for the longitudinal, singlet and gluon structure functions $F_L$, $F_S$ and $G$ in deep inelastic scattering directly in terms of the measured functions $F_2$ and $dF_2/\ln(Q^2)$ {\em modulo} non-singlet corrections expected to be small at very small $x$. The latter can be treated at low $x$ using existing quark distributions. Our results are presented consistently to $O(\alpha_s^2)$, correcting and extending the mixed-order results of Lappi {\em et al.}.

1 0

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hep-ph 2026-05-11 Recognition

T-model geometry allows hybrid inflation without trajectory extrema

F-Term Hybrid Inflation with T-Model K\"ahler Geometry and Beyond

Broad parameter space matches ACT and SPT data while cosmic strings produce detectable gravitational waves.

abstract click to expand

We analyze F-term hybrid inflation (FHI) within various grand unified theories (GUTs) in the presence of a K\"ahler potential for the inflaton field which parameterizes the K\"ahler manifolds $SU(1,1)/U(1)$ or $SU(2)/U(1)$. We take into account supergravity, radiative, and soft supersymmetry-breaking corrections to the tree-level potential and find that viable FHI can be realized without extrema along the inflationary trajectory for a broad region of the parameter space. For selected superpotential parameters the models' predictions are largely influenced by the curvature of the internal space and the magnitude of the tadpole parameter which are constrained so as to achieve compatibility with the current ACT and SPT data. We also discuss the formation of cosmic strings and their associated gravitational wave signals, potentially detectable by current and upcoming experiments.

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hep-ph 2026-05-11 Recognition

Three leptoquarks explain B anomalies with tau-only couplings

B anomalies and the tauphilic leptoquark model

S1 fixes R(D*), ~R2 matches neutrino modes, S3 satisfies mixing with all masses under 3 TeV

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We suggest three scalar leptoquarks, $S_1$, ${\tilde R}_2$, and $S_3$ which couple exclusively to the 3rd generation of leptons to explain the $B$ anomalies. The scalar singlet $S_1$ can explain $R(D^{(*)})$, while the doublet ${\tilde R}_2$ is needed to fit the branching ratio ${\rm Br}(B\to K^{(*)}\nu{\bar\nu})$ via the right-handed Wilson coefficients $C_R^\nu$. A strong constraint from $\Delta m_{B_s}$ requires triplet $S_3$ where the mixing term between $S_1$ and $S_3$ is important. Our analysis suggests subdominant $C_{V_L}<0$ and dominant $C_{S_L} >0$ and lepton-flavor universality violating $C_9^{\rm LQ} \approx +1$. The masses are expected to be $M_{S_1}\sim M_{{\tilde R}_2} < M_{S_3} \lesssim 3$ TeV, which can be probed in future colliders.

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hep-ph 2026-05-11 2 theorems

Reciprocal symmetry implies local constraint on multiplicity derivatives

Higher-order local constraints from reciprocal symmetry and entanglement entropy of charged-particle multiplicity distributions in pp collisions

The k=1 relation among third and second derivatives holds near the mean in 13 TeV data, while global symmetry is rejected at high precision.

abstract click to expand

The reciprocal symmetry $f_s(z)=f_s(1/z)$ of the KNO-violating term in proton--proton charged-multiplicity distributions, observed at $\sqrt{s}=7$, $8$ and $13$ TeV, implies that the function $h(u)\equiv f_s(e^u)$ is even in $u=\ln z$. Each odd derivative of $h$ at $u=0$ then provides a local algebraic constraint on the multiplicity distribution at $n=\langle n\rangle$. The $k=0$ constraint $P'(\langle n\rangle)=-P(\langle n\rangle)/\langle n\rangle$ has been verified previously. We derive the $k=1$ constraint, $\langle n\rangle^3 P'''(\langle n\rangle)+6\langle n\rangle^2 P''(\langle n\rangle)=5\,P(\langle n\rangle)$, equivalent to the unconditional residual $\delta_3\equiv 1-2\rho_0+\rho_1=0$, and test it in the ATLAS data: at $13$~TeV with the largest fit window we find $\delta_3=-0.02\pm 0.11$, consistent with the leading-order symmetric value, while the $7$ and $8$~TeV results are inconclusive at the available precision. A $\chi^2$ test of the global symmetry across the window $1/3<z<3$ is consistent with the symmetry at $7$ and $8$~TeV but rejects it decisively at $13$~TeV, where the smaller experimental uncertainties expose a residual departure from $z\to 1/z$ invariance away from $z=1$. The overall picture is therefore that the symmetry holds at the leading two non-trivial orders near $z=1$ but breaks down globally at the precision afforded by the $13$~TeV data, suggesting that $f_s(z)=f_s(1/z)$ is at best an approximate symmetry. We derive a model-independent expression for the entanglement entropy $S=\ln\langle n\rangle+1-\tfrac{1}{2}\int_0^\infty e^{-z}f_s^2(z)\,dz+\mathcal{O}(f_s^3)$, in which the linear term in $f_s$ cancels by virtue of normalisation and the constraint $\langle z\rangle=1$, and evaluate it numerically on the ATLAS data.

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hep-ph 2026-05-11 Recognition

Net-baryon fluctuations follow mean-field scaling near the critical point

Scaling properties of net-baryon number fluctuations at the deconfinement critical point

In the heavy quark limit of QCD the critical region shrinks with baryon density and beyond-mean-field exponents are estimated from the 3D Is

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We investigate the critical behavior of the first four cumulants of the net-baryon number near the deconfinement critical point in QCD in the limit of heavy quarks. By connecting baryon-number fluctuations to Polyakov loop susceptibilities, we analyze their mean-field scaling properties at zero and non-zero baryon chemical potentials. In the mean-field approximation we derive critical exponents via the Landau theory and validate them through explicit numerical calculations in an effective Polyakov loop model. Using a Ginzburg-Landau criterion as a diagnostic of beyond-mean-field effects, we estimate the size of the critical region and find that it shrinks with increasing baryon density. By utilizing the exact scaling function in the 3D Ising model, we estimate critical exponents beyond the mean-field approximation.

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hep-ph 2026-05-11 Recognition

CLIC could limit LFV Higgs decays to 10^{-5}

Lepton Flavor Violating Higgs decays at the Compact Linear Collider

Projections show 95% CL upper limits of 10^{-4} to 10^{-5} on branching fractions with planned luminosities at 1.4 TeV and 3 TeV.

abstract click to expand

Lepton flavor violating Higgs decays could appear in scenarios beyond the Standard Model of particle physics. In this article, we study the sensitivity of a future Compact Linear Collider (CLIC) to such processes, namely, $h\rightarrow e\mu$, $h\rightarrow\tau\mu$, and $h\rightarrow e\tau$. In the absence of any observation, 95\% CL\ upper limits in the region of $10^{-4}$ to $10^{-5}$ could be placed on the branching fractions of these processes, assuming integrated luminosities of $4$\,ab$^{-1}$ at $\sqrt{s}=1.4$ TeV and $5$\,ab$^{-1}$ at $\sqrt{s}=3$ TeV.

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hep-ph 2026-05-11 Recognition

Entanglement entropy distinguishes neutrino mass hierarchy in matter

Tripartite Entanglement as a Probe of Neutrino Mass Hierarchy, CP Violation, and Non-Standard Interactions

The difference between normal and inverted orderings peaks at L/E of 655 km/GeV and stays linear with non-standard interaction strength.

abstract click to expand

We investigate global tripartite quantum entanglement in three-flavor neutrino oscillations as a tool for probing the neutrino mass hierarchy and CP violation. Using the linear entropy formalism, we compute the global entanglement entropy for an initial electron neutrino state as a function of L/E, comparing Normal Ordering (NO) and Inverted Ordering (IO) across CP phases 0, 90, 120 and 180, in vacuum and in constant-density matter rho = 2.8g/cm^3, L = 1300km). We define the hierarchy sensitivity diagnostic dell S and show that MSW matter effects amplify dell S by roughly a factor of two relative to vacuum, with peak sensitivity at L/E approx 655km/GeV (approx 2GeV at the DUNE baseline). For antineutrinos the diagnostic is near-perfectly antisymmetric to the neutrino case at the MSW resonance, with deviations directly encoding dell CP. ANnother diagonostic defined here separates the matter hierarchy signal from the CP asymmetry signal in the tripartite entanglement. For non-standard interactions (NSI) parameterized by epsilon_{ee}, we find Dell S{max} is approx 0.113 + 0.105epsilon_{ee}, a linear and CP-phase-independent relation. The optimal L/E for hierarchy discrimination is stable at approx 655km/GeV for all epsilon_{ee}less than or equal to 0.2, providing a robust, NSI-independent energy recommendation for DUNE.

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hep-ph 2026-05-11 Recognition

High-energy WZ and Wh ratios approach one in SMEFT

Electroweak Restoration: SMEFT and HEFT

The cross-section ratio of W_L Z_L to W_L h production tests linear versus non-linear electroweak symmetry at the HL-LHC.

abstract click to expand

Colliders continue to push our understanding of electroweak (EW) interactions to ever higher energies. At high energies, many observables in the broken EW theory are expected to approach the unbroken theory. This is the electroweak restoration regime, where longitudinal gauge boson production corresponds to Goldstone boson production. As such, in this paper we investigate electroweak restoration in the context of linear and non-linear realizations of the EW symmetry in longitudinal di-boson production: $f\bar{f}'\rightarrow V_LV'_L$ and $f\bar{f}'\rightarrow V_Lh$, where $V_L,V'_L$ are longitudinal gauge bosons, $h$ is the Higgs boson, and $f,f'$ are SM fermions. For the linear beyond the SM (BSM) theory, we use the Standard Model Effective Theory (SMEFT), and for the non-linear BSM theory, we use Higgs Effective Field Theory (HEFT). We give a general discussion of these amplitudes and cross sections in the SM, SMEFT, and HEFT. Using the Goldstone boson equivalence theorem, we derive a set of ratios among high energy $V_LV'_L$ and $V_Lh$ amplitudes that are expected to approach one in the SM and SMEFT. Through our explicit calculations, we show that these ratios do indeed approach one in the SM and dimension-6 SMEFT, but not necessarily HEFT. Beyond the amplitudes, both theoretically and experimentally, we identify the cross section ratio of $W^\pm_LZ_L$ and $W^\pm_L h$ as a particularly promising observable to probe EW restoration and distinguish HEFT and SMEFT. Using current LHC measurements as well as projections for $W^\pm_L h$ measurements, we project HL-LHC sensitivities to probing the linear vs. non-linear realizations of the EW symmetry.

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hep-ph 2026-05-11 Recognition

GAPS data may sharpen light DM annihilation limits by 10x

Revisiting predictions for cosmic-ray antinucleon fluxes from Galactic Dark Matter

Low-energy antiproton measurements complement AMS-02 to constrain candidates below 50 GeV under two propagation models.

abstract click to expand

The data on cosmic antiprotons have reached an outstanding precision on energies spanning from GeV to hundreds of TeV, thanks to the space-based AMS-02 experiment. The balloon-borne GAPS experiment, which just completed its first Antarctic flight, will address antiproton and antideuteron fluxes well below GeV energies. Antinuclei in cosmic rays, as well as being produced by spallation reactions between cosmic-ray nuclei and the atoms of the interstellar medium, may hide contributions from exotic sources, such as particle dark matter annihilation in the Galaxy. In this paper, we present predictions for cosmic antiproton, antideuteron and antihelium fluxes both from secondary and dark matter origin. We use state-of-the-art production spectra, nuclear coalescence for antinuclei, and Galactic propagation models to derive upper limits on the dark matter annihilation cross-section from AMS-02 antiproton data in different propagation scenarios (BIG and QUAINT). We quantify the impact of future GAPS data, showing that its sensitivity to sub-GV antiprotons could improve the $\langle\sigma v\rangle$ constraints by up to an order of magnitude for light DM ($m_{\chi} \lesssim 50$ GeV). For heavier antinuclei, the detection perspective with existing and upcoming experiments are derived for those scenarios consistent with AMS-02 antiproton flux. The detectability of such signals strongly depends on the experiment, the propagation model, and the hadronization tuning. Our analysis underscores the complementarity of antinuclei channels for indirect DM searches and the critical role of low-energy windows in constraining light DM candidates.

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hep-ph 2026-05-11 Recognition

Expansion makes primordial black hole hotspots disappear in finite time

Primordial Black Hole Hotspots Beyond Flat Spacetime

Plateau temperature cools as t to the -11/15 after an initial drop, steeper than the flat-spacetime t to the -7/15 scaling.

abstract click to expand

Light primordial black holes heat the surrounding plasma via Hawking radiation, forming localized hotspots whose temperature may far exceed that of the cosmological background. Previous studies of hotspot formation and cooling have treated the subsequent energy transport in flat spacetime, thereby neglecting the expansion of the Universe. We formulate the diffusion equation governing the hotspot evolution, in an expanding universe, and clarify the regime in which the formalism is valid. We find that hotspot formation is robust against cosmological expansion. We show that the critical distance scale, where Hubble expansion overtakes diffusion, coincides with the decoupling radius introduced in earlier work, and the temperature profile $T\propto r^{-7/11}$ essentially remains unchanged. However, the cooling stage is substantially modified. We find that the plateau temperature of a cooling hotspot initially undergoes a rapid drop and then follows $T_{\rm plt} \propto t^{-11/15}$, steeper than the flat-spacetime scaling $t^{-7/15}$. This scaling cannot be obtained by simply redshifting the flat-spacetime solution, because expansion also suppresses diffusive transport. As a consequence, all hotspots disappear within a finite time, as opposed to the flat-spacetime prediction of everlasting hotspots in part of the parameter space.

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hep-ph 2026-05-11 Recognition

Entanglement bounds how large coherent detector gains can grow

Entanglement Requirements for Coherent Enhancement in Detectors

New limits tie coherence scaling to single-mode entanglement entropy in both metrology and scattering experiments.

abstract click to expand

Coherent enhancement is a powerful mechanism for improving the sensitivity of a wide range of detectors, but its practical use is often limited by the difficulty of preparing the required quantum states. We show that this difficulty has a fundamental origin: coherent enhancement of a signal interacting with a detector is quantitatively constrained by entanglement. We prove general bounds on how the strength of coherent effects can scale with system size, as a function of the single-mode entanglement entropy of the detector. These bounds smoothly interpolate between the incoherent and fully coherent regimes, and apply both to parameter-estimation problems and to scattering processes. We discuss these results from two complementary perspectives: First, they appear as bounds on the quantum Fisher information of many-body states, which translate directly into limits on parameter sensitivity via the quantum Cram\'er-Rao bound. Second, they can be interpreted as limits on a class of scattering cross sections, leading to predictions for how minimum detectable interaction strengths scale with target size. Together, these results provide a unified view of coherent enhancement in metrology and scattering experiments, and motivate the development of new techniques for generating entangled detector states.

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hep-ph 2026-05-11 2 theorems

Cosmic ray scattering explains galactic center gamma excess

Producing the GeV Galactic Center Excess via Cosmic Ray-Dark Matter Scattering

Scattering of cosmic rays on dark matter particles matches the observed GeV spectrum in two model classes.

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In this work, we propose a novel mechanism for generating gamma rays from the Galactic Center via scattering of cosmic-ray protons off dark matter in the Milky Way halo, in contrast to conventional explanations based on dark matter annihilation. We present two examples of this framework that produce an observable photon signal. In the inelastic dark matter model, cosmic rays up-scatter a lighter dark matter particle, with the subsequent decay of the heavier particle yielding two photons. In the elastic dark matter model, an energetic photon is directly produced in the final state of a 2-to-3 scattering process. We show that, for a range of viable model parameters, this framework provides a fit to the observed Galactic Center gamma-ray excess spectrum comparable to those obtained from dark matter annihilation and millisecond pulsar models. Our results open a new avenue for interpreting gamma-ray observations of the Galactic Center.

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hep-ph 2026-05-11 Recognition

Perturbative corrections shift B decay observables by 3%

Symmetry-Breaking Effects on Form Factors and Observables in B to K₀^*(1430)μ^+μ^- Decay

Deviations in branching ratio or normal lepton asymmetry would indicate new physics

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In the heavy-quark and large-energy limits, symmetry relations reduce the number of independent form factors governing heavy-to-light $B$-meson decays. Exploiting these relations, the form factors can be parametrized while systematically incorporating symmetry-breaking corrections from perturbative QCD. Using vertex renormalization together with light-cone distribution amplitudes, we compute the vertex and hard-spectator contributions for the $B \to K_0^*(1430)$ transition. We then analyze the impact of these form factors on physical observables, including the branching ratio and lepton polarization asymmetries $(P_L, P_N)$, in $B \to K_0^*(1430)\mu^+\mu^-$. Our results indicate that perturbative corrections induce modest shifts of $\sim 3\%$ in both the branching ratio and the normal lepton polarization asymmetry. Consequently, any significant deviation observed experimentally from these predictions would provide a clear signal of potential New Physics effects.

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hep-ph 2026-05-11 2 theorems

Germanium CEνNS data tightens weak mixing angle and neutron radius

Phenomenological implications of the high-precision COHERENT germanium CEνNS data

High-precision COHERENT measurements combined with reactor data update Standard Model parameters and nuclear structure details.

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This work presents the first comprehensive phenomenological analysis of the newly released Coherent Elastic Neutrino-Nucleus Scattering (CE$\nu$NS) data on germanium, measured by the COHERENT collaboration at the Spallation Neutron Source. Leveraging the unprecedented precision of this dataset, we provide state-of-the-art determinations of key Standard Model and nuclear physics parameters. Specifically, we extract updated constraints on the weak mixing angle, the neutrino charge radii, and we perform a detailed extraction of the neutron root-mean-square radius of germanium nuclei. Additionally, we use these results to evaluate scenarios beyond the Standard Model, placing robust bounds on neutrino non-standard interactions. To maximize the statistical power and robustness of our findings, whenever possible, we perform a global combined analysis incorporating previous COHERENT measurements along with reactor antineutrino data from the CONUS+, TEXONO, and $\nu$GeN experiments as well as dark-matter experiments.

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hep-ph 2026-05-11 2 theorems

DUNE positioned to detect small departures from three-flavor neutrino mixing

Flavor as an Incomplete Structure: Conceptual Questions and the Role of DUNE

Long-baseline and near-detector complementarity plus PRISM data-driven predictions enable tests of the minimal framework.

abstract click to expand

Flavor remains one of the most successful yet least understood structures of the Standard Model. The discovery of the Higgs boson completed the electroweak account of mass generation, but did not explain the origin of fermion families, mass hierarchies, or mixing patterns. In this sense, flavor can be regarded as an empirically successful but conceptually incomplete structure. Neutrinos occupy a particularly sensitive place within this problem: their masses are tiny, their mixing is large, and their mass-generation mechanism may differ from that of charged fermions. In this article, we discuss flavor as an open conceptual problem and argue that DUNE, as a phased program spanning precision oscillation measurements and sensitivity to BSM and dark-sector phenomena, provides a powerful framework for testing the self-consistency and possible limits of the present three-flavor description. In particular, the complementarity between the long-baseline program and the Phase I near-detector complex, together with the DUNE-PRISM strategy for controlling interaction-model systematics and enabling data-driven near-to-far predictions, makes DUNE especially well-suited to search for small, correlated departures from the minimal flavor framework.

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hep-ph 2026-05-11 Recognition

DUNE to test if three-flavor neutrino picture is complete

Flavor as an Incomplete Structure: Conceptual Questions and the Role of DUNE

Precision oscillation data combined with near-detector measurements can reveal small correlated departures from the minimal model.

abstract click to expand

Flavor remains one of the most successful yet least understood structures of the Standard Model. The discovery of the Higgs boson completed the electroweak account of mass generation, but did not explain the origin of fermion families, mass hierarchies, or mixing patterns. In this sense, flavor can be regarded as an empirically successful but conceptually incomplete structure. Neutrinos occupy a particularly sensitive place within this problem: their masses are tiny, their mixing is large, and their mass-generation mechanism may differ from that of charged fermions. In this article, we discuss flavor as an open conceptual problem and argue that DUNE, as a phased program spanning precision oscillation measurements and sensitivity to BSM and dark-sector phenomena, provides a powerful framework for testing the self-consistency and possible limits of the present three-flavor description. In particular, the complementarity between the long-baseline program and the Phase I near-detector complex, together with the DUNE-PRISM strategy for controlling interaction-model systematics and enabling data-driven near-to-far predictions, makes DUNE especially well-suited to search for small, correlated departures from the minimal flavor framework.

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hep-ph 2026-05-11 2 theorems

Pair creation alone drives current along magnetic field in plasma

Pair creation as a source of longitudinal chiral magnetoconductivity

Real electron-positron pairs from photon absorption generate axial imbalance and longitudinal conductivity without external chirality input.

abstract click to expand

We demonstrate that chiral transport in a strongly magnetized electron-positron plasma can arise dynamically from dissipative pair-creation processes encoded in the imaginary part of the photon polarization tensor within one-loop finite-temperature quantum electrodynamics (QED). In the kinematic region corresponding to longitudinal photon absorption, real electron-positron pair production induces axial charge nonconservation and generates an electric current parallel to the magnetic field, without requiring the introduction of an external chiral chemical potential. This provides a microscopic mechanism for chiral magnetic transport, offering an alternative to hydrodynamic or anomaly-based effective descriptions in which chirality imbalance is typically introduced as an external input. We derive an explicit expression for the longitudinal magnetoconductivity associated with this process and show that it exhibits an approximately quadratic dependence on the magnetic field only within a restricted intermediate regime. This behavior emerges from the dominance of the lowest Landau levels as a characteristic of negative longitudinal magnetoresistance. We further analyze how Pauli blocking regulates the pair-creation phase-space and demonstrate that the dynamically generated chiral imbalance is suppressed at high frequencies, revealing a transition between chiral-active and non-chiral-active regimes. Our results connect microscopic QED processes with anomaly-related transport phenomena in strongly magnetized relativistic plasmas, where pair creation provides a dynamical source for chiral imbalance.

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hep-ph 2026-05-11 Recognition

Orbit space geometry fixes boundedness for Δ(54) three-Higgs potential

Conditions for boundedness from below of a Delta(54)-symmetric three-Higgs-doublet model

Shape of allowed field directions determines when the quartic potential stays positive at large scales.

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We investigate the orbit space of the scalar potential of a $\Delta(54)$-symmetric three-Higgs-doublet model. We find that, if the potential enjoys $CP$ invariance, then its three-dimensional orbit space is a polytope; if the potential has no $CP$ symmetry, then its four-dimensional orbit space has a boundary that is sometimes slightly concave, but seems never to be convex. Consequently, we conjecture necessary and sufficient conditions for the potential to be bounded from below; brute-force minimization of a large number of potentials affirms the accuracy of our conjecture. We list all possible charge-conserving and charge-breaking minima of the potential.

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hep-ph 2026-05-11 2 theorems

Charm mass fixed at 1275.8 MeV via scale-independent QCD sum rules

New Determinations of the Charm and Bottom Quark Masses Using QCD Quarkonium Sum Rules

PMC with characteristic operators removes renormalization dependence, yielding bottom mass 4177 MeV consistent with world data

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We reanalyze the perturbative QCD (pQCD) corrections to quarkonium QCD sum rules and extract the heavy quark masses $\overline{m}_{q}(\overline{m}_{q})$ ($q=c,b$). At present, the pQCD corrections to the correlation functions of two heavy-quark pseudoscalar and vector currents at zero momentum transfer, denoted as $M_{n,q}^{X,\rm th}$ ($X = P, V$), are calculated up to the $\mathcal{O}(\alpha_s^3)$ order. These corrections exhibit significant renormalization scheme and scale dependence, which introduces large theoretical uncertainties and deteriorates the precision of heavy quark mass determinations. In this work, we eliminate the renormalization scheme and scale ambiguities in the perturbative part of $M_{n,q}^{X,\rm th}$ by adopting the Principle of Maximum Conformality (PMC) within the characteristic operator (CO) approach. The CO approach, a novel extension of the standard PMC procedure, simultaneously determines the effective coupling $\alpha_s(Q_*)$ and the effective quark mass $\overline{m}_q(Q_*)$. It systematically absorbs the nonconformal $\{\beta_i\}$-terms and $\{\gamma_i\}$-terms via the renormalization group equations, yielding a strictly scheme- and scale-independent conformal perturbative series. Based on the improved PMC conformal series, we further provide reliable estimates for the unknown $\mathrm{N^4LO}$ contributions using the Pad\'e approximation method. The final predicted heavy quark masses in the $\overline{\mathrm{MS}}$ scheme read: $\overline{m}_c(\overline{m}_c)=1275.8\pm 0.4~\text{MeV}$, extracted from the second moment of the charmed pseudoscalar correlator $M_{2,c}^{P}$; and $\overline{m}_b(\overline{m}_b) = 4177.0 \pm 7.2~\text{MeV}$, extracted from the first moment of the bottom vector correlator $M_{1,b}^{V}$. Both results agree well with the PDG world averages with deviations smaller than $1\sigma$.

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hep-ph 2026-05-11 2 theorems

Black hole mini-spikes constrain Inert Doublet dark matter to multi-TeV

Probing the Inert Doublet Dark Matter with Stellar-Mass Black Hole Mini-Spikes

Fermi LAT observations of compressed dark matter around stellar black holes limit substantial regions of the model parameter space.

abstract click to expand

The nature of dark matter remains a central unresolved problem in contemporary physics, motivating the exploration of well-defined extensions of the Standard Model. Among these, the Inert Doublet Model provides a minimal and theoretically consistent framework accommodating a viable weakly interacting massive particle dark matter candidate. In this work, we investigate the IDM parameter space through an analysis of FermiLAT observations of dark matter mini-spikes surrounding stellar-mass black holes. Owing to the strong gravitational compression of dark matter in the vicinity of these systems, the resulting annihilation signal can be significantly enhanced, rendering such environments exceptionally sensitive probes of dark matter interactions. We find that substantial regions of the IDM parameter space, particularly in the high-mass regime, are subject to stringent constraints extending into the multi-TeV range. These results underscore the increasingly important role of indirect detection in probing particle dark matter scenarios beyond the reach of current collider and direct detection experiments.

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hep-ph 2026-05-11 2 theorems

LHC light-ion data indicates QGP in small systems

Light-Ion Collisions: Bridging Small and Large QCD Systems

First pO, OO and NeNe results connect proton-proton and heavy-ion regimes through observed collective flow.

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Light-ion collisions at the LHC bridge the gap between small proton-proton and large heavy-ion collision systems, providing a unique laboratory to study the onset of QCD collective phenomena. The first light-ion run at the LHC took place July~1--9, 2025, with proton-oxygen (pO), oxygen-oxygen (OO), and neon-neon (NeNe) collisions. Early experimental results provide strong evidence of quark-gluon plasma (QGP) formation in these small systems. I review the motivation for the light-ion collisions and the first experimental results, connecting perturbative QCD, hot QCD, and low-energy nuclear structure physics.

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hep-ph 2026-05-11 Recognition

AMPT without hadronic phase still matches K*0/K data

The study of K^{*0} meson production using a multi-phase transport model at RHIC BES energies

The result questions whether rescattering in the late hadronic stage is the main reason for the suppressed K*0 yield in central collisions.

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We present the yield, average transverse momentum, and collective flow measurement of $K^{*0}$ resonances in Au+Au collisions at $\sqrt{s_{NN}} = 19.6$, 14.5, and 7.7~GeV using the AMPT model. It is found that, due to hadronic rescattering, the decay daughters of $K^{*0}$ interact with other particles in the medium, causing the yield of reconstructable $K^{*0}$ to be significantly suppressed, especially at low transverse momentum. The model results are compared with recent experimental data from Phase-II of the Beam Energy Scan (BES-II) program at the Relativistic Heavy-Ion Collider. The string-melting version of the AMPT model successfully reproduces the measured $K^{*0}/K$ ratios at all three analysed collision energies. Interestingly, AMPT calculations that exclude the hadronic phase nevertheless provide a reasonable description of the data, thereby challenging the conventional interpretation that hadronic rescattering is the primary mechanism responsible for suppressing the $K^{*0}/K$ ratio in central heavy-ion collisions. In addition, we find that the $K^{*0}/K$ ratio appears to be largely insensitive to the lifetime of the hadronic phase, whereas the average transverse momentum, $\langle p_{T} \rangle$, of the $K^{*0}$ shows a strong dependence, increasing significantly as the lifetime of the hadronic phase becomes longer. We further show that the directed flow ($v_1$) of $K^{*0}$ mesons is strongly influenced by hadronic rescattering, whereas the elliptic flow ($v_2$) exhibits only weak sensitivity to hadronic effects. These results establish $K^{*0}$ directed flow as a sensitive probe of the late-stage hadronic medium in heavy-ion collisions. These model calculations therefore provide valuable insight into the underlying physics governing the observed experimental results at RHIC.

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