Explicit coupled-channel dynamics modifies pole structures and can eliminate or shift higher-lying states in doubly heavy systems, while single-channel models suffice only for near-threshold states like T_cc.
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Multiquark Resonances
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abstract
Multiquark resonances are undoubtedly experimentally observed. The number of states and the amount of details on their properties has been growing over the years. It is very recent the discovery of two pentaquarks and the confirmation of four tetraquarks, two of which had not been observed before. We mainly review the theoretical understanding of this sector of particle physics phenomenology and present some considerations attempting a coherent description of the so called X and Z resonances. The prominent problems plaguing theoretical models, like the absence of selection rules limiting the number of states predicted, motivate new directions in model building. Data are reviewed going through all of the observed resonances with particular attention to their common features and the purpose of providing a starting point to further research.
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A model-independent minimum in short-range production rates of dimer-spectator systems allows precise mass extraction for near-threshold states via a fixed relation to the observed dip position.
Chiral symmetry corrections in lattice QCD fits shift the D0*(2300) resonance pole closer to the Dπ threshold and reduce its width, while coupled channels produce a two-pole structure.
LCSR analysis of compact pentaquarks yields μ_u/μ_d = -2 for all currents and μ_c = 0 for one current, with numerical moments of order 1-3 μ_N that differ in flavor decomposition from molecular calculations.
QCD light-cone sum rules computation of magnetic dipole, electric quadrupole, and magnetic octupole moments for Σ-type P_ψs pentaquarks, with quark-flavor decomposition and model discriminants.
χ_c1(3872) is treated as a bound state in adjoint-meson Born-Oppenheimer potentials within a diabatic model, with calculated spin splittings and decay widths for its multiplet and bottom analogs after tuning to threshold.
Extends baryo-charmonium picture to c cbar ssq pentaquarks, predicting two negative-parity triplets with lowest kaon-associated state near 4.60 GeV and a near-degenerate doublet for upper kaon states.
A coupled-channel framework is developed and fitted to BESIII data on vector charmonium-like states in the 4.1-4.6 GeV range, concluding that coupled-channel effects with dynamically generated poles explain the line shapes.
The u-channel Lambda_c exchange enhances rescattering via Dbar(*) Sigma_c states in the piN to J/psiN reaction, producing clear peaks for Pc(4312) (1/2^-) and Pc(4457) (3/2^-) at microbarn cross sections while suppressing other states.
The authors compute mass spectra, rearrangement decays, and Regge trajectories for cs s-bar s-bar tetraquarks modeled as axial [cs][s-bar s-bar] systems in a Cornell potential framework with Ds threshold inputs.
A quark-diquark formalism extracts effective masses and couplings from known heavy baryon data to predict spectra across singly, doubly, and triply heavy sectors with two scenarios and a mass-dependent binding term.
Leading-order predictions for three-body point production rates of B and B* meson systems are derived in short-range NREFT from two-body input alone.
Joint analysis of experimental and lattice data confirms Z_c(3900) and Z_cs(3985) as SU(3) flavor partners with pole masses (3879.6 ± 4.8) MeV and (3976.9 ± 5.1) MeV, half-widths (32.2 ± 4.7) MeV and (28.8 ± 5.9) MeV, both resonances.
The DDK system supports a deeply bound compact state across wide parameters and possibly a shallow three-body halo state near the D-DK threshold, with negligible D*D*K coupling and no resonances.
The K D_s0*(2317) system develops a narrow resonance 40 MeV below threshold under the fixed-center molecular assumption, producing a characteristic correlation function for strong attraction.
Coupled-channel calculations show Pc and Pcs states as molecular bound states with RMS radii 0.5-2 fm when heavy-quark spin symmetry is respected across all channels.
QCD sum rule analysis predicts the mass of a J^P=0^- compact hidden-charm hexaquark to be 3.94-4.41 GeV.
Simulations indicate that heavy-ion collisions enhance the visibility of charmed-meson femtoscopic correlations compared to pp collisions, providing a probe for exotic hadronic states.
Machine learning models trained on known hadron data and an extended Gürsey-Radicati mass formula predict masses for triply heavy baryons and numerous pentaquark states, agreeing with available data and forecasting unobserved states.
The DNN system forms a robust compact bound state in the I=1/2 (1^-) channel across cutoffs, while D*NN exhibits spin-dependent bound states in 0^-, 1^-, and 2^- channels with no resonances found.
Fits using coupled channels and bare states show the psi(4660) as a conventional charmonium state above the Lambda_c pair threshold in both Belle and BESIII datasets.
QCD sum rules with local meson-meson currents for the K(1690) consistently predict masses around 2 GeV or above, disfavoring a molecular interpretation in favor of a compact multiquark state.
Develops uncertainty-aware fragmentation functions PQ5Q1.1 for all-charm pentaquarks using multimodal perturbative and nonperturbative modeling for collider predictions.
A review summarizing experimental contributions from BABAR, Belle, BESIII, and CLEO-c to the study of hadron production in open-charm meson pairs and insights into nonstandard hadrons.
citing papers explorer
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Systematic Study of Coupled-Channel Dynamics in Doubly Heavy Hadronic Molecules
Explicit coupled-channel dynamics modifies pole structures and can eliminate or shift higher-lying states in doubly heavy systems, while single-channel models suffice only for near-threshold states like T_cc.
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Model-independent mass determination of near-threshold states from short-range production
A model-independent minimum in short-range production rates of dimer-spectator systems allows precise mass extraction for near-threshold states via a fixed relation to the observed dip position.
-
Analysis of the $D_0^*(2300)$ resonance from lattice QCD under chiral symmetry
Chiral symmetry corrections in lattice QCD fits shift the D0*(2300) resonance pole closer to the Dπ threshold and reduce its width, while coupled channels produce a two-pole structure.
-
Analytic electromagnetic signatures of compact pentaquark structure: A multi-current QCD light-cone sum rules analysis of the $P_{\psi s}^{\Lambda}$ states
LCSR analysis of compact pentaquarks yields μ_u/μ_d = -2 for all currents and μ_c = 0 for one current, with numerical moments of order 1-3 μ_N that differ in flavor decomposition from molecular calculations.
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Deciphering the nature of $P^{\Sigma}_{\psi s}$ pentaquarks in the light of their electromagnetic multipole moments
QCD light-cone sum rules computation of magnetic dipole, electric quadrupole, and magnetic octupole moments for Σ-type P_ψs pentaquarks, with quark-flavor decomposition and model discriminants.
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$\boldsymbol{\chi_{c1}}(3872)$ and its Partners in the Diabatic Born-Oppenheimer Approximation for QCD
χ_c1(3872) is treated as a bound state in adjoint-meson Born-Oppenheimer potentials within a diabatic model, with calculated spin splittings and decay widths for its multiplet and bottom analogs after tuning to threshold.
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Doubly-strange hidden-charm pentaquarks from the Fermi statistics of the light-quark cloud
Extends baryo-charmonium picture to c cbar ssq pentaquarks, predicting two negative-parity triplets with lowest kaon-associated state near 4.60 GeV and a near-degenerate doublet for upper kaon states.
-
Vector charmonium(-like) states in the energy range of 4.1-4.6 GeV
A coupled-channel framework is developed and fitted to BESIII data on vector charmonium-like states in the 4.1-4.6 GeV range, concluding that coupled-channel effects with dynamically generated poles explain the line shapes.
-
Probing hidden-charm pentaquarks from the $\pi N\rightarrow J/\psi N$ reaction
The u-channel Lambda_c exchange enhances rescattering via Dbar(*) Sigma_c states in the piN to J/psiN reaction, producing clear peaks for Pc(4312) (1/2^-) and Pc(4457) (3/2^-) at microbarn cross sections while suppressing other states.
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Compact $cs\bar{s}\bar{s}$ Tetraquarks in the Charm--Strange Sector: Mass Spectra, Rearrangement Decays and Regge Trajectories with $D_s$ Threshold Inputs
The authors compute mass spectra, rearrangement decays, and Regge trajectories for cs s-bar s-bar tetraquarks modeled as axial [cs][s-bar s-bar] systems in a Cornell potential framework with Ds threshold inputs.
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Quark-diquark effective mass formalism for heavy baryon spectroscopy
A quark-diquark formalism extracts effective masses and couplings from known heavy baryon data to predict spectra across singly, doubly, and triply heavy sectors with two scenarios and a mass-dependent binding term.
-
Short-range production of three bottom mesons
Leading-order predictions for three-body point production rates of B and B* meson systems are derived in short-range NREFT from two-body input alone.
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Determination of the $Z_c(3900)$ and the $Z_{cs}(3985)$ states from joint analysis of experimental and lattice data
Joint analysis of experimental and lattice data confirms Z_c(3900) and Z_cs(3985) as SU(3) flavor partners with pole masses (3879.6 ± 4.8) MeV and (3976.9 ± 5.1) MeV, half-widths (32.2 ± 4.7) MeV and (28.8 ± 5.9) MeV, both resonances.
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Coupled-channel study of the three-body $DDK$ and $D^{*}D^{*}K$
The DDK system supports a deeply bound compact state across wide parameters and possibly a shallow three-body halo state near the D-DK threshold, with negligible D*D*K coupling and no resonances.
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Correlation function and bound state from the $K D_{s0}^*(2317)$ interaction
The K D_s0*(2317) system develops a narrow resonance 40 MeV below threshold under the fixed-center molecular assumption, producing a characteristic correlation function for strong attraction.
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Study of the molecular Properties of the $P_c$ and $P_{cs}$ States
Coupled-channel calculations show Pc and Pcs states as molecular bound states with RMS radii 0.5-2 fm when heavy-quark spin symmetry is respected across all channels.
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QCD Sum Rule Analysis of a Compact $D^{+}D^{-}K^{+}$-Like Hidden-Charm Hexaquark with $J^{P}=0^{-}$
QCD sum rule analysis predicts the mass of a J^P=0^- compact hidden-charm hexaquark to be 3.94-4.41 GeV.
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Accessing Exotic Hadronic States via Charmed-Meson Femtoscopy in Relativistic Heavy-Ion Collisions
Simulations indicate that heavy-ion collisions enhance the visibility of charmed-meson femtoscopic correlations compared to pp collisions, providing a probe for exotic hadronic states.
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Comprehensive Mass Predictions: From Triply Heavy Baryons to Pentaquarks
Machine learning models trained on known hadron data and an extended Gürsey-Radicati mass formula predict masses for triply heavy baryons and numerous pentaquark states, agreeing with available data and forecasting unobserved states.
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Three-body molecular states composed of $D^{(*)}$ and two nucleons
The DNN system forms a robust compact bound state in the I=1/2 (1^-) channel across cutoffs, while D*NN exhibits spin-dependent bound states in 0^-, 1^-, and 2^- channels with no resonances found.
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Does $\psi(4660)$ exist?
Fits using coupled channels and bare states show the psi(4660) as a conventional charmonium state above the Lambda_c pair threshold in both Belle and BESIII datasets.
-
QCD sum rule analysis of local meson-meson currents for the $K(1690)$ state
QCD sum rules with local meson-meson currents for the K(1690) consistently predict masses around 2 GeV or above, disfavoring a molecular interpretation in favor of a compact multiquark state.
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Multimodal Fragmentation of All-Heavy Pentaquarks: Uncertainty-Aware Predictions for Hadron Colliders
Develops uncertainty-aware fragmentation functions PQ5Q1.1 for all-charm pentaquarks using multimodal perturbative and nonperturbative modeling for collider predictions.
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Colloquium: Hadron Production in Open-charm Meson Pair at $e^+e^-$ Collider
A review summarizing experimental contributions from BABAR, Belle, BESIII, and CLEO-c to the study of hadron production in open-charm meson pairs and insights into nonstandard hadrons.
- All-charm tetraquarks at hadron colliders: A high-precision fragmentation perspective