REVIEW 5 minor 2 cited by
BESIII's complex scalar fix for the D o Kµ u q^{2} anomaly is ruled out by LHC high-pT data; only tiny real-coupling pairs survive.
Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →
T0 review · grok-4.5
2026-07-13 17:57 UTC pith:45MHW4SI
load-bearing objection Clean, useful letter that kills the BESIII complex-g_S fix with published LHC data and maps the remaining tiny real two-coupling windows.
Interpreting the results on exclusive crightarrow sμν modes
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The complex scalar coupling g_S proposed by BESIII to accommodate the q^{2}-binned D o Kµν data is in almost 2σ tension with the LHC high-pT bound |g_S|<0.014 (95 % CL). Several pairs of real-valued LEFT couplings remain compatible with both the low-energy measurements and the LHC mono-lepton plus Wh constraints, but the allowed values are too small to produce observable shifts in any integrated branching fraction or asymmetry.
What carries the argument
The tree-level SMEFT–LEFT matching of the five charged-current operators (g_VL, g_VR, g_SL, g_SR, g_T) together with three-loop QCD running to 2 GeV, combined with energy-enhanced high-pT tails of pp oµν and pp o Wh that constrain the same Wilson coefficients.
Load-bearing premise
The quantitative exclusion of complex g_S (and the size of the remaining real-coupling windows) rests on the HighPT implementation of ATLAS mono-lepton data and on the tree-level matching plus running of the scalar operators; any under-estimate of higher-order or PDF uncertainties in those high-pT tails would reopen the complex-scalar window.
What would settle it
A re-analysis of the ATLAS high-pT mono-lepton spectrum that relaxes the bound |g_S|<0.014 enough to re-admit the BESIII complex-g_S region, or a first measurement of the q^{2}-binned angular coefficients of Ds oϕµν that shows O(10 %) deviations at large q^{2} consistent with one of the allowed real two-coupling scenarios.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper re-examines the recent BESIII q^{2}-binned measurements of the D o Kµν rate and forward-backward asymmetry, which show a mild (~2σ) cumulative deviation from the SM. Using three independent LQCD form-factor sets (ETMC, FNAL/MILC, HPQCD) and the published BESIII correlations, the authors confirm that the discrepancy is driven by the high-q^{2} bins of the differential rate. They demonstrate that the complex scalar coupling g_S proposed by BESIII is incompatible (nearly 2σ) with the LHC high-p_T mono-lepton bound |g_S|<0.014 (95% CL). Restricting to real couplings, they map the two-dimensional planes allowed by the combination of D o Kµν, D_s oµν and LHC (mono-lepton + Wh) constraints; the surviving windows are too small to affect integrated observables but could produce O(10%) effects in the high-q^{2} angular coefficients of D_s oϕµν or Λ_c oΛµν. HL-LHC projections are also shown.
Significance. The work cleanly closes a proposed BSM explanation of a timely experimental anomaly by confronting it with independent high-energy data, while systematically charting the remaining real-coupling scenarios. Strengths include the use of three independent LQCD form-factor determinations, the published BESIII correlation matrices, the HighPT implementation of ATLAS mono-lepton data, and the complementary Wh STXS constraints that isolate right-handed vector currents. The resulting 2σ contours in Fig. 5 are genuine intersections of external inputs and furnish concrete, falsifiable targets for future angular analyses. The paper therefore supplies a useful, model-independent reference for both low-energy and collider communities working on charged-current charm decays.
minor comments (5)
- In Sec. II the angular convention difference with BESIII is noted only in a footnote; a short explicit statement in the main text (or in the caption of Fig. 1) would help readers avoid sign confusion when comparing A_fb.
- Eqs. (18)–(19) quote the three-loop QCD running factors without citing the precise numerical source or the residual scale uncertainty; a one-sentence remark on the size of that uncertainty would strengthen the discussion of the complex-g_S exclusion.
- Fig. 5 panels would be clearer if the black 2σ contour were drawn with a thicker line or a distinct colour, and if the HL-LHC projection (dashed) were labelled in the legend rather than only in the caption.
- The statement that D o K*µν is omitted because of the lack of reliable LQCD form factors is correct, but a brief pointer to the most recent (even if incomplete) lattice efforts would be useful for completeness.
- Typographical: “compleX g_S” in the section heading of Sec. III and a few missing spaces around “q^{2}-binned” appear in the arXiv version; these are easily fixed.
Circularity Check
No circularity: low-energy BESIII+LQCD constraints and high-pT LHC bounds are independent external inputs whose intersection is reported, not constructed.
full rationale
The paper takes published BESIII q^{2}-binned rates and A_fb (with correlations), three independent LQCD form-factor sets, the PDG Ds oµν branching fraction and FLAG f_Ds, and ATLAS mono-lepton plus Wh STXS data (via HighPT and the matching/running formulae of the literature). It computes χ^{2} surfaces and overlays the resulting 2σ regions; the black contours of Fig. 5 are simply the intersections of these independent data sets. No parameter is fitted to one observable and then re-used as a “prediction” of a related observable; no uniqueness theorem is imported from the authors’ prior work to force the operator basis; the SMEFT matching (Eqs. 17–19) and three-loop QCD running are standard external results. Self-citations ([3,4,6,14]) supply analysis tools and earlier related calculations but are not load-bearing for the central claim that complex g_S is already excluded while real two-coupling windows remain tiny. The derivation is therefore self-contained against external benchmarks.
Axiom & Free-Parameter Ledger
free parameters (1)
- g_VL, g_VR, g_SL, g_SR, g_T (real or complex)
axioms (4)
- domain assumption Dimension-6 LEFT Lagrangian (Eq. 1) with only left-handed neutrinos captures all relevant NP effects below the electroweak scale.
- domain assumption Tree-level SMEFT matching (Eqs. 17) plus three-loop QCD + one-loop QED running (Eqs. 18–19) correctly relates high-scale coefficients to the low-energy g_J at µ=2 GeV.
- domain assumption LQCD form factors of ETMC, FNAL/MILC and HPQCD (and f_Ds from FLAG) are accurate within the quoted uncertainties.
- domain assumption HighPT implementation of ATLAS mono-lepton and Wh STXS data correctly encodes the energy-enhanced contributions of the ψ⁴ and ψ²DH² operators.
read the original abstract
We examine the $q^2$-binned distributions of the $D\to K\mu\nu$ decay rate and of the corresponding forward-backward asymmetry which were recently measured by BESIII, showing a mild deviation from the Standard Model predictions. We point out that the proposed solution to remedy the discrepancy by turning on a complex-valued New Physics coupling is in tension with the constraints deduced from the LHC bounds on the high-$p_T$ tail of the relevant Drell-Yan process. We then show that there are several plausible scenarios that are compatible with both the measured low-energy and high-energy constraints but the selected couplings appear to be too small to be observed in the measurements of integrated observables, except for possibly the $q^2$-binned distribution of the angular observables relevant to $D_s\to \phi (\to KK) \mu\nu$ or $\Lambda_c\to \Lambda (\to p \pi) \mu\nu$ modes.
Forward citations
Cited by 2 Pith papers
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Scalar and Tensor Form Factors for $\Lambda \rightarrow p\ell \bar{\nu}_\ell$ from Lattice QCD
Lattice QCD yields the scalar and tensor form factors for Λ→pℓν̄ℓ as functions of q², providing a model-independent input to constrain non-standard charged-current interactions via the predicted R^{μe} ratio compared ...
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Hunting for new physics in $B$ meson $b \to u$ transitions: A fresh look with Belle II data
Combined Belle II analysis of b→uℓν modes favors Re(ε_μ^{2})≠0 at 2σ while yielding |V_ub|=(3.79±0.17)×10^{-3} in a global NP fit.
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Mono-lepton Drell-Yan processes which directly probe theψ 4 operators inducing charged-current interactions. At the parton level, these operators induce [3, 5]: ˆσ ui ¯dj →ℓν ˆσ ui ¯dj →ℓν SM = 1 +g ij(H) VL − ˆs m2 W gijℓ(ψ) VL 2 + gij(H) VR 2 + ˆs2 m4 W 3 4 |gij ℓ SR |2 +|g ij ℓ SL |2 + 4|gij ℓ T |2 , (20) where we have taken the limit ˆs≫m 2 W and con-...
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Higgs +Wboson production allows to directly con- strain the Higgs-current operators. These opera- tors induce an energy enhancement to the cross- section as [6] ˆσ(ui ¯dj →W h) ˆσ(ui ¯dj →W h) SM = 1 + gij(H) VL ˆs m2 W 2 + gij(H) VR ˆs m2 W 2 ,(22) where only the energy-enhanced contributions from d= 6 operators have been kept in the limit ˆs≫ m2 W . Con...
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