Radiative decays of J/ψ, ψ(2S)→γη(′) in perturbative QCD with relativistic corrections
Abstract
We present the first calculation of the radiative decays J/ψ,ψ(2S)→γη(′) in perturbative QCD that includes the order-q2 relativistic corrections in all three short-distance contributions, namely the quark-antiquark, two-gluon, and QED contributions. The amplitudes are found to be remarkably insensitive to the light-cone distribution amplitude and to the light-quark mass, a robustness that persists through order q2 and makes the predictions correspondingly reliable. The relativistic correction enhances the J/ψ branching ratios by roughly a factor of 2, narrowing their shortfall from experiment, whereas for the ψ(2S) it is about twice as large as for the J/ψ and the low-order expansion converges poorly. In two representative η--η′ mixing schemes, the ratio ℛ1S=ℬ(γη′)/ℬ(γη) proves sharply sensitive to the mixing angle and favors the smaller of the two. The predicted ψ(2S) rates lie well above the data in both channels, already at leading order, and most severely for the anomalously small γη channel. Such a discrepancy suggests that a mechanism beyond the hard perturbative process is at work. As a physically motivated attempt, we explore the ηc-mixing contribution, which adds coherently to the perturbative one and is comparable to it in the γη channel, and find that the interference can bring the ψ(2S) rates into agreement with the data, although its extraction is limited by a strong sensitivity to the mixing parameters.
Versions
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BibTeX
@misc{he2026radiative,
title = {{Radiative decays of $J/ψ,\,ψ(2S)\rightarrowγη^(\prime)$ in perturbative QCD with relativistic corrections}},
author = {Jun-Kang He and Chao-Jie Fan and Cong Wang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2607.23737},
eprint = {2607.23737},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.23737},
}
RIS
TY - UNPB
TI - Radiative decays of J/ψ, ψ(2S)→γη^(′) in perturbative QCD with relativistic corrections
AU - Jun-Kang He
AU - Chao-Jie Fan
AU - Cong Wang
PY - 2026
DA - 2026/10/30
PB - arXiv
DO - 10.48550/arxiv.2607.23737
UR - https://arxiv.org/abs/2607.23737
AB - We present the first calculation of the radiative decays J/ψ,ψ(2S)→γη^(′) in perturbative QCD that includes the order-q^2 relativistic corrections in all three short-distance contributions, namely the quark-antiquark, two-gluon, and QED contributions. The amplitudes are found to be remarkably insensitive to the light-cone distribution amplitude and to the light-quark mass, a robustness that persists through order q^2 and makes the predictions correspondingly reliable. The relativistic correction enhances the J/ψ branching ratios by roughly a factor of 2, narrowing their shortfall from experiment, whereas for the ψ(2S) it is about twice as large as for the J/ψ and the low-order expansion converges poorly. In two representative η--η^′ mixing schemes, the ratio ℛ_1S=ℬ(γη^′)/ℬ(γη) proves sharply sensitive to the mixing angle and favors the smaller of the two. The predicted ψ(2S) rates lie well above the data in both channels, already at leading order, and most severely for the anomalously small γη channel. Such a discrepancy suggests that a mechanism beyond the hard perturbative process is at work. As a physically motivated attempt, we explore the η_c-mixing contribution, which adds coherently to the perturbative one and is comparable to it in the γη channel, and find that the interference can bring the ψ(2S) rates into agreement with the data, although its extraction is limited by a strong sensitivity to the mixing parameters.
ER -