Extraction of charmonium branching fractions from J/ψ→γηc radiative decays
Abstract
We assess the tension between theoretical predictions and the values quoted by the Particle Data Group (PDG) for the partial decay width and branching fraction associated with the radiative charmonium decay J/ψ→γηc. A profile scan over the most recent PDG data depending on the branching fraction ℬ(J/ψ→γηc) suggests that the correlation between measured branching fractions is compatible with lattice QCD determinations of the partial decay widths Γ(J/ψ→γηc) and Γ(ηc→γγ). We propose a theoretically grounded photon line shape for the radiative decay spectrum and a prescription for the extraction of (product) branching fractions involving the magnetic dipole (M1) transition J/ψ→γηc. This approach obviates the need to modify the photon energy spectrum line shape using empirical damping functions, as done in the most recent experimental extractions of ℬ(J/ψ→γηc) from the photon line shape, thereby eliminating an inherent ambiguity in the determination of the derived observables.
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BibTeX
@misc{schaaf2026extraction,
title = {{Extraction of charmonium branching fractions from $J/ψ\toγη_c$ radiative decays}},
author = {Magnus C. Schaaf and Antonio Vairo},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2606.19902},
eprint = {2606.19902},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.19902},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Extraction of charmonium branching fractions from J/ψ→γη_c radiative decays
AU - Magnus C. Schaaf
AU - Antonio Vairo
PY - 2026
DA - 2026/10/13
PB - arXiv
DO - 10.48550/arxiv.2606.19902
UR - https://arxiv.org/abs/2606.19902
AB - We assess the tension between theoretical predictions and the values quoted by the Particle Data Group (PDG) for the partial decay width and branching fraction associated with the radiative charmonium decay J/ψ→γη_c. A profile scan over the most recent PDG data depending on the branching fraction ℬ(J/ψ→γη_c) suggests that the correlation between measured branching fractions is compatible with lattice QCD determinations of the partial decay widths Γ(J/ψ→γη_c) and Γ(η_c→γγ). We propose a theoretically grounded photon line shape for the radiative decay spectrum and a prescription for the extraction of (product) branching fractions involving the magnetic dipole (M1) transition J/ψ→γη_c. This approach obviates the need to modify the photon energy spectrum line shape using empirical damping functions, as done in the most recent experimental extractions of ℬ(J/ψ→γη_c) from the photon line shape, thereby eliminating an inherent ambiguity in the determination of the derived observables.
ER -