Precise decay rates for $\eta_c\to\gamma\gamma$ and $\eta_b\to\gamma\gamma$ from lattice QCD
Year: 2024
Type: conference-paper
Abstract: The measurement of the decay rates $\ecgg$ and $\ebgg$ are part of the BES III and Belle II programmes respectively as tests of the Standard Model. Here we provide, for the first time, precise SM values for these decay rates using lattice QCD. For $\Gec$ we obtain $6.788(61)\keV$ in good agreement with, but much more accurate than, experimental results using $\gamma\gamma\to\eta_c\to K\bar{K}\pi$. Our value is in 4 sigma tension with the PDG global fit result, however. Building on this study, we have been able to predict $\Geb=0.526(30)\keV$. We also compare the ratio of the form factors to the meson decay constants with expectations from NRQCD to assess how well nonrelativistic effective theories work in these two cases.
DOI: 10.22323/1.476.0473
Authors: Brian Colquhoun, Christine Davies, G. Peter Lepage
Institutions: University of Glasgow, Cornell University
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
OpenAlex ID: W4405563441