Inclusive Radiative psi(2S) Decays

TL;DR

This study measures the ratio of direct photon emission to three-gluon decay in psi(2S) particles, providing insights into quantum chromodynamics and charmonium decay mechanisms.

Contribution

It presents the first precise measurement of the direct photon to three-gluon decay ratio in psi(2S) decays using CLEO-c data, extending understanding of charmonium decay processes.

Findings

The ratio R(z>0.4) is 0.070 with combined uncertainties.

The measured R is about two-thirds of the corresponding J/psi(1S) value.

Results improve constraints on theoretical models of charmonium decays.

Abstract

Using e+e- collision data taken with the CLEO-c detector at the Cornell Electron Storage Ring, we have investigated the direct photon spectrum in the decay psi(2S)->gamma+gluon+gluon. We determine the ratio R of that inclusive direct photon decay rate to that of the three-gluon decay rate psi(2S)->3-gluon to be R(z>0.4)=0.070+/-0.002+/-0.019+/-0.011, with z defined as the scaled photon energy relative to the beam energy. The errors shown are statistical, systematic, and that due to the uncertainty in the input branching fractions used to extract the ratio, respectively. This R value is approximately 2/3 of the comparable value for the J/psi(1S), both in the region z>0.4, and also when extrapolated to the full range z>0.