Photon Transitions in \psi(2S) Decays to \chi_{cJ}(1P) and \eta_c(1S)

TL;DR

This study provides precise measurements of photon transition rates in psi(2S) decays, confirming some transitions and refuting others, thereby refining understanding of charmonium state transitions.

Contribution

The paper presents the most precise measurements of E1 photon transition rates in psi(2S) decays and confirms the hindered M1 transition, while disputing a previously observed M1 transition.

Findings

Precise E1 transition rates for psi(2S)--> gamma chicJ(1P)

Confirmation of the hindered M1 transition psi(2S)-->gamma etac(1S)

Non-observation of the psi(2S)-->gamma etac(2S) transition at 91 MeV

Abstract

We have studied the inclusive photon spectrum in psi(2S) decays using the CLEO III detector. We present the most precise measurements of electric dipole (E1) photon transition rates for psi(2S)--> gamma chicJ(1P) (J=0,1,2). We also confirm the hindered magnetic dipole (M1) transition, psi(2S)-->gamma etac(1S). However, the direct M1 transition psi(2S)-->gamma etac(2S) observed by the Crystal Ball as a narrow peak at a photon energy of 91 MeV is not found in our data.