Examining coupled-channel effects in radiative charmonium transitions

TL;DR

This paper proposes a method to examine coupled-channel effects in charmonium transitions, focusing on hindered M1 radiative transitions, with specific ratio measurements providing clear, parameter-free tests of these effects.

Contribution

It introduces a novel approach using hindered M1 transitions and specific ratio measurements to unambiguously identify coupled-channel effects in heavy quarkonium.

Findings

Parameter-free predictions for transition ratios.

Proposed measurements to test coupled-channel effects.

Applicability to lattice QCD calculations.

Abstract

Coupled-channel effects due to coupling of charmonia to the charmed and anticharmed mesons are of current interest in heavy quarkonium physics. However, the effects have not been unambiguously established. In this paper, a clean method is proposed in order to examine the coupled-channel effects in charmonium transitions. We show that the hindered M1 radiative transitions from the 2P to 1P charmonia are suitable for this purpose. We suggest to measure one or more of the ratios Gamma(h_c'-->chi_{cJ} gamma)/Gamma(chi_{cJ}'-->chi_{cJ} pi^0) and Gamma(chi_{cJ}'-->h_c gamma)/Gamma(chi_{cJ}'-->chi_{cJ} pi^0), for which highly nontrivial and parameter-free predictions are given. The picture can also be tested using both unquenched and quenched lattice calculations.