Radiative Transitions in Charmonium from Lattice QCD

TL;DR

This paper uses lattice QCD to study radiative transitions in charmonium mesons, providing new computational methods and the first dynamical lattice results for certain form factors and amplitudes.

Contribution

Develops robust lattice QCD methods to compute radiative form factors and transitions, including excited states, for charmonium mesons.

Findings

Calculated form factors for low-lying charmonia

Demonstrated methods for excited state amplitudes

Provided first dynamical lattice QCD results for some quantities

Abstract

The coupling of various charmonium mesons to a photon is studied using lattice QCD, giving access to radiative form factors and transitions, and probing the mesons' structure. Methods are developed which allow the robust determination of amplitudes, including those involving an excited state as well as multiple form factors, for a range of kinematics. These are applied in dynamical lattice QCD calculations using the distillation technique to compute the underlying three-point correlation functions. Form factors and amplitudes involving the low-lying charmonia, $\eta_c$, $J/\psi$, $\chi_{c0}$ and $\eta_c'$, are calculated, demonstrating the methods and providing the first dynamical lattice QCD results for some quantities.