# 8th Workshop of the APS Topical Group on Hadronic Physics

10-12 April 2019
Denver, CO
US/Mountain timezone
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# Contribution contributed talk

Denver, CO - Director's Row H

# The Dalitz decay and frame dependence of transition form factors in light-front dynamics

• Meijian LI

## Content

The radiative transitions between quarkonia states via the emission of a photon $\psi_A\to \psi_B\gamma$ have been studied extensively in the literature. In light-front dynamics, transition form factors are usually computed in the Drell-Yan frame, which limits the transfered momentum to the spacelike region. In this work, we explore the radiative transitions between vector and pseudoscalar quarkonia in more general frames, where we are able to access the form factors over the full kinematic region. We evaluate the frame dependence of the transition form factor for heavy quarkonia with light-front wave functions calculated from the valence Fock sector, and use it to help us understand the violation of Lorentz symmetry that arises from the Fock-space truncation. We also study the electromagnetic Dalitz decay $\psi_A\to \psi_B l^+l^-$, and predict the effective mass spectrum of the leptonic pair ($l = e,\mu$).