The $\sin (2\varphi )$ azimuthal asymmetry in exclusive ${\pi }^0$ production

Abstract

The $\sin (2\varphi )$ azimuthal angular correlation between the transverse momenta of the scattered electron and the recoil proton in the $ep\to e^{\prime }{p}^{\prime }{\pi }^0$ process provides a probe for quark orbital angular momentum. We numerically calculate this asymmetry for the future Electron-Ion Collider (EIC) in the U.S. and China (EicC) kinematics using a light-front quark-scalar-diquark model, in which the light-front wave functions (LFWFs) are derived from the soft-wall AdS/QCD framework. We also investigate the properties of the valence quark angular momentum expressed in terms of helicity-independent and helicity-dependent parton distributions. This study aims to establish theoretical constraints on the asymmetry sensitive to the quark orbital angular momentum prior to its first experimental measurement.

Comments: 16 pages, 4 figures