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arXiv · 2508.15181

The $\sin(2\phi)$ azimuthal asymmetry in exclusive $\pi^0$ production

Chentao Tan·Zhun Lu
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Abstract

The $\sin(2\phi)$ 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.

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Chentao Tan, Zhun Lu. 2025-08-21. The $\sin(2\phi)$ azimuthal asymmetry in exclusive $\pi^0$ production. https://arxiv.org/abs/2508.15181

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