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arXiv · 2602.12119

Studies of low energy $l+p\to l+p+\gamma$ process in covariant chiral perturbation theory

Xu Wang·Kai-Ge Kang·Zhiguang Xiao·Han-Qing Zheng
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Abstract

This study presents a tree-level calculation of the scattering amplitude for the $lp\to lp\gamma$ (with a hard photon) process within the framework of Chiral Perturbation Theory. Our calculations, based on the $O(p^2)$ and $O(p^3)$ nucleon-pion Lagrangians, aim to provide a theoretical prediction for the differential cross-section. The result shows that explicit inclusion of the nonzero lepton mass significantly influences the low energy differential cross section for $\mu p\to \mu p \gamma$ process. The kinematic region of the present experimental data is beyond the validity domain of the $\chi$PT and is therefore not suitable for determining the low-energy constants (LECs). By comparing our results with future experimental data, we expect to determine the values of the LECs as a further test of $\chi$PT as an effective low-energy theory of QCD. The process is of significant interest as it can help to determine the generalized polarizabilities of the nucleon.

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Xu Wang, Kai-Ge Kang, Zhiguang Xiao, Han-Qing Zheng. 2026-02-12. Studies of low energy $l+p\to l+p+\gamma$ process in covariant chiral perturbation theory. https://arxiv.org/abs/2602.12119

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