📝 SummarXiv

Abstract

Consider the scattering of GeV energy beam particles off the Coulomb field of a nucleus. In this context, the Coulomb field behaves like a target of $\gamma^*$ virtual photons, with the target density being proportional to Z$^2$. Henry Primakoff was the first to describe how to determine the $\pi^0$ lifetime by measuring the production cross section for the process $\gamma\gamma^* \rightarrow \pi^0$. When a $\gamma$ ray beam is used, Primakoff scattering is effectively represents $\gamma\gamma^*$ scattering involving hundreds of MeV gamma rays. We begin by describing Primakoffs scientific career and personal life. Then, we will review his studies on Primakoff scattering related to pion polarizability and the $\gamma\rightarrow\pi\pi\pi$ chiral anomaly at CERN COMPASS, as well as the $\pi^0$ lifetime study carried out at Jefferson Laboratory (JLab). We highlight the good agreement between these studies and the predictions of 2-flavor (u,d) Chiral Perturbation Theory (ChPT). Additionally, we explain the necessity of future Primakoff reaction studies involving kaons and $\eta$ mesons to evaluate how effectively three-flavor (u, d, s) ChPT accounts for the effects of strange quarks.