Gamma-gamma physics and meson transition form factors

Andrzej Kupsc

doi:10.1051/epjconf/202023401008

Abstract

I summarize recent experimental results for two photon production of mesons. These processes include the neutral pion, η and η′ transition form factors and two photon production of pseudoscalar meson pairs. In addition I discuss the related hadronic and radiative processes. All these processes are attracting attention of experiment and theory due their relevance for the hadronic light-by-light contribution to the muon anomalous magnetic moment.

Highlights

Two photon interactions with mesons and mesonic systems are an important ingredient in the detailed understanding of the nature of mesons and their underlying quark and gluon structure
A transition form factor FP(q21, q22) is a scalar function of the four-momentum transfer squared of the virtual photons (q21,2) describing the vertex in Fig. 1(a) and defined as [18, 19]: A(P → γ∗γ(∗)) = qμ1
Analyses to extract single off shell transition form factors (TFFs) (q21 < 0 and q22 = 0) for π0 are underway by BESIII with preliminary results ing results for the bη(0) slope parameter are given in Table

Summary

Introduction

Two photon interactions with mesons and mesonic systems are an important ingredient in the detailed understanding of the nature of mesons and their underlying quark and gluon structure. The main motivation of the related studies is determination of hadronic contribution to the muon anomalous magnetic moment (g − 2)

Transition Form Factors

Two photon production of pseudoscalar meson pairs

Findings

Other related data