Feasibility Studies towards Accessing Generalised Distribution Amplitudes in Exclusive γ-Meson and γγ Production with PANDA at FAIR

Abstract

Understanding the fundamental properties and interactions of the proton remains a central focus in contemporary hadron physics. Its internal structure and the dynamics of hadronic interactions can be explored through exclusive reactions involving antiproton–proton annihilation. This work presents a study of three exclusive channels: $\bar{p}$p → π⁰γ, $\bar{p}$p → π⁰π⁰, and $\bar{p}$p → γγ, with a focus on their potential to probe nucleon structure and reaction dynamics. The studies are performed at four discrete beam momenta of 2.5, 5, 10, and 15 GeV/c. These investigations are carried out in the framework of the PANDA experiment at the upcoming FAIR facility in Darmstadt, which will utilize a high-intensity antiproton beam in the momentum range of 1.5–15 GeV/c. Data samples for both the signal and all relevant background channels were generated and simulated using the PANDARoot framework. This study includes the optimization of the signal-to-background ratio, estimation of count rates, and determination of expected cross sections along with their statistical uncertainties. The results demonstrate that all relevant background channels can be sufficiently suppressed, confirming the feasibility of measuring these reactions at PANDA with sufficient accuracy to significantly advance the understanding of hadron structure in the time-like regime.