Contribution of QED Compton Scattering Subprocess to Prompt Photon Production in Collisions of Longitudinally Polarized Protons at NICA Energies

Abstract

Contributions of the subprocesses of mixed chromo-electrodynamic \(qg \to q\gamma \) and pure electrodynamic Compton scattering \(q\gamma \to q\gamma \) to the process of prompt photon production in the collision of longitudinal polarized protons are investigated. The dependence of the differential cross section on the sum of energies \(\sqrt s \) of colliding protons, transverse momentum \({{p}_{{\text{T}}}}\) of photons, the cosine of scattering angle \(\cos (\theta )\), and pseudorapidity of photons \(y\) is studied. It is shown that the polarization of initial particles strongly affects the total cross section and the differential distributions. The contribution of a purely electrodynamic Compton subprocess depends on the polarization, and for many ranges of kinematics, it is numerically important in the differential cross section of the process of prompt photon production at energies of the NICA accelerator and, accordingly, should be taken into account in the simulation and analysis of experimental data. The double-spin asymmetry of the prompt photon production process is calculated. It is shown that the contributions of subprocesses \(qg \to q\gamma \) and \(q\gamma \to q\gamma \) to the double spin asymmetry strongly depend on the polarization of initial particles.