Single isolated photon production in the NLO${}^\star$ approximation of the Parton Reggeization Approach

Abstract

The hadroproduction of single isolated photon at high energies is studied within the framework of the NLO${}^\star$ approximation of the Parton Reggeization Approach based on the modified Multi-Regge limit of the hard scattering QCD amplitudes. The contribution from the LO subprocess $Q \bar Q \to \gamma$ and the NLO tree-level corrections $Q R \to \gamma q$ and $Q \bar Q \to \gamma g$ are considered. To avoid specific double counting in rapidity between tree-level corrections to the hard scattering coefficient and unintegrated PDFs, a corresponding subtraction scheme is proposed. We demonstrated self-consistency of the Parton Reggeization Approach using the subtraction scheme. The results of calculations are compared with data from various Collaborations in the wide energy range $\sqrt{S} = 24 \ {\rm GeV} - 13 \ {\rm TeV}$. We obtained a quite satisfactory agreement with data up to $p_T^\gamma / \sqrt{S} \simeq 0.2 - 0.3$. Predictions for the future SPD NICA experiment were discussed.