Prompt photon production in proton collisions as a probe of parton scattering in high energy limit

Abstract

We study the prompt photon hadroproduction at the LHC with the $k_T$-factorization approach and the $q{g}^{\ast }\to q\gamma$ and $g^{\ast }{g}^{\ast }\to q\bar{q}\gamma$ partonic channels, using three unintegrated gluon distributions which depend on gluon transverse momentum. They represent three different theoretical schemes which are usually considered in the $k_T$-factorization approach, known under the acronyms: KMR, CCFM and GBW gluon distributions. We find sensitivity of the calculated prompt photon transverse momentum distribution to the gluon transverse momentum distribution. The predictions obtained with the three approaches are compared to data, that allows to differentiate between them. We also discuss the significance of the two partonic channels, confronted with the expectations which are based on the applicability of the $k_T$-factorization scheme in the high energy approximation.

Comments: 23 pages, 10 figures, version accepted for publication in PRD