Reconsideration of the inclusive prompt photon production at the LHC with<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>k</mml:mi><mml:mi>T</mml:mi></mml:msub></mml:math>-factorization

Abstract

We reconsider the inclusive production of isolated prompt photons in $pp$ collisions at the LHC energies in the framework of ${k}_{T}$-factorization approach. Our analysis is based on the $\mathcal{O}(\ensuremath{\alpha}{\ensuremath{\alpha}}_{s})$ off-shell (depending on the transverse momenta of initial quarks and gluons) production amplitudes of ${q}^{*}{g}^{*}\ensuremath{\rightarrow}\ensuremath{\gamma}q$ and ${q}^{*}{\overline{q}}^{*}\ensuremath{\rightarrow}\ensuremath{\gamma}g$ partonic subprocesses and transverse momentum dependent (or unintegrated) quark and gluon densities in a proton, which are chosen in accordance with the Kimber-Martin-Ryskin prescription. We show that the subleading high-order $\mathcal{O}(\ensuremath{\alpha}{\ensuremath{\alpha}}_{s}^{2})$ contributions, not covered by the noncollinear evolution of parton densities, are important to describe latest LHC data.