Employing RHIC and LHC data to determine the transverse momentum dependent gluon density in a proton

Abstract

Transverse momentum dependent (TMD) parton distributions in a proton are important in high-energy physics from both theoretical and phenomenological points of view. Using the latest RHIC and LHC data on the inclusive soft hadron production in $pp$ and $AA$ collisions at small transverse momenta, we determine the parameters of the initial TMD gluon density derived in the framework of a quark-gluon string model at the low scale ${\ensuremath{\mu}}_{0}\ensuremath{\sim}1--2\text{ }\text{ }\mathrm{GeV}$ and refine its large-$x$ behavior using the LHC data on the $t\overline{t}$ production at $\sqrt{s}=13\text{ }\text{ }\mathrm{TeV}$. Then, we apply the Catani-Ciafaloni-Fiorani-Marchesini evolution equation to extend the obtained TMD gluon density to the whole kinematical region. In addition, the complementary TMD valence and sea quark distributions are generated. The latter are evaluated in the approximation where the gluon-to-quark splitting occurs at the last evolution step using the TMD gluon-to-quark splitting function. Several phenomenological applications of the proposed TMD quark and gluon densities to the LHC processes are discussed.