Employing RHIC and LHC data to determine TMD gluon density in a proton

TL;DR

This paper determines the TMD gluon density in a proton using RHIC and LHC data, refining its parameters and evolution, and explores its applications to LHC processes.

Contribution

It introduces a novel method to extract TMD gluon densities from experimental data and extends them across the full kinematic range using CCFM evolution.

Findings

Determined initial TMD gluon density parameters from RHIC and LHC data.

Refined large-x behavior of TMD gluon density with 13 TeV LHC data.

Applied TMD distributions to various LHC processes.

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 quark-gluon string model at the low scale $\mu_0 \sim 1 - 2$ GeV and refine its large-$x$ behaviour using the LHC data on the $t \bar t$ production at $\sqrt s = 13$ TeV. Then, we apply the Catani-Ciafaloni-Fiorani-Marchesini (CCFM) 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.