Updating TMD parton densities in a proton within the Kimber-Martin-Ryskin approach

TL;DR

This paper derives analytical expressions for TMD parton densities in a proton using the Kimber-Martin-Ryskin approach, incorporating QCD evolution and fitting to experimental data, with applications to LHC b-jet production.

Contribution

It provides new analytical formulas for TMD parton densities at leading order, valid across small and large x, and includes phenomenological fits to experimental data.

Findings

Analytical TMD gluon and quark densities derived at leading order.

Good agreement with experimental data on proton structure functions.

Application to inclusive b-jet production at LHC demonstrated.

Abstract

We present analytical expressions for the Transverse Momentum Dependent (TMD, or unintegrated) gluon and quark densities in a proton derived at leading order of QCD running coupling and valid at both small and large x. The calculations are performed using the Kimber-Martin-Ryskin/Watt-Martin-Ryskin prescription (in both differential and integral formulations) with different treatment of kinematical constraint, which reflects the angular and strong ordering conditions for parton emissions. As an input, analytical solution of QCD evolution equations for conventional (collinear) parton distributions is applied, where the valence and non-singlet quark parts obey the Gross-Llewellyn-Smith and Gottfried sum rules and momentum conservation for the singlet quark and gluon densities is taken into account. Several phenomenological parameters are extracted from combined fit to precision data on the proton structure function $F_2(x,Q^2)$ collected by the BCDMS, H1 and ZEUS Collaborations, comprising a total of 933 points from 5 data sets. Comparison with the numerical results obtained by other groups is presented and phenomenological application to the inclusive b-jet production at the LHC is given.