Center-of-mass energy dependence of intrinsic-kT distributions obtained from Drell-Yan production

The internal motion of partons inside hadrons has been studied through its impact on very low transverse momentum spectra of Drell-Yan (DY) pairs created in hadron-hadron collisions. We study DY production at next-to-leading order using the Parton Branching (PB) method which describes the evolution of transverse momentum dependent parton distributions. The main focus is on studying the intrinsic transverse momentum distribution (intrinsic-kT) as a function of the center-of-mass energy √ s. While collinear parton shower Monte Carlo event generators require intrinsic transverse momentum distributions strongly dependent on √ s, this is not the case for the PB method. We perform a detailed study of the impact of soft parton emissions. We show that by requiring a minimal transverse momentum, q₀, of a radiated parton, a dependence of the width of the intrinsic-kT distribution as a function of √s is observed. This dependence becomes stronger with increasing q₀.