The small kTregion in Drell–Yan production at next-to-leading order with the parton branching method

The Parton Branching (PB) method describes the evolution of transverse momentum dependent (TMD) parton distributions, covering all kinematic regions from small to large transverse momenta kT k T . The small kT k T -region is very sensitive both to the contribution of the intrinsic motion of partons (intrinsic kT k T ) and to the resummation of soft gluons taken into account by the PB TMD evolution equations. We study the role of soft-gluon emissions in TMD as well as integrated parton distributions. We perform a detailed investigation of the PB TMD methodology at next-to-leading order (NLO) in Drell–Yan (DY) production for low transverse momenta. We present the extraction of the nonperturbative “intrinsic- kT k T ” distribution from recent measurements of DY transverse momentum distributions at the LHC across a wide range in DY masses, including a detailed treatment of statistical, correlated and uncorrelated uncertainties. We comment on the (in)dependence of intrinsic transverse momentum on DY mass and center-of-mass energy, and on the comparison with other approaches.