Angular ordering effects in TMD parton distribution functions and Drell-Yan $q_{\bot}$ spectra

TL;DR

This paper investigates how soft-gluon angular ordering influences the evolution of TMD parton distribution functions and affects the precision of Drell-Yan $q_{ot}$ spectra predictions at the LHC, comparing different theoretical approaches.

Contribution

It introduces a new analysis of angular ordering effects on TMD evolution using the parton branching method and compares it with existing approaches like KMRW and CSS.

Findings

Angular ordering significantly impacts low $q_{ot}$ Drell-Yan spectra predictions.

Different ordering scenarios affect the theoretical accuracy of the spectra.

The study provides numerical comparisons of various soft-gluon resolution scales.

Abstract

We present new results of our studies of soft-gluon angular ordering effects on the evolution of both collinear and transverse momentum dependent (TMD) parton distribution functions, and discuss their implications for precision predictions of Drell-Yan transverse momentum spectra at the LHC. Our method is based on the parton branching (PB) approach. We compare this with the implementation of angular ordering in the Kimber-Martin-Ryskin-Watt (KMRW) approach and with the Collins-Soper-Sterman (CSS) approach. We illustrate numerically the effects of different ordering scenarios ($p_{\bot}$, angular ordering), including definitions of the soft-gluon resolution scale and scale in the running coupling, on the theoretical accuracy of predictions in the low transverse momentum region of Drell-Yan spectra measured at the LHC.