Recent progress in transverse momentum dependent (TMD) Parton Densities and corresponding parton showers

TL;DR

This paper investigates the role of soft gluons in TMD parton densities using the Parton-Branching method, revealing a non-perturbative Sudakov form factor that influences the transverse momentum spectrum in high-energy processes.

Contribution

It introduces a novel application of the PB method to identify the non-perturbative Sudakov form factor, highlighting its importance in TMD parton densities and parton shower modeling.

Findings

Soft gluons significantly affect TMD parton densities.

The intrinsic-$k_t$ distribution width is independent of $\

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Abstract

The parton branching method is crucial for Monte Carlo generators, which are essential for high-energy physics predictions. We examine the impact of soft gluons on inclusive collinear and Transverse Momentum Dependent (TMD) parton densities. By applying the Parton-Branching (PB) method, we identify the non-perturbative Sudakov form factor with the integration range $z \to 1$, which is often neglected in collinear parton shower approaches. The significance of soft gluons is demonstrated through the transverse momentum spectrum of Drell-Yan lepton pairs, resulting in an intrinsic-$k_t$ distribution width that remains independent of $\sqrt(s)$, contrary to observations in collinear parton shower approaches. This behavior is attributed to the non-perturbative Sudakov form factor.