Speaker
Description
The Parton-Branching method (PB) allows the determination of Transverse Momentum Dependent (TMD) parton densities, which cover the region from very small to $k_T$. In the very small $k_T$ region, the contribution from the intrinsic motion of partons (intrinsic $k_T$) plays a role, but also contributions of very soft gluons, which are resummed in the evolution equation. A detailed study shows the importance of very soft gluons (below a resolvable scale) to both the integrated as well as TMD parton densities.
The PB TMD parton densities together with a NLO calculation for the hard process in the MC@NLO style are used to calculate the transverse momentum spectrum of Drell-Yan pairs over a wide mass range. The sensitivity to the intrinsic $k_T$-distribution is used to determine its free parameters. Starting from the PB-NLO-HERAI+II-2018 set2 TMD parton distributions, the width of the intrinsic $k_T$ -distribution is determined, resulting in a slightly larger width than in the default set.
The width of the intrinsic $k_T$-distribution is independent of the mass of the Drell-Yan pair and independent of the center-of-mass energy $\sqrt{s}$, in contrast to other approaches.
| Collaboration / Activity | DESY CMS |
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