Multiplicity dependence of ${\rm Y}$(nS) mean transverse momentum in proton-proton collisions

Abstract

Correct description of quarkonia production and kinematics are still one of the most challenging assignments for Quantum Chromodynamics. This document presents a study of the ${\rm Y}$(1S), (2S) and (3S) mean transverse momentum ($⟨p_{\mathrm{T}}^{{\rm Y}}⟩$) as a function of the charged particle multiplicity ($N_{\mathrm{Track}}$) in proton-proton collisions at $\sqrt{s}$ = 7 TeV generated with Pythia 8.312 CUETP8M1 tune. The comparison to real data collected by the CMS experiment indicates that the agreement is much better for the excited states than for the ground state. The observed fast increase of the $⟨p_{\mathrm{T}}^{{\rm Y}}⟩$ at small values of $N_{\mathrm{Track}}$ is mainly due to the contribution from the away region. Furthermore, when computing the $⟨p_{\mathrm{T}}^{{\rm Y}}⟩$ from jetty and isotropic events a clear $p_{\mathrm{T}}$ hardening is observed in jetty events. Finally, analyzing the fragmentation of jets containing an ${\rm Y}$(nS) it is proposed a method to test the new quarkonia shower present in the Monte Carlo event generator.

7 pages, 4 figures

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