J/$\psi$ and $\Upsilon$(1S) production in jets at LHC energies

TL;DR

This paper investigates quarkonia production in jets at the LHC, demonstrating that incorporating a new quarkonia parton shower in PYTHIA 8.312 improves agreement with experimental data and suggests strategies to distinguish between different QCD models.

Contribution

It introduces a new quarkonia parton shower in PYTHIA 8.312 and shows its effectiveness in matching experimental data on J/ψ and Υ(1S) production in jets.

Findings

The new quarkonia parton shower improves data simulation accuracy.

QCD color reconnection effects are consistent with experimental observations.

Higher jet pT selections can help distinguish between different PYTHIA 8 models.

Abstract

Quarkonia production in hadronic collisions is far from being understood as none of the existing models can correctly describe the wealth of available data. In particular, LHCb and CMS experiments have reported that PYTHIA 8 cannot reproduce the prompt J/$\psi$ production in jets in proton-proton collisions at two different center of mass energies: the event generator predicts an important amount of the prompt J/$\psi$ to be produced isolated, opposite to the experimental data. This document demonstrates that such effect remains true even if the QCD color reconnection (CR) model is used. Besides that, it is shown that using the new quarkonia parton shower included in PYTHIA 8.312 it is possible to correctly describe the experimental results. This agreement between data and simulation is improved when using the QCD color reconnection approach, opening the possibility to distinguish between the two CR implementations. Finally, a prediction performed for $\Upsilon$(1S) indicates that a higher jet p$_T$ selection should be used by the LHC experiments in order to distinguish between PYTHIA 8 results generated with and without the quarkonia parton shower.