Multiplicity Dependence of J/$\psi$ Production and QCD Dynamics in $p+p$ Collisions at $\sqrt{s}$ = 13 TeV

TL;DR

This study investigates how quark and gluon interactions influence J/ψ production in high-multiplicity proton-proton collisions at 13 TeV, revealing insights into QCD dynamics and medium effects using PYTHIA8 simulations.

Contribution

It introduces a detailed analysis of quark and gluon contributions to J/ψ production dependence on multiplicity in high-energy p+p collisions, including new ratios and modified nuclear modification factors.

Findings

Linear increase of J/ψ yield with multiplicity observed.

Gluon interactions dominate J/ψ production at high multiplicity.

First estimation of $r_{pp}$ ratio and application of $R_{pp}$ and $R_{cp}$ in p+p collisions.

Abstract

In inelastic $p+p$ collisions, the interacting objects are quarks and gluons (partons). It is believed that there are multiple interactions between the partons in a single $p+p$ event. Recent studies of multiplicity dependence of particle production in $p+p$ collisions have gathered considerable interest in the scientific community. According to several theoretical calculations, multiple gluon participation in hadronic collisions is the cause of high-multiplicity events. If the interaction is hard enough (large $p_{\rm T}$ transfer), the semi-hard processes of multiple interactions of partons might also lead to production of heavy particles like J/$\psi$. At the LHC, an approximately linear increase of the relative J/$\psi$ yield with charged particle multiplicity is observed in $p+p$ collisions. In the present work, we have studied the contribution of quarks and gluons to the multiplicity dependence of J/$\psi$ production using pQCD inspired event generator, PYTHIA8 tune 4C, in $p+p$ collisions at $\sqrt{s} =$13 TeV by investigating relative J/$\psi$ yield and relative $\langle p_{\rm T} \rangle$ of J/$\psi$ as a function of charged particle multiplicity for different hard-QCD processes. We have estimated a newly defined ratio, $r_{pp} = {\langle p_{\rm T}^{2} \rangle}_{i}/{\langle p_{\rm T}^{2} \rangle}_{\rm MB}$, to understand J/$\psi$ production in high-multiplicity $p+p$ collisions. For the first time we attempt to study the nuclear modification factor like observables ($R_{\rm pp}$ and $R_{\rm cp}$) to understand the QCD medium formed in high-multiplicity $p+p$ collisions.