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

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.