Multiplicity dependence of J/ ψ production and QCD dynamics in p+ p collisions at √s = 13 TeV

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 pT transfer), the semi-hard processes of multiple interactions of partons might also lead to the production of heavy particles like J/ψ. At the LHC, an approximately linear increase of the relative J/ψ 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/ψ production using pQCD inspired event generator, PYTHIA8 tune 4C, in p+ p collisions at s=13 TeV by investigating relative J/ψ yield and relative ⟨ pT⟩ of J/ψ as a function of charged particle multiplicity for different hard-QCD processes. We have estimated a newly defined ratio, rpp=⟨pT2⟩i/⟨pT2⟩MB, to gain understanding of J/ψ production in high-multiplicity p+ p collisions. For the first time we attempt to study the nuclear modification factor-like observables (Rpp and Rcp) to describe the QCD medium formed in high-multiplicity p+ p collisions. © 2020, Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature.