Multiplicity dependence of J/ ψ production and QCD dynamics in p+p collisions at √(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_T 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 ⟨ p_T⟩ of J/ ψ as a function of charged particle multiplicity for different hard-QCD processes. We have estimated a newly defined ratio, r_pp = ⟨ p_T^2⟩_i/⟨ p_T^2⟩_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 ( R_pp and R_cp ) to describe the QCD medium formed in high-multiplicity p+p collisions.