Jet modification in absence of QGP-medium: the role of multiparton interactions and color reconnection

Recent studies on high-multiplicity events in small collision systems (proton-proton and proton-lead) have drawn considerable research interest toward the possibility of the formation of partonic medium in such systems. One of the important consequences of the formation of dense partonic medium is the quenching of high-momentum final-state particles, resulting in several experimental observations such as suppression in nuclear modification factor R-AA, modification of jet shape observable rho(r) and jet fragmentation (z(ch)) distributions, etc. In this work, we study rho(r) and z(ch) for inclusive charged-particle jets in proton-proton (pp) collisions at root s = 13 TeV using the PYTHIA 8 Monash 2013 Monte Carlo simulation. We show that the color reconnection (CR) and multiparton interaction (MPI) mechanisms in PYTHIA 8 can lead to an increased rate of jet production. We also find that the mechanisms of MPI and CR and change in the gluonic contribution in high-multiplicity events result in significant modification of rho(r) and z(ch) compared to those in minimum bias events for 10 < MPI > and gluonic contribution with the amount of modification in rho(r): the larger the number of MPIs and/or gluonic contribution, the larger the amount of modification of rho(r).