In the Quest for Quark-Gluon Plasma in pp Collisions at the LHC Energies Using J/ψ Suppression

Abstract

Collectivity is an essential feature of the strongly interacting matter formed in the deconfined phase of quarks and gluons in the nucleus-nucleus (A-A) collisions at relativistic energies. Extensive experimental evidence from heavy-ion collisions at RHIC and LHC energies has conclusively demonstrated the collective behavior. Moreover, the compelling observations of phenomena like strangeness enhancement serve as strong corroborative evidence, solidifying the existence of quark-gluon plasma in heavy-ion collision systems. In comparison, the formation of QGP in pp collisions is ignored so far due to the lack of particle number density in pp collisions. Thus over the decades, the pp collision systems have served as a baseline for heavy-ion collisions and helped in revealing the unconventional demeanour of the heavy-ion collisions. In contrast to that, recently, collective behavior and strangeness enhancement have been observed in pp collisions at the LHC energies. These observations suggest that the existence of a QGP-like medium in small systems cannot be ruled out completely if collision energy is large enough. Inspired by these observations, we attempt to investigate the existence of QGP-like medium in pp collisions at s = 5.02, 7 and 13 TeV collisions energies. We employ 1+1D second-order viscous hydrodynamics in this study to account for the QGP medium evolution. Further, we use the Unified Model of Quarkonia Suppression (UMQS) to explain the experimental data available in the form of the normalized charmonium yield with respect to the normalized charged-particle multiplicity. Our UMQS model contains possible QGP effects which govern the net quarkonia yield in ultra-relativistic collisions. Our theoretical study supports the idea of the existence of a QGP-like medium in ultra-relativistic pp collisions predominately in high multiplicity events. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.