Nonadiabatic evolution of charmonium states and its impact on the ψ′ yield and ψ′ /( J/ψ ) yield ratio in high multiplicity p + p collisions

The suppression in the yield of quarkonia (heavy quark-antiquark bound states) has long been considered a key signature of the formation of thermalized deconfined partonic matter, known as the Quark Gluon Plasma (QGP), in Relativistic Heavy-Ion Collision Experiments. Conventionally, the in-medium dissociation of quarkonium states has been presented by implicitly assuming an adiabatic approximation, which entails the heavy quark Hamiltonian changing slowly over time owing to the evolving medium. However, in high multiplicity small systems, such as in p + p collisions, the early development of transverse flow due to the finite transverse size of the locally thermalized medium may cause quarkonium states to undergo nonadiabatic evolution. We study the effect of such nonadiabaticity on the evolution of J/ψ and ψ′ states. We argue that J/ψ yield can be affected due to the nonadiabatic effects. Moreover, we also observe the enhancement in the yield ratio of ψ′ to J/ψ (i.e., ψ′/(J/ψ)), along with a simultaneous enhancement in ψ′ yield. Our findings are based on realistic modeling of the time evolution of small systems, where for the bulk evolution of the system, we consider a 2+1D MUSIC hydrodynamic code along with proper modeling of the pre-equilibrium dynamics. We also discuss the possible implications of such an enhancement of the yield ratio in the context of the formation of deconfined matter in high multiplicity p + p collisions. We have also calculated the nuclear modification factor (R AA ) for different quarkonia states. The variation of (R AA ) with charge particle multiplicity (dN ch /dη) can be used to compare the theoretical calculation with experimental data whenever available.