Probing QGP droplets with charmonium in high-multiplicity proton-proton collisions

TL;DR

This paper investigates the presence of quark-gluon plasma droplets in high-multiplicity proton-proton collisions at 13 TeV by analyzing charmonium suppression patterns using hydrodynamic and quantum evolution models, supported by lattice QCD data.

Contribution

It introduces a novel approach combining hydrodynamics and Schrödinger equation to study charmonium suppression as a signal of QGP droplets in small collision systems.

Findings

Charmonium suppression correlates with medium temperature and multiplicity.

The ratio of $\sigma_{ ext{psi(2S)}}$ to $\sigma_{J/ ext{psi}}$ decreases with higher multiplicity.

Results align with LHCb data, indicating QGP formation in high-multiplicity pp collisions.

Abstract

We study the hot medium effects in high-multiplicity proton-proton (pp) collisions at $\sqrt{s_{NN}}=13$ TeV via the charmonium probes. The hot medium is described with the hydrodynamic model, while charmonium evolutions in the medium are studied with a time-dependent Schr\"odinger equation. The hot medium dissociation on charmonium is considered with the temperature-dependent complex potential parametrized with the results from lattice QCD calculations. The ratio $\sigma_{\psi(2S)}/\sigma_{J/\psi}$ of $J/\psi$ and $\psi(2S)$ production cross sections are calculated and compared with the LHCb experimental data in pp collisions. Our calculations explain the charmonium relative suppression in different transverse momentum and multiplicity bins. The suppression of this ratio is mainly affected by the effects of the deconfined medium. It is less affected by the initial effects before the generation of the heavy quark pair. We suggest this to be a clear signal of the small QGP droplets generated in high multiplicity pp collisions.