Bottomonium spectroscopy in the quark-gluon plasma

TL;DR

This paper reviews recent research on how the properties and dissociation mechanisms of bottomonium states are altered in the quark-gluon plasma created in heavy-ion collisions, highlighting the roles of screening, damping, and gluon dissociation.

Contribution

It summarizes recent findings on bottomonium suppression mechanisms in the QGP, including the effects of screening, damping, gluon dissociation, and feed-down, with comparisons to experimental data.

Findings

Transverse-momentum and centrality data match model predictions in Pb-Pb collisions.

Cold nuclear matter effects are significant but hot-medium effects are also observed.

Evidence supports the formation of a quark-gluon droplet in small systems like p-Pb.

Abstract

The spectroscopic properties of heavy quarkonia are substantially different in the quark-gluon plasma (QGP) that is created in relativistic heavy-ion collisions as compared to the vacuum situation that can be tested in pp collisions at the same center-of-mass energy. In this article, a series of recent works about the dissociation of the Y(nS) and chi_b(nP) states in the hot QGP is summarized. Quarkonia dissociation occurs due to (1) screening of the real quark-antiquark potential, (2) collisional damping through the imaginary part of the potential, and (3) gluon-induced dissociation. In addition, reduced feed-down plays a decisive role for the spin-triplet ground state. Transverse-momentum and centrality-dependent data are well reproduced in Pb-Pb collisions at LHC energies. In the asymmetric p-Pb system, alterations of the parton density functions in the lead nucleus account for the leading fraction of the modifications in cold nuclear matter (CNM), but the hot-medium effects turn out to be relevant in spite of the small initial spatial extent of the fireball, providing additional evidence for the generation of a quark-gluon droplet.