Quarkonia production in (ultra-)peripheral PbPb collisions at LHCb

TL;DR

This paper reports measurements of coherent and photo-produced quarkonia in ultra-peripheral and peripheral PbPb collisions at the LHCb, providing new data that tests quantum chromodynamics models at high energies.

Contribution

It presents the first detailed differential cross-section measurements of extjpsi and extpsitwos in ultra-peripheral PbPb collisions at 5.02 TeV, and studies low transverse momentum extjpsi production in peripheral collisions.

Findings

Measured cross-sections of extjpsi and extpsitwos in ultra-peripheral collisions.

Observed extjpsi production at low transverse momentum in peripheral collisions.

Results align with or challenge existing theoretical models.

Abstract

The cross-sections of coherent \jpsi and \psitwos production in ultra-peripheral PbPb collisions at a nucleon-nucleon center-of-mass energy of $5.02\,\mathrm{TeV}$ are measured using a data sample collected in 2018 at $\lhcb$, and the differential cross-sections are measured separately as a function of transverse momentum and rapidity. The photo-production of \jpsi mesons at low transverse momentum is studied in peripheral PbPb collisions, \jpsi candidates are reconstructed through the prompt decay into \mumu in the rapidity region of $2.0<y<4.5$. These results significantly improve previous measurements and are compared to the latest theoretical predictions.