PhD in subatomic physics (M/F) – Quarkonia production in proton-proton and nucleus-nucleus collisions at LHC in ALICE experiment

Ultra-relativistic heavy ion collisions delivered by the CERN Large Hadron Collider (LHC) provides extreme conditions of temperature and density of nuclear matter allowing the study of Quark Gluon Plasma, a deconfined state of quarks and gluons, predicted by Quantum ChromoDynamics (QCD).

Quarkonia, pairs of heavy quark and anti-quark, are produced very early during a heavy ion collision. Therefore, they are very useful to understand the initial stages of such collisions and characterize the QGP evolution and properties. Indeed, they are very sensitive to the temperature of the medium created during the heavy ion collision. If the temperature is high enough, the charmed quark pairs initially produced will be dissolved in the medium. This phenomenon is called quarkonia suppression. 

The measurements done at LHC during Run 1 and 2 shed a new light on quarkonia production mechanisms. In particular, the J/ψ suppression is not as high as expected in the most central collisions. Indeed, the massive production of charm quarks at the LHC energies allows these quarks, after interaction in QGP, to form a new quarkonia state. This regeneration mechanism could explain the observed production of charmonia. 

However, the constraints that such measurements provide on theoretical models are still limited since the measurements are done on inclusive charmonia production. The Run 3 at LHC allows to separate the charmonia directly produced during the collisions from the ones produced by other particle decays such as B meson. The separation of these two components is necessary to understand the production and interaction with the medium of charmonia. This is possible in Run3 with ALICE thanks to the new Muon Forward Tracker detector that has been installed in the experiment. 

The goal of the PhD will be to study the quarkonia production in the muon decay channel at forward rapidities using data collected during the Run3 ALICE data taking in pp, pO, Ne-Ne, OO and/or Pb-Pb. The candidate will be involved in the data analysis on one of the topics of interest currently explored by the group.

This thesis focuses on the study and understanding of the mechanisms governing the production and interaction of heavy flavors in a quark-gluon plasma within the ALICE experiment. The Subatech laboratory has made a significant contribution to the design, construction, and implementation of the Muon Forward Tracker detector within ALICE for the 2022–2026 data run. The goal of this thesis is to analyze the data collected with this detector in order to separate the charm and beauty contributions in quarkonium production. Additionally, one of the key objectives of this thesis will be the development of machine learning-based algorithms for data analysis.