Production des bosons Z et du double charme avec ALICE auprès du LHC

par Sizar Aziz

Projet de thèse en Physique hadronique

Sous la direction de Zaida Conesa del valle et de Bruno Espagnon.

Thèses en préparation à université Paris-Saclay , dans le cadre de École doctorale Particules, Hadrons, Énergie et Noyau : Instrumentation, Imagerie, Cosmos et Simulat , en partenariat avec Laboratoire de Physique des deux Infinis Irène Joliot-Curie (laboratoire) et de Faculté des sciences d'Orsay (référent) depuis le 30-09-2018 .

  • Résumé

    The ALICE experiment at the LHC is dedicated to the study of the Quark-Gluon Plasma (QGP), a state of matter in which quarks and gluons, the fundamental blocks of nuclear matter are deconfined. Quantum Chromodynamics predicts a phase transition between ordinary nuclear matter and the QGP for an energy density of about 1-2 GeV/fm^3 and a temperature of about 200 MeV. The Universe may have gone through a QGP state a few microseconds after its formation. Ultra-relativistic heavy-ion collisions can create in the laboratory the extreme temperature and energy density conditions necessary to form the QGP. The created medium behaves as a quasi-perfect liquid of strongly coupled partons. Among the observables that probe the formation of the QGP, our group is particularly interested in the production of hard probes, occurring in the early stages of the collision that probe the whole medium evolution.

  • Titre traduit

    Z boson and double charm production with ALICE at the LHC

  • Résumé

    This PhD project focuses on measurements of the nuclear and collective effects which constitute the reference to interpret the measurements in Pb-Pb collisions, and are lacking of experimental constraints. The proposal is composed of two parts. The first part consists on the measurement of Z boson production in Pb-Pb collisions at √sNN= 5.02 TeV with 2018 data. Z bosons are weakly interacting probes, therefore they are insensitive to the QGP formation, and allow us to study the scaling of hard probes production with the number of colliding nucleons, as well as the modification of the parton distribution functions in nuclei. These effects are more important at large rapidities, which coincides with the acceptance of ALICE. The analysis of 2018 data will be combined with results from 2015 data, increasing the statistical precision by a factor of two. A systematic comparison with models will bring constraints. The second part of the project is centred on the study of the contribution of multiple parton interactions on the production of open charm, D mesons (formed by a c and light quark), and hidden charm, J/Ψ mesons (c-cbar bound state). This becomes possible by measuring their production rates as well as their angular correlation, which is a distinctive characteristic. An exploratory analysis of the correlation among the production of J/Ψ at large rapidity and D at central rapidity in pp collisions at √s = 13 TeV will be carried out. At the LHC, this analysis with a large angular rapidity gap represents a unique observable that is only accessible with the ALICE experiment. Results will be compared with model calculations. This exploratory analysis will also allow us to prepare for the run-III data-taking period (2021), in which a larger data sample with information from all sub-detectors will be accumulated.