Elliptic Flow Studies using Event Shape Engineering in Pb-Pb Collisions at ALICE

Abstract: Inn ultra-relativistic heavy-ion collisions, QCD matter undergoes a phase transition to a strongly interacting Quark Gluon Plasma (QGP) where quarks and gluons are deconfined. The expansion of this plasma is well described by ideal hydrodynamics, suggesting that it behaves like a perfect, reversible, liquid. The particles emerging from the expansion are then highly correlated, showing collective behaviour originating from the plasma. This phenomenon is called collective flow and introduces key observables in the study of the QGP called flow harmonics v_n that reflect the initial anisotropies in the collision. In this thesis, results on the elliptic flow harmonic v_2 are obtained using the Event Shape Engineering (ESE) technique applied to 2.76 TeV Pb-Pb collisions at ALICE. By selecting events in a narrow centrality bin and in a certain flow interval, it is possible to control the initial geometry of the collision volume. Elliptic flow is calculated using the Q-cumulant method for two- and four-particle correlations. Results are also presented on the fluctuation and non-flow bias on the v_2{2} and v_2{4} transverse momentum distributions.