The VII-th International Conference on the Initial Stages of High-Energy Nuclear Collisions : Initial Stages 2023

Elliptic flow fluctuations of charged and identified hadrons relative to the participant and spectator planes in heavy-ion collisions with ALICE

20 Jun 2023, 16:30

20m

Aud. 2 (H.C. Ørsted)

Oral The initial stages and nuclear structure in heavy-ion collisions Parallel Session 3

Speaker

Michael Rudolf Ciupek (Heidelberg University (DE))

Description

Measurements of different flow harmonics relative to the participant and spectator planes provide unique insight into the initial conditions and the space-time evolution of the quark-gluon plasma (QGP). Different particle-type dependencies of these flow harmonics allow to separate the effects of QGP evolution and initial state fluctuations. Elliptic flow coefficients ($v_{2}$) relative to the participant and spectator planes are measured by ALICE in Pb-Pb collisions for charged hadrons, pions, kaons, and protons at midrapidity as a function of transverse momentum and centrality. The spectator plane is reconstructed from the deflection of the neutrons using two Zero Degree Calorimeters. Comparison of the ratio of $v_{2}$ relative to the spectator and participant plane with the corresponding eccentricities predicted by the initial state models indicates a decorrelation between the neutron spectator and the reaction plane or an incomplete description of the spectator dynamics within these models. The particle-type dependence of the ratio between $v_{2}$ measured using two- and four-particle cumulants is compared with hydrodynamic model calculations coupled with quark coalescence and jet fragmentation, which suggests a significant influence of hadronic interactions on $v_{2}$ during the final stage of the collision evolution.

Presentation materials

MichaeCiupek_ALICE_v2_InitialStages2023.pdf