Pseudorapidity dependence of long-range correlations - with ALICE in Pb-Pb, Xe-Xe, and p-Pb collisions

Year
2020
Degree
PhD
Author
Thoresen, Freja
Mail
freja.thoresen@cern.ch
Institution
Copenhagen U.
Abstract

At the LHC, the strongly interacting Quark-Gluon Plasma is created in heavy-ion collisions. The collisions can be studied at ALICE. One measurable of the created plasma is anisotropic flow. The anisotropic flow measurements are closely related to the initial conditions of the collision, and to the expansion of the plasma. This work presents flow measurements as a function of pseudorapidity with data from the Time-Projection Chamber (TPC) and the Forward Multiplicity Detector (FMD). The Generic Framework is used to calculate the flow coefficients. The non-uniform acceptance and non-uniform efficiency of the detectors can be corrected by using particle weights in the Generic Framework. The Forward Multiplicity Detector (FMD) at ALICE, needs further corrections since it receives background signal from particles created from material interactions. The flow coefficients, $v_n$, are presented over a large range in pseudorapidity ($-3.5 \leq \eta \leq 5$) in Pb$-$Pb collisions with $\sqrt{s}_\mathrm{NN}=5.02$ TeV, Xe$-$Xe with $\sqrt{s}_\mathrm{NN}=5.44$ TeV, and early results for p$-$Pb with $\sqrt{s}_\mathrm{NN}=5.02$ TeV. The flow coefficients are measured with 2- and 4-particle cumulants with $|\Delta \eta | > 0.8$ and $|\Delta \eta | > 2$. The difference between $v_2\{2,|\Delta \eta|>0.8\}$ and $v_2\{2,|\Delta \eta|>2\}$ implies changes in the decorrelation of the flow vectors or non-flow effects between the two methods. The decorrelation effect of the flow vectors is studied with a decorrelation ratio $r_{n,n}$, which is presented for Pb$-$Pb and p$-$Pb collisions with $\sqrt{s}_\mathrm{NN}=5.02$ TeV. The decorrelation of the flow vectors are more significant for p$-$Pb than for Pb$-$Pb. The AMPT model is compared to the flow measurements in pseudorapidity, and the comparisons show a qualitative agreement with the measurements.

Supervisors
Gaardhøje, Jens Jørgen (Copenhagen U.)
Report number
CERN-THESIS-2020-084
Date of last update
2021-02-22