Measurement of the centrality dependent nuclear modification factor of the D*+ meson

Abstract

Quark-gluon plasma (QGP) is thought to have permeated the early universe briefly in the first moments after the Big Bang. Therefore, research into this new state of matter is pivotal to understanding the development of the cosmos. At the LHC, specialised detectors such as ALICE use heavy-ion collisions to simulate the conditions present at the Big Bang and thus produce and study this plasma. Since QGP is strongly interacting, it can be probed effectively by quantifying its influence on heavy-flavour quarks travelling through it. One of the most known observables is the nuclear modification factor (RAA), which quantifies the in-medium collisional and radiative energy loss of subatomic particles travelling through the hot and dense plasma. This thesis investigated the relation between RAA and collision geometry for charm quarks, hypothesising that larger charm suppression would be found for more head-on (central) collisions of ions, indicating generation of larger and hotter QGP for these types of collisions. This was indeed found to be the case. The results were also compared to a theoretical model of RAA including in-medium energy loss. It was found to be in good agreement with the data, within the relatively large statistical and systematic uncertainties of the measurement.