MEERA VIEIRA MACHADO

A thesis submitted for the degree of Doctor of Philosophy defended April 2019.

The PhD School of Science, Faculty of Science, NBIA, Niels Bohr Institute, University of Copenhagen

Supervisor:
Kim Splittorff

Co-Supervisor:
Poul Henrik Damgaard

GEOMETRY IN HEAVY IONS: ESTIMATING AN ANGULAR POWER SPECTRUM

Anisotropies found in the final state of heavy ion collisions carry a plethora of information on the creation, expansion and decoupling of the quark-gluon plasma. From the types of fluctuations present in initial conditions, to how jets interact with the medium, to quantum correlations between pairs of identical particles. At the same time, there is an overabundance of studies in azimuthal anisotropies in comparison to longitudinal ones.

This work proposes an analysis of correlations between particle pairs projected on a sphere. In other words, the objective lies in estimating an angular power spectrum of heavy ions. The data set at hand pertains to Pb-Pb collisions at p sNN = 2:76 TeV measured by ALICE. Moreover, the selected events belong to the following phase space: jj < 0:9, 0   < 2 and 0:15 < pT < 100 GeV.

The method for power spectrum estimation is developed under three main considerations: limited pseudorapidity coverage, typical event multiplicity and detector efficiency. The results are first tested on toy Monte Carlo simulations and later applied to heavy ion data. These are shown for five different centralities, ranging from 0-5% to 30-40%. Then, flow harmonics are extracted and compared to other methods of calculation. At last, spectra are computed for separate transverse momentum intervals pT < 0:54 GeV and pT > 0:54 GeV, with each exerting dominance at distinct scales.