Jet charge in pp and Pb-Pb collisions measured with the ALICE experiment at the LHC

Colburn, J Samuel (2024). Jet charge in pp and Pb-Pb collisions measured with the ALICE experiment at the LHC. University of Birmingham. Ph.D.

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Abstract

Jet charge is the momentum-weighted sum of a jet’s electric charges. The value of a jet’s given jet charge is influenced by the parton that initiated the jet. This influence shifts the net charge towards the charge of that progenitor parton. This property offers a way to study the energy-loss from the QGP. Generating templates for the jet charge distribution for a given progenitor parton using Monte Carlo (MC) data and then fitting these templates to real data allows jet yields to be extracted. Two different techniques were investigated for identifying the progenitor parton of the jet. The first of the techniques employs the structure of the MC data and framework. The second of these techniques selects the parton based on the constituent of the jet with the largest momentum.

The yields of jets produced from distinct types of parton have been measured in pp and Pb-Pb data at √sN N = in order to investigate the effects of the QGP on quark and gluon jets. It has been suggested that gluons will interact more strongly with the QGP when compared to quarks. Thus, gluon jets are expected to be more heavily suppressed by the QGP. The background subtraction in the Pb-Pb data was conducted using the constituent subtraction method. Suppression of gluon jets is found at medium centrality collisions (i.e. in the centrality range 40-80%); however, in the most central collisions, it is likely that the background-dominated environment prevents the jet charge distribution templates from being accurately fitted to the experimental data. In order to conclusively demonstrate gluon suppression by the QGP using measurements of the jet charge observable, a better method of handling the effects of jet charge in the most central collisions must be developed. This thesis presents the first measurements of jet charge at ALICE using Run 2 data.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):