Measuring the N-subjettiness jet shape in pp and Pb-Pb collisions with the ALICE experiment

Zardoshti, Nima ORCID: 0000-0002-6708-585X (2019). Measuring the N-subjettiness jet shape in pp and Pb-Pb collisions with the ALICE experiment. University of Birmingham. Ph.D.

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Abstract

Fully corrected measurements of the \(\tau_{2}/\tau_{1}\) jet shape are reported, in pp (\(\sqrt{s}=7 TeV\)) and Pb-Pb (\(\sqrt{s_{NN}}=2.76 TeV\)) collisions, using the ALICE detector. Fully corrected measurements of the \(\Delta\)R jet shape are also presented in pp collisions. For each shape, measurements are made using four different reclustering algorithms, which probe the hard and soft scale splittings of the jet substructure. These are the exclusive \(k_{T}\), exlcusive C/A (with and without minimisation) and soft drop groomer with C/A algorithms. In both collision systems, the shapes are presented at 40 \(\leq p^{jet, ch}_{T}\) with a jet resolution of \(R=0.4\). The semi-inclusive hadron-jet coincidence technique is extended to two dimensions for the first time, in order to reject the combinatorial background in Pb-Pb collisions. A two-dimensional Bayesian unfolding procedure is used to correct the measured distributions, for detector (pp and Pb-Pb) and background (Pb-Pb) effects.

In pp collisions, the results are used to test QCD splitting functions and fragmentation patterns, with particular emphasis on measuring the two-prong nature of QCD jets. In Pb-Pb collisions, changes to this two-prong substructure, due to quenching effects in the quark-gluon plasma, are investigated. No modifications, relative to the vacuum, are observed .

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):