Measurements of quarkonia and tetraquark production in jets at LHCb

Cooke, Naomi ORCID: 0000-0002-4179-3700 (2023). Measurements of quarkonia and tetraquark production in jets at LHCb. University of Birmingham. Ph.D.

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Abstract

The main subject of this thesis is to understand the production of quarkonia in more detail. Previous measurements from LHCb and CMS have shown discrepancies between data and current Pythia 8 MC predictions when measuring the normalised cross section \(vs. z(J/\psi) \equiv p_{T}(J/\psi)/p_{T}\)(jet) for prompt \(J/\psi\)'s, where J\(/\psi\)'s are clustered into jets. Pythia 8 predicts an isolated peak at \(z(J/\psi) \simeq\) 1 in comparison to data which is less isolated. First, the implementation of incorporating quarkonia fragmentation functions into the Pythia 8 parton shower framework is discussed. The incorporated calculations are based on the effective field theory, non-relativistic QCD (NRQCD). Second, Run 2 data collected by LHCb is used to measure normalised cross sections \(vs. z\) for different quarkonia, namely the J\(/\psi, \psi(2S)\), \(\Upsilon(1S)\), \(\Upsilon(2S)\) and \(\Upsilon(3S)\), for jets with \(p_{T} >\) 15 GeV. These are selected using the dimuon decay channel, where the \(\Upsilon\)'s are more isolated than the prompt \(J/\psi\) and \(\psi(2S)\). Finally, the normalised cross section \(vs. z\) is measured for the X(3872), to better understand its production using the dimuon-dipion decay channel, alongside the \(\psi(2S)\) for jets with \(p_{T} >\) 5 GeV. Contributions to the LHCb Upgrades are also discussed, in particular work to characterise Low Avalanche Gain Detectors (LGADs) produced by \(Micron\), before and after irradiation. These are a proposed timing-detector candidate for LHCb Upgrade 2.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):