Exclusive Observables to NLO and Low x PDF Phenomenology at the LHC



Flett, Christopher
(2021) Exclusive Observables to NLO and Low x PDF Phenomenology at the LHC. PhD thesis, University of Liverpool.

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Abstract

At present, the Parton Distribution Functions~(PDFs) for the quarks and gluons of QCD extracted in global fitting analyses suffer from large uncertainties, particularly at low $x$ and low scales. This is mainly a reflection of the lack of experimental data constraints in this kinematical regime. In this thesis, due to its enhanced sensitivity to the gluon PDF, we will study the exclusive production of heavy vector mesons $V$, measured recently in ultra peripheral $pp$ collisions at the LHC, $pp \rightarrow p\,+\,V\,+\,p$, as a means to reliably constrain, probe and determine the gluon PDF in the very low $x$ domain. With the advent of new and improved colliders on the horizon, PDF phenomenology is becoming more and more important at low $x$ as particle collision energies increase. The data for the exclusive production of the $J/\psi$ meson from LHCb, specifically, will be promoted as being at the frontier of new low $x$ and low scale gluon PDF constraints, providing the driving force in allowing this kinematic regime to start, and ultimately become, an area of precision physics. Using a fully furnished prediction for exclusive $J/\psi$ photoproduction within the collinear factorisation framework at NLO, a low $x \sim 10^{-5}$ and low scale $\mu^2 \sim 2.4\,\text{GeV}^2$ gluon PDF is obtained within a statistical reweighting framework using existing HERA and LHC exclusive data. The significance of this result for low $x$ global gluon PDF extractions is quantified. Finally, we build and use a computational workhorse to extract the exclusive {\it electro} production of heavy vector mesons to NLO in collinear factorisation. This completes the $Q^2$ phase space for this observable and provides a calculation that is on solid grounds with regards to the applicability of the factorisation ansatz.

Item Type: Thesis (PhD)
Divisions: Faculty of Science and Engineering > School of Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 04 Jun 2021 10:29
Last Modified: 18 Jan 2023 22:46
DOI: 10.17638/03123138
Supervisors:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3123138