Measurement of the Central Exclusive Production of the p0 meson with LHCb Experiment

This thesis presents a measurement of the Central Exclusive Production (CEP) of the neutral rho vector meson, using proton-lead ion collision data taken using the LHCb detector, during the LHC's Run 2 in 2016. The result is measured differentially in rapidity, invariant mass, and squared transverse momentum. In CEP, only one or two new particles are produced, while the colliding particles remain intact. The process is referred to as exclusive since the final state is completely determined. The process proceeds via a scattering between the proton and a quasi-real photon, and with the proton-ion dataset as well as the asymmetric lever-arm design of the LHCb detector, this allows for the direction of the photon to be determined unambiguously. This results in the production of a vector meson, which is subsequently put on-mass-shell through the exchange of the vacuum quantum numbers in the form of the pomeron trajectory. The mass of the produced vector meson sets the energy scale, and hence a measurements of neutral rho meson production provides insight into the transition between the soft and hard QCD regimes. The hadronic and photo production cross-sections are measured in bins of rapidity, with the results interpreted assuming a linear pomeron trajectory, within the context of Regge theory. The average values for the photo-production cross-section, across the rapidity bins, is found to be 7.1 ± 0.1 (stat) ± 0.1 (sys) μb and 23.5 ± 0.7 (stat) ±1.4 (sys) μb for the p-Pb and Pb-p data, respectively. The extracted values for the pomeron intercept and slope are 1.105 ± 0.01 (stat), and 0.175 ± 0.003 (stat), respectively. In addition, values for the nominal mass and width of the neutral rho meson are extracted through fits to the invariant mass distributions in bins of rapidity. Combining the measurements yields a value for the width: 156 ± 2 (stat) ± 7 (sys) MeV, and for the mass: 772 ± 1 (stat) ± 2 (sys), consistent within uncertainties with values reported by the PDG.