This thesis presents an analysis of the central exclusive production (CEP) of χ<sub>c</sub> mesons in proton-proton collisions at a centre-of-mass energy of 8 TeV, using data collected with the LHCb detector corresponding to an effective integrated luminosity of 126.3 ± 4.3 pb⁻¹. Candidate χ<sub>c</sub> decays are reconstructed in the K⁺K⁻ and π⁺π⁻ final states, where the final state particles have pseudorapidities between 2.5 and 4.5. The products of the cross sections and branching fractions are measured as σ x B(χ<sub>c0</sub> → K⁺K⁻) = 28.0 ± 2.8 ± 13.9 pb, σ x B(χ<sub>c0</sub> → π⁺π⁻) = 20.3 ± 2.4 ± 8.1 pb, σ x B(χ<sub>c2</sub> → K⁺K⁻) < 12.1 pb, σ x B(χ<sub>c2</sub> → π⁺π⁻) < 10.5 pb, where the first uncertainties are statistical and the second systematic, and limits are set at the 95% confidence level. A major source of systematic uncertainty is the determination of the fraction of the selected data which is CEP rather than inelastic backgrounds. Also described is HERSCHEL, a new subdetector installed at LHCb during the first long shutdown of the LHC. This is a system of forward shower counters which will provide CEP analyses with event-by-event rejection of inelastic backgrounds. The pseudorapidity coverage and detection efficiency of HERSCHEL are determined using Monte Carlo simulations. The pseudorapidity coverage extends to |η&| ≥ 10 due to the showering of collision products at the aperture limit. With a photoelectron threshold yield of 0.2 times the yield in the mean minimum bias event, the detection efficiency for single diffractive events is predicted to be 89% in the forward direction and 91% in the backward direction.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:686949 |
| Date | January 2015 |
| Creators | Stevenson, Scott Robert |
| Contributors | Wilkinson, Guy Roderick |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:4b59ed2b-308d-40b6-90ee-2415b0f2226b |
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