Return to search

A study of central exclusive production at LHCb

This thesis presents an analysis of the central exclusive production (CEP) of &chi;<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 &chi;<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 &sigma; x B(&chi;<sub>c0</sub> &rarr; K⁺K⁻) = 28.0 ± 2.8 ± 13.9 pb, &sigma; x B(&chi;<sub>c0</sub> &rarr; π⁺π⁻) = 20.3 ± 2.4 ± 8.1 pb, &sigma; x B(&chi;<sub>c2</sub> &rarr; K⁺K⁻) &LT; 12.1 pb, &sigma; x B(&chi;<sub>c2</sub> &rarr; π⁺π⁻) &LT; 10.5 pb, where the first uncertainties are statistical and the second systematic, and limits are set at the 95&percnt; 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 |&eta;&| &ge; 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&percnt; in the forward direction and 91&percnt; in the backward direction.

Identiferoai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:686949
Date January 2015
CreatorsStevenson, Scott Robert
ContributorsWilkinson, Guy Roderick
PublisherUniversity of Oxford
Source SetsEthos UK
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation
Sourcehttp://ora.ox.ac.uk/objects/uuid:4b59ed2b-308d-40b6-90ee-2415b0f2226b

Page generated in 0.0015 seconds