Central exclusive production of Xc mesons in √s = 13 TeV proton-proton collisions

Thesis

A measurement is made of the central exclusive production of χ_c1 and χ_c2 mesons in proton-proton collisions at a centre-of-mass energy of √s = 13 TeV, using data collected by the LHCb experiment corresponding to a total single-interaction integrated luminosity of 711 pb^-1. The χ_c candidates are reconstructed through their radiative decay into J/ψγ , where we use photons that have converted into an electron pair, γ → e⁺e^-, and reconstruct the J/ψ through its dimuon final state. The High Rapidity Shower Counter sub-detector HeRSCheL is used to reduce inelastic background. The product of the cross section and the branching fractions, where the J/ψ muons are measured to be within the pseudorapidity region 2< η <4.5, are measured to be,

σ

(2<ηµ+µ− <4.5) χc1→J/ψ[µ+µ−]γ   = 19.5 ± 15.0(stat) ± 15.4(syst) pb [90% C.L.]

σ

(2<ηµ+µ− <4.5) χc2→J/ψ[µ+µ−]γ = 99.6 ± 12.7(stat) ± 27.7(syst) pb,

where the first uncertainty is statistical and the second is systematic. The product of the cross section and the branching fractions of χ_c1 mesons is quoted at a 90% confidence level (C.L.). These results are found to be in agreement with theoretical predictions.

Authors: Gruberg Cazon, BR

• DOI: 10.5287/ora-er2dyyko9
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: chic meson; LHCb; pomeron; central exclusive production; Forward rapidity counter; chic; LHC; Herschel; pomeron fusion; particle physics; HEP; low multiplicity; High energy physics; Higgs boson; chi_c; proton collision; double pomeron exchange; CERN; chi_c meson; HRC; CEP
• Subjects: Physics; CEP; double pomeron exchange; Detectors; Particle accelerators; central exclusive production; proton collision; pomeron fusion