Abstract
The production cross-section of the χc1(3872) state relative to the ψ(2S) meson is measured using proton-proton collision data collected with the LHCb experiment at centre-of-mass energies of sqrt{s} = 8 and 13 TeV, corresponding to integrated luminosities of 2.0 and 5.4 fb−1, respectively. The two mesons are reconstructed in the J/ψπ+π− final state. The ratios of the prompt and nonprompt χc1(3872) to ψ(2S) production cross-sections are measured as a function of transverse momentum, pT, and rapidity, y, of the χc1(3872) and ψ(2S) states, in the kinematic range 4 < pT< 20 GeV/c and 2.0 < y < 4.5. The prompt ratio is found to increase with pT, independently of y. For the prompt component, the double ratio of the χc1(3872) and ψ(2S) production cross-sections between 13 and 8 TeV is observed to be consistent with unity, independent of pT and centre-of-mass energy.
Highlights
Prompt-production cross-sections between χc1(3872) and ψ(2S) states produced directly from proton-proton collisions, as a function of multiplicity of the charged particles in an event, has been measured by the LHCb collaboration using 8 TeV pp collision data [18]
Production cross-section of the χc1(3872) state at a centre-of-mass energy of s = 7 TeV has been previously measured with 35 pb−1 of pp collision data [24]
The χc1(3872) and ψ(2S) candidates are both reconstructed in the J/ψπ+π− final state, with the J/ψ meson decaying into a pair of oppositely charged muons
Summary
The LHCb detector [25, 26] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks. The tracking system provides a measurement of the momentum, p, of charged particles with a relative uncertainty that varies from 0.5% at low momentum to 1.0% at 200 GeV/c. To avoid domination of the trigger CPU time by a few events with high occupancy, a set of global event requirements [31] is applied on the hit multiplicity of each sub-detector used by the pattern recognition algorithms. These requirements reject high-multiplicity events with a large number of pp interactions. The interaction of the generated particles with the detector, and its response, are implemented using the Geant toolkit [37, 38] as described in ref. [39]
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