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Investigation into the event-activity dependence of Υ(nS) relative production in proton-proton collisions at √s = 7 TeV

The ratios of the production cross sections between the excited Υ(2S) and Υ(3S) mesons and the Υ(1S) ground state, detected via their decay into two muons, are studied as a function of the number of charged particles in the event. The data are from proton-proton collisions at s√= 7 TeV, corresponding to an integrated luminosity of 4.8 fb−1, collected with the CMS detector at the LHC. Evidence of a decrease in these ratios as a function of the particle multiplicity is observed, more pronounced at low transverse momentum pμμT. For Υ(nS) mesons with pμμT > 7 GeV, where most of the data were collected, the correlation with multiplicity is studied as a function of the underlying event transverse sphericity and the number of particles in a cone around the Υ(nS) direction. The ratios are found to be multiplicity independent for jet-like events. The mean pμμT values for the Υ(nS) states as a function of particle multiplicity are also measured and found to grow more steeply as their mass increases.

High energy physics ; Experimental particle physics ; LHC ; CMS ; Particle Physics Experiments ; Physics ; Vector boson scattering ; Hadron-Hadron scattering (experiments) ; Supersymmetry ; Higgs physics ; Particle and resonance production ; B physics ; Particle correlations and fluctuations ; Quarkonium

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