AbstractThe 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$$ \sqrt{s} $$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$$ {p}_{\mathrm{T}}^{\upmu \upmu} $$pTμμ. For ϒ(nS) mesons with$$ {p}_{\mathrm{T}}^{\upmu \upmu} $$pTμμ>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$$ {p}_{\mathrm{T}}^{\upmu \upmu} $$pTμμvalues for the ϒ(nS) states as a function of particle multiplicity are also measured and found to grow more steeply as their mass increases.
