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

par Sirunyan, A.M.;Beghin, Diego ;Bilin, Bugra ;Clerbaux, Barbara ;De Lentdecker, Gilles ;Delannoy, Hugo ;Dorney, Brian ;Favart, Laurent ;Grebenyuk, Anastasia ;Kalsi, Amandeep Kaur ;Malara, Andrea ;Moureaux, Louis ;Popov, Andrey ;Postiau, Nicolas ;Starling, Elizabeth Rose ;Thomas, Laurent ;Vander Velde, Catherine ;Vanlaer, Pascal ;Vannerom, David ; [et al.]
Référence The journal of high energy physics (Online), 2020, 11, 1
Publication Publié, 2020-11-01

Article révisé par les pairs

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Résumé :

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 pTμμ. For ϒ(nS) mesons with 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 pTμμ 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. [Figure not available: see fulltext.]