Charged particle multiplicities in pp interactions at (raiz de) s = 0:9, 2:36, and 7 TeV

38 páginas, 7 figuras, 4 tablas.-- Open Access: This article is distributed under the terms of the Creative Commons Attribution Noncommercial License.Measurements of primary charged hadron multiplicity distributions are presented for non-single-di ractive events in proton-proton collisions at centre-of-mass energies of ps = 0:9, 2.36, and 7TeV, in ve pseudorapidity ranges from j j < 0:5 to j j < 2:4. The data were collected with the minimum-bias trigger of the CMS experiment during the LHC commissioning runs in 2009 and the 7TeV run in 2010. The multiplicity distribution at ps = 0:9TeV is in agreement with previous measurements. At higher energies the increase of the mean multiplicity with ps is underestimated by most event generators. The average transverse momentum as a function of the multiplicity is also presented. The measurement of higher-order moments of the multiplicity distribution con rms the violation of Koba-Nielsen-Olesen scaling that has been observed at lower energies.Individuals have received support from the Marie-Curie programme and the European Research Council (European Union); the Leventis Foundation; the A. P. Sloan Foundation; the Alexander von Humboldt Foundation; the Associazione per lo Sviluppo Scienti co e Tecnologico del Piemonte (Italy); the Belgian Federal Science Policy Office; the Fonds pour la Formation à la Recherche dans l'industrie et dans l'Ágriculture (FRIA-Belgium); and the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium).Peer reviewe