Charged particle multiplicities in pp interactions at $ \sqrt {s} = 0.9 $ , 2.36, and 7 TeV
V. Khachatryana b, A. M. Sirunyana b, A. Tumasyanb c, W. Adama d, T. Bergauera d, M. Dragicevicc d, J. Eröc d, Christian W. Fabjanc d, M. Friedld e, Rudolf Konrad Fruhwirthd e, V. M. Hammerd, J. Hammera b, S. Hänselc d, C. Hartlc d, Michael J. R. Hochd e, N. Hörmannd e, J. Hrubecd e, M. Jeitlera d, Gregor Kasieczkaa d, W. Kiesenhoferc d, M. Krammerd e, Dietrich Likod e, I. Mikulecd e, M. Pernickad e, H. Rohringerd f, R. Schöfbeckd f, J. Straussd e, A. Taurokd e, F. A. Teischingerd e, W. Waltenbergerd e and 2123 others
- aYerevan Physics Institute , Yerevan , Armenia
- bYerevan Physics Institute, Yerevan, Armenia
- cInstitut für Hochenergiephysik der OeAW , Wien , Austria
- dInstitut für Hochenergiephysik der OeAW, Wien, Austria
- eNational Centre for Particle and High Energy Physics , Minsk , Belarus
- fUniversiteit Antwerpen , Antwerpen , Belgium
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Abstract
Measurements of primary charged hadron multiplicity distributions are presented for non-single-diffractive events in proton-proton collisions at centre-of-mass energies of √ s = 0.9, 2.36, and 7 TeV, in five pseudorapidity ranges from |η| < 0.5 to |η| < 2.4.The data were collected with the minimum-bias trigger of the CMS experiment during the LHC commissioning runs in 2009 and the 7 TeV run in 2010.The multiplicity distribution at √ s = 0.9 TeV is in agreement with previous measurements.At higher energies the increase of the mean multiplicity with √ s 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 confirms the violation of Koba-Nielsen-Olesen scaling that has been observed at lower energies.