, 2011:79,
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Date: 19 Jan 2011

Charged particle multiplicities in pp interactions at \( \sqrt {s} = 0.9 \) , 2.36, and 7 TeV


Measurements of primary charged hadron multiplicity distributions are presented for non-single-diffractive events in proton-proton collisions at centre-of-mass energies of \( \sqrt {s} = 0.9 \) , 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 \( \sqrt {s} = 0.9\;{\text{TeV}} \) is in agreement with previous measurements. At higher energies the increase of the mean multiplicity with \( \sqrt {s} \) 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.

Deceased (D. Lanske, V. Kaftanov, L. Tauscher, P. Schlein, B. C. Shen)
1: Also at CERN, European Organization for Nuclear Research, Geneva, Switzerland
2: Also at Universidade Federal do ABC, Santo Andre, Brazil
3: Also at Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France
4: Also at Suez Canal University, Suez, Egypt
5: Also at Fayoum University, El-Fayoum, Egypt
6: Also at Soltan Institute for Nuclear Studies, Warsaw, Poland
7: Also at Massachusetts Institute of Technology, Cambridge, USA
8: Also at Université de Haute-Alsace, Mulhouse, France
9: Also at Brandenburg University of Technology, Cottbus, Germany
10: Also at Moscow State University, Moscow, Russia
11: Also at Institute of Nuclear Research ATOMKI, Debrecen, Hungary
12: Also at Eötvös Lor´and University, Budapest, Hungary
13: Also at Tata Institute of Fundamental Research -HECR, Mumbai, India
14: Also at University of Visva-Bharati, Santiniketan, India
15: Also at Facolta’ Ingegneria Università di Roma “La Sapienza”, Roma, Italy
16: Also at Università della Basilicata, Potenza, Italy
17: Also at Laboratori Nazionali di Legnaro dell’ INFN, Legnaro, Italy
18: Also at California Institute of Technology, Pasadena, USA
19: Also at Faculty of Physics of University of Belgrade, Belgrade, Serbia
20: Also at University of California, Los Angeles, Los Angeles, USA
21: Also at University of Florida, Gainesville, USA
22: Also at Université de Genève, Geneva, Switzerland
23: Also at Scuola Normale e Sezione dell’ INFN, Pisa, Italy
24: Also at INFN Sezione di Roma; Università di Roma “La Sapienza”, Roma, Italy
25: Also at University of Athens, Athens, Greece
26: Also at The University of Kansas, Lawrence, USA
27: Also at Institute for Theoretical and Experimental Physics, Moscow, Russia
28: Also at Paul Scherrer Institut, Villigen, Switzerland
29: Also at University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade, Serbia
30: Also at Adiyaman University, Adiyaman, Turkey
31: Also at Mersin University, Mersin, Turkey
32: Also at Izmir Institute of Technology, Izmir, Turkey
33: Also at Kafkas University, Kars, Turkey
34: Also at Suleyman Demirel University, Isparta, Turkey
35: Also at Ege University, Izmir, Turkey
36: Also at Rutherford Appleton Laboratory, Didcot, United Kingdom
37: Also at INFN Sezione di Perugia; Università di Perugia, Perugia, Italy
38: Also at KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary
39: Also at Institute for Nuclear Research, Moscow, Russia
40: Also at Horia Hulubei National Institute of Physics and Nuclear Engineering (IFIN-HH), Bucharest, Romania
41: Also at Istanbul Technical University, Istanbul, Turkey