Charged-particle multiplicities in pp interactions at root s=900 GeV measured with the ATLAS detector at the LHC ATLAS Collaboration


Aad G., Abat E., Abbott B., Abdallah J., Abdelalim A. A. , Abdesselam A., ...More

PHYSICS LETTERS B, vol.688, no.1, pp.21-42, 2010 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 688 Issue: 1
  • Publication Date: 2010
  • Doi Number: 10.1016/j.physletb.2010.03.064
  • Title of Journal : PHYSICS LETTERS B
  • Page Numbers: pp.21-42
  • Keywords: Charged-particle, Multiplicities, 900 GeV, ATLAS, LHC, Minimum bias, TRANSVERSE-MOMENTUM SPECTRA, SQUARE-ROOT-S, CM ENERGIES, DISTRIBUTIONS, COLLISIONS, MASS

Abstract

The first measurements from proton-proton collisions recorded with the ATLAS detector at the LHC are presented. Data were collected in December 2009 using a minimum-bias trigger during collisions at a centre-of-mass energy of 900 GeV. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity, and the relationship between mean transverse momentum and charged-particle multiplicity are measured for events with at least one charged particle in the kinematic range vertical bar eta vertical bar < 2.5 and p(T) > 500 MeV. The measurements are compared to Monte Carlo models of proton-proton collisions and to results from other experiments at the same centre-of-mass energy. The charged-particle multiplicity per event and unit of pseudorapidity eta = 0 is measured to be 1.333 +/- 0.003(stat.) +/- 0.040(syst.), which is 5-15% higher than the Monte Carlo models predict. 2010 Published by Elsevier B.V.