Charged-particle multiplicities in pp interactions at root s=900 GeV measured with the ATLAS detector at the LHC ATLAS Collaboration
Academic Article
Overview
Research
Identity
Additional Document Info
View All
Overview
abstract
CERN, for the benefit of the ATLAS Collaboration. 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 chargedparticle multiplicity are measured for events with at least one charged particle in the kinematic range || < 2.5 and pT > 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 at = 0 is measured to be 1.333 0.003(stat.) 0.040(syst.), which is 5-15% higher than the Monte Carlo models predict.