HEPData Search

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 |eta|<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 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.

5 data tables

Table 1

Average value of charged particle multiplicity per event and unit of pseudorapidity in the pseudorapidity range from -0.2 to 0.2.

Table 2

Charged particle multiplicity as a function of pseudorapidity.

Table 3

Charged particle multiplicity as a function of transverse momentum.

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INCLUSIVE PRODUCTION OF MESONS IN n p INTERACTIONS AT 3.83-GeV/c

INCLUSIVE PRODUCTION OF pi- MESONS IN n p INTERACTIONS AT P (n) = 1-GeV/c TO 5-GeV/c

PROPERTIES OF THE C Ta INTERACTIONS WITH LAMBDA HYPERON AND K0 MESON PRODUCTION AT 4.2-GeV/c PER NUCLEON

rivet Analysis
Charged-particle multiplicities in pp interactions at sqrt(s) = 900 GeV measured with the ATLAS detector at the LHC