Charged-particle multiplicity measurement in proton-proton collisions at √s = 7 TeV with ALICE at LHC

摘要

The pseudorapidity density and multiplicity distribution of charged particles produced in proton-proton collisions at the LHC, at a centre-of-mass energy √s= 7 TeV, were measured in the central pseudorapidity region {pipe}η{pipe} < 1. Comparisons are made with previous measurements at √s = 0.9 TeV and 2.36 TeV. At √s = 7 TeV, for events with at least one charged particle in {pipe}η{pipe} < 1, we obtain dN_(ch)/dη = 6.01 ± 0.01(stat.)~(+0.20)_(-0.12)~((syst.)). This corresponds to an increase of 57.6% ± 0.4%(stat.)~(+3.6)_(-1.8)%(syst.) relative to collisions at 0.9 TeV, significantly higher than calculations from commonly used models. The multiplicity distribution at 7 TeV is described fairly well by the negative binomial distribution.