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

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7 TeV
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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 |η|<1. Comparisons are made with previous measurements at s=09  TeV and 2.36 TeV. At s=7  TeV, for events with at least one charged particle in |η|<1, we obtain dNchd=601001(stat)+020012(syst). This corresponds to an increase of 576%04%(stat)+3618%(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.