Charged-particle multiplicity measurement in proton-proton collisions at $\sqrt{s}=7$ TeV with ALICE at LHC

The pseudorapidity density and multiplicity distribution of charged particles produced in proton-proton collisions at the LHC, at a centre-of-mass energy

\sqrt{s} = 7

TeV, were measured in the central pseudorapidity region |

\eta

| < 1. Comparisons are made with previous measurements at

\sqrt{s}

= 0.9 TeV and 2.36 TeV. At

\sqrt{s}

= 7 TeV, for events with at least one charged particle in |

\eta

| < 1, we obtain dNch/deta = 6.01

\pm

0.01 (stat.)

^{+0.20}_{-0.12}

(syst.). This corresponds to an increase of 57.6%

\pm

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.

Note:

12 pages, 3 captioned figures, 1 table, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/3904

charged particle: multiplicity
rapidity: density
multiplicity: spectrum
p p: inelastic scattering
CERN LHC Coll
ALICE
experimental results
energy dependence
7000 GeV-cms

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