Charged particle correlations in \bar pp$$ collisions at c.m. energies of 200, 546 and 900 GeV (original) (raw)
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The multiplicity dependence of the pseudorapidity density of charged particles in proton-proton (pp) collisions at centre-of-mass energies sqrts\sqrt{s}sqrts = 5.02, 7 and 13 TeV measured by ALICE is reported. The analysis relies on track segments measured in the midrapidity range ($|\eta| 0}$). The multiplicity dependence of the pseudorapidy density of charged particles is measured with mid and forward rapidity multiplicity estimators, the latter being less affected by autocorrelations. A detailed comparison with predictions from the PYTHIA 8 and EPOS LHC event generators is also presented. Both generators provide a good description of the data.
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We present the first direct measurements of charged-particle multiplicity distributions for pp collisions at ISR energies. The measurements are performed by means of a streamer chamber detector with large solid-angle coverage and excellent multitrack efficiency. Particle densities are observed to rise in the central region as x/s increases. The multiplicity distributions in this region deviate from a Poisson law, thus giving evidence for correlations. These correlations are of the same type as those obtained from clustering of the collision products. The mean charged multiplicity over the full rapidity range increases faster than log s. Our data do not support an early onset of KNO multiplicity scaling.
The European Physical …, 2010
Charged-particle production was studied in proton-proton collisions collected at the LHC with the ALICE detector at centre-of-mass energies 0.9 TeV and 2.36 TeV in the pseudorapidity range |η| < 1.4. In the central region (|η| < 0.5), at 0.9 TeV, we measure charged-particle pseudorapidity density dN ch /dη = 3.02 ± 0.01(stat.) +0.08 −0.05 (syst.) for inelastic interactions, and dN ch /dη = 3.58 ± 0.01(stat.) +0.12 −0.12 (syst.) for nonsingle-diffractive interactions. At 2.36 TeV, we find dN ch /dη = 3.77 ± 0.01(stat.) +0.25 −0.12 (syst.) for inelastic, and dN ch /dη = 4.43 ± 0.01(stat.) +0.17 −0.12 (syst.) for non-single-diffractive collisions. The relative increase in charged-particle multiplicity from the lower to higher energy is 24.7%±0.5%(stat.) +5.7 −2.8 %(syst.) for inelastic and 23.7% ± 0.5%(stat.) +4.6 −1.1 %(syst.) for non-single-diffractive interactions. This increase is consistent with that reported by the CMS collaboration for non-single-diffractive events and larger than that found by a number of commonly used models. The multiplicity distribution was measured in different pseudorapidity intervals and studied in terms of KNO variables at both energies. The results are compared to protonantiproton data and to model predictions. 6
Charged particle multiplicities in pp interactions at sqrt(s) = 0.9, 2.36, and 7 TeV
CITATIONS 35 READS 166 3046 authors, including: Some of the authors of this publication are also working on these related projects: GRAPHENE FLAGSHIP EU FP7 project FP7-604391, work package 4 High frequency electronics View project Physics at the LHC with the ATLAS detector View project Adrien Renaud 484 PUBLICATIONS 3,905 CITATIONS SEE PROFILE
Charged particle multiplicities in pp interactions at , 2.36, and 7 TeV
Journal of High Energy Physics, 2011
Measurements of primary charged hadron multiplicity distributions are presented for non-single-diffractive events in proton-proton collisions at centre-of-mass energies of \( \sqrt {s} = 0.9 \) , 2.36, and 7 TeV, in five pseudorapidity ranges from |η| .5 to |η| .4. The data were collected with the minimum-bias trigger of the CMS experiment during the LHC commissioning runs in 2009 and the 7 TeV run in 2010. The multiplicity distribution at \( \sqrt {s} = 0.9\;{\text{TeV}} \) is in agreement with previous measurements. At higher energies the increase of the mean multiplicity with \( \sqrt {s} \) is underestimated by most event generators. The average transverse momentum as a function of the multiplicity is also presented. The measurement of higher-order moments of the multiplicity distribution confirms the violation of Koba-Nielsen-Olesen scaling that has been observed at lower energies.
2010
Charged-particle production was studied in proton-proton collisions collected at the LHC with the ALICE detector at centre-of-mass energies 0.9 TeV and 2.36 TeV in the pseudorapidity range |η| < 1.4. In the central region (|η| < 0.5), at 0.9 TeV, we measure charged-particle pseudorapidity density dN ch /dη = 3.02 ± 0.01(stat.) +0.08 −0.05 (syst.) for inelastic interactions, and dN ch /dη = 3.58 ± 0.01(stat.) +0.12 −0.12 (syst.) for nonsingle-diffractive interactions. At 2.36 TeV, we find dN ch /dη = 3.77 ± 0.01(stat.) +0.25 −0.12 (syst.) for inelastic, and dN ch /dη = 4.43 ± 0.01(stat.) +0.17 −0.12 (syst.) for non-single-diffractive collisions. The relative increase in charged-particle multiplicity from the lower to higher energy is 24.7%±0.5%(stat.) +5.7 −2.8 %(syst.) for inelastic and 23.7% ± 0.5%(stat.) +4.6 −1.1 %(syst.) for non-single-diffractive interactions. This increase is consistent with that reported by the CMS collaboration for non-single-diffractive events and larger than that found by a number of commonly used models. The multiplicity distribution was measured in different pseudorapidity intervals and studied in terms of KNO variables at both energies. The results are compared to protonantiproton data and to model predictions. 6