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Charged-particle multiplicities in ppinteractions measured with the ATLAS detector at the LHC

  • Author(s): Aad, G
  • Abbott, B
  • Abdallah, J
  • Abdelalim, AA
  • Abdesselam, A
  • Abdinov, O
  • Abi, B
  • Abolins, M
  • Abramowicz, H
  • Abreu, H
  • Acerbi, E
  • Acharya, BS
  • Ackers, M
  • Adams, DL
  • Addy, TN
  • Adelman, J
  • Aderholz, M
  • Adomeit, S
  • Adragna, P
  • Adye, T
  • Aefsky, S
  • Aguilar-Saavedra, JA
  • Aharrouche, M
  • Ahlen, SP
  • Ahles, F
  • Ahmad, A
  • Ahsan, M
  • Aielli, G
  • Akdogan, T
  • Åkesson, TPA
  • Akimoto, G
  • Akimov, AV
  • Alam, MS
  • Alam, MA
  • Albrand, S
  • Aleksa, M
  • Aleksandrov, IN
  • Aleppo, M
  • Alessandria, F
  • Alexa, C
  • Alexander, G
  • Alexandre, G
  • Alexopoulos, T
  • Alhroob, M
  • Aliev, M
  • Alimonti, G
  • Alison, J
  • Aliyev, M
  • Allport, PP
  • Allwood-Spiers, SE
  • Almond, J
  • Aloisio, A
  • Alon, R
  • Alonso, A
  • Alonso, J
  • Alviggi, MG
  • Amako, K
  • Amaral, P
  • Amelung, C
  • Ammosov, VV
  • Amorim, A
  • Amorós, G
  • Amram, N
  • Anastopoulos, C
  • Andeen, T
  • Anders, CF
  • Anderson, KJ
  • Andreazza, A
  • Andrei, V
  • Andrieux, ML
  • Anduaga, XS
  • Angerami, A
  • Anghinolfi, F
  • Anjos, N
  • Annovi, A
  • Antonaki, A
  • Antonelli, M
  • Antonelli, S
  • Antos, J
  • Anulli, F
  • Aoun, S
  • Aperio Bella, L
  • Apolle, R
  • Arabidze, G
  • Aracena, I
  • Arai, Y
  • Arce, ATH
  • Archambault, JP
  • Arfaoui, S
  • Arguin, JF
  • Arik, E
  • Arik, M
  • Armbruster, AJ
  • Arms, KE
  • Armstrong, SR
  • Arnaez, O
  • Arnault, C
  • Artamonov, A
  • Artoni, G
  • Arutinov, D
  • et al.
Abstract

Measurements are presented from proton-proton collisions at centre-of-mass energies of s = 0.9, 2.36 and 7 TeV recorded with the ATLAS detector at the LHC. Events were collected using a single-arm minimumbias trigger. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the relationship between the mean transverse momentum and charged-particle multiplicity are measured. Measurements in different regions of phase space are shown, providing diffraction-reduced measurements as well as more inclusive ones. The observed distributions are corrected to well-defined phase-space regions, using model-independent corrections. The results are compared to each other and to various Monte Carlo (MC) models, including a new AMBT1 pythia6 tune. In all the kinematic regions considered, the particle multiplicities are higher than predicted by the MC models. The central charged-particle multiplicity per event and unit of pseudorapidity, for tracks with pT < 100 MeV, is measured to be 3.483±0.009 (stat)±0.106 (syst) at s = 0.9 TeV and 5.630±0.003 (stat)±0.169 (syst) at s = 7 TeV. © 2011 CERN for the benefit of the ATLAS Collaboration, published under licence by IOP Publishing Ltd for the Institute of Physics and Deutsche Physikalische Gesellschaft.

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