Measurement of the Underlying Event Activity at the LHC with s√=7 TeV and Comparison with s√=0.9 TeV

Freya Blekman, Stijn Blyweert, Jorgen D'Hondt, Olivier Devroede, Rebeca Gonzalez Suarez, Alexis Kalogeropoulos, Michael Maes, Walter Van Doninck, Petra Van Mulders, Gerrit Van Onsem, Ilaria Villella

Research output: Contribution to journalArticlepeer-review

Abstract

A measurement of the underlying activity in scattering processes with a hard scale in the several GeV region is performed in proton-proton collisions at sqrt(s) = 0.9 and 7 TeV, using data collected by the CMS experiment at the LHC. The production of charged particles with pseudorapidity |eta| <2 and transverse momentum pT > 0.5 GeV/c is studied in the azimuthal region transverse to that of the leading set of charged particles forming a track-jet. A significant growth of the average multiplicity and scalar-pT sum of the particles in the transverse region is observed with increasing pT of the leading track-jet, followed by a much slower rise above a few GeV/c. For track-jet pT larger than a few GeV/c, the activity in the transverse region is approximately doubled with a centre-of-mass energy increase from 0.9 to 7 TeV. Predictions of several QCD-inspired models as implemented in PYTHIA are compared to the data.
Original languageEnglish
Article number109
Pages (from-to)1-27
Number of pages28
JournalJHEP
Volume2011
Issue number9
Publication statusPublished - 2011

Keywords

  • Hadron-hadron scattering
  • CMS

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