Measurement of the underlying event activity at the LHC with √s = 7 TeV and comparison with √s = 0:9 TeV


Chatrchyan S., Khachatryan V., Sirunyan A., Tumasyan A., Adam W., Bergauer T., ...More

Journal of High Energy Physics, vol.2011, no.9, 2011 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 2011 Issue: 9
  • Publication Date: 2011
  • Doi Number: 10.1007/jhep09(2011)109
  • Journal Name: Journal of High Energy Physics
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Keywords: Hadron-hadron scattering
  • Yıldız Technical University Affiliated: No

Abstract

A measurement of the underlying activity in events with a jet of transverse momentum in the several GeV region is performed in proton-proton collisions at √ s = 0:9 and 7TeV, using data collected by the CMS experiment at the LHC. The production of charged particles with pseudorapidity |η|<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 trackjet, 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 centreof- mass energy increase from 0:9 to 7TeV. Predictions of several QCD-inspired models as implemented in pythia are compared to the data.