Jet and underlying event properties as a function of charged-particle multiplicity in proton-proton collisions at √s = 7 TeV


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

European Physical Journal C, vol.73, no.12, pp.1-26, 2013 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 73 Issue: 12
  • Publication Date: 2013
  • Doi Number: 10.1140/epjc/s10052-013-2674-5
  • Journal Name: European Physical Journal C
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.1-26
  • Yıldız Technical University Affiliated: Yes

Abstract

Characteristics of multi-particle production in proton-proton collisions at √s = 7 TeV are studied as a function of the charged-particle multiplicity, N ch. The produced particles are separated into two classes: those belonging to jets and those belonging to the underlying event. Charged particles are measured with pseudorapidity {pipe}η{pipe}<2.4 and transverse momentum p T>0.25 GeV/c. Jets are reconstructed from charged-particles only and required to have p T>5 GeV/c. The distributions of jet p T, average p T of charged particles belonging to the underlying event or to jets, jet rates, and jet shapes are presented as functions of N ch and compared to the predictions of the pythia and herwig event generators. Predictions without multi-parton interactions fail completely to describe the N ch-dependence observed in the data. For increasing N ch, pythia systematically predicts higher jet rates and harder p T spectra than seen in the data, whereas herwig shows the opposite trends. At the highest multiplicity, the data-model agreement is worse for most observables, indicating the need for further tuning and/or new model ingredients. © 2013 CERN for the benefit of the CMS collaboration.