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Title: Jet and underlying event properties as a function of charged-particle multiplicity in proton-proton collisions at sqrt(s) = 7 TeV

Characteristics of multi-particle production in proton-proton collisions at sqrt(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 abs(eta) < 2.4 and transverse momentum pt > 0.25 GeV. Jets are reconstructed from charged-particles only and required to have pt > 5 GeV. The distributions of jet pt, average pt 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 pt 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.
Publication Date:
OSTI Identifier:
Report Number(s):
FERMILAB-PUB-13-627-CMS; CMS-FSQ-12-022; CERN-PH-EP-2013-195
Journal ID: ISSN 1434-6044; ArticleNumber: 2674; arXiv: 1310.4554
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: European Physical Journal. C, Particles and Fields; Journal Volume: 73; Journal Issue: 12
Research Org:
Fermi National Accelerator Laboratory (FNAL), Batavia, IL
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Contributing Orgs:
CMS Collaboration
Country of Publication:
United States
High Energy Physics; HEP; hep-ex