CMS logoCMS event Hgg
Compact Muon Solenoid
LHC, CERN

CMS-FSQ-12-022 ; CERN-PH-EP-2013-195
Jet and underlying event properties as a function of charged-particle multiplicity in proton–proton collisions at $ \sqrt{s} $ = 7 TeV
Eur. Phys. J. C 73 (2013) 2674
Abstract: Characteristics of multi-particle production in proton-proton collisions at $ \sqrt{s} $ =7 TeV are studied as a function of the charged-particle multiplicity, Nch. 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 $ | \eta | < $ 2.4 and transverse momentum pT > 0.25 GeV/$c$. Jets are reconstructed from charged-particles only and required to have pT > 5 GeV/$c$. 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 Nch and compared to the predictions of the PYTHIA and HERWIG event generators. Predictions without multi-parton interactions fail completely to describe the Nch-dependence observed in the data. For increasing Nch, 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.
Figures CMS Publications
Figures

png pdf
Figure 1:

png pdf
Figure 2:

png pdf
Figure 3:

png pdf
Figure 4:

png pdf
Figure 5:

png pdf
Figure 6:

png pdf
Figure 7:

png pdf
Figure 8:

png pdf
Figure 9:

png pdf
Figure 10:

png pdf
Figure 11:

png pdf
Figure 12:

png pdf
Figure 13:

png pdf
Figure 14:

png pdf
Figure 15:

png pdf
Figure 16:

png pdf
Figure 17:

png pdf
Figure 18:
Compact Muon Solenoid
LHC, CERN