TOP-12-023
Measurement of jet multiplicity in di-leptonic top pair events

Abstract

Jet multiplicity distributions are measured in pp-collisions at sqrt{s} = 7 TeV with the CMS detector using a dataset recorded in 2011 corresponding to an integrated luminosity of 5.0 fb-1.The measurement is performed in the dileptonic decay channels (m+m-, e+e- and m+/- e-/+) of the top-antitop quark pairs, with at least two isolated leptons and at least one b-jet in the final state. The differential top anti-top quark cross section is measured as a function of the jet multiplicity. Furthermore, the distribution of the fraction of events without additional jets above a threshold is measured as functions of the jet transverse momentum and of the scalar sum of the transverse momenta of all additional jets. Several QCD calculations are compared with the data.

Figures

Jet multiplicity and kinematic distributions of the additional jets after event selection

Figure Caption
HypJetMult.png Reconstructed jet multiplicity distribution in the event after event selection for all jets with transverse momenta of at least 30~GeV. The ttbar sample is simulated using MADGRAPH. "ttbar signal" refers to the events decaying dileptonically, "ttbar other" refers to the rest of the decay modes, including \ttbar decays intro prompt tau-leptons. The hatched area represents the uncertainty on the predicted \ttbar\ cross section and the luminosity. [Get pdf version]
HypJetMultpt60.png Reconstructed jet multiplicity distribution in the event after event selection for all jets with transverse momenta of at least 60 GeV. The \ttbar\ sample is simulated using \MADGRAPH. "\ttbar signal" refers to the events decaying dileptonically, "\ttbar other" refers to the rest of the decay modes, including \ttbar decays intro prompt $\tau$-leptons. The hatched area represents the uncertainty on the predicted \ttbar\ cross section and the luminosity. Notice that the event selection requires two jets with pt>30~GeV. [Get pdf version]
HypExtraJetpT.png Distribution of the transverse momentum of the first leading additional reconstructed jets compared to signal and background simulated samples. The hatched area represents the uncertainty on the predicted \ttbar\ cross section and the luminosity. [Get pdf version]
HypExtraJetEta.png Distribution of eta of the first leading additional reconstructed jets compared to signal and background simulated samples. The hatched area represents the uncertainty on the predicted \ttbar\ cross section and the luminosity. [Get pdf version]
HypExtraJetpT2.png Distribution of the transverse momentum of the second leading additional reconstructed jets compared to signal and background simulated samples. The hatched area represents the uncertainty on the predicted \ttbar\ cross section and the luminosity. [Get pdf version]
HypExtraJetEta2.png Distribution of eta of the second leading additional reconstructed jets compared to signal and background simulated samples. The hatched area represents the uncertainty on the predicted \ttbar\ cross section and the luminosity. [Get pdf version]

Normalised differential cross sections as a function of jet multiplicity

Figure Caption
DiffXS_HypJetMultPow.png Normalised differential cross-section as a function of jet multiplicity for jets with pT>30GeV. The data are compared with predictions from MADGRAPH+Pythia, MCATNLO+Herwig and POWHEG+Pythia. The errors on the data points indicate the statistical (inner bars) and the total uncertainty. [Get pdf version]
DiffXS_HypJetMultMadgraph.png Normalised differential cross-section as a function of jet multiplicity for jets with pT>30GeV. The figures show the behaviour of MADGRAPH generator when varying the $Q^2$ and matching scales. The errors on the data points indicate the statistical (inner bars) and the total uncertainty. [Get pdf version]
DiffXS_HypJetMultpt60Pow.png Normalised differential cross-section as a function of jet multiplicity for jets with pT>60GeV. The data are compared with predictions from MADGRAPH+Pythia, MCATNLO+Herwig and POWHEG+Pythia. The errors on the data points indicate the statistical (inner bars) and the total uncertainty. [Get pdf version]
DiffXS_HypJetMultpt60Madgraph.png Normalised differential cross-section as a function of jet multiplicity for jets with pT>60GeV. The figures show the behaviour of MADGRAPH generator when varying the $Q^2$ and matching scales. The errors on the data points indicate the statistical (inner bars) and the total uncertainty. [Get pdf version]

"Gap fraction"

Figure Caption
GapFracpt_finalPow.png Measured gap fraction as a function of the additional jet pt. Data are compared to predictions from MADGRAPH+Pythia, POWHEG+Pythia and MC@NLO+Herwig. The errors on the data points indicate the statistical uncertainty. The shaded band corresponds to the statistical and systematic uncertainties (background contamination, PU, b-tagging, JES, JER, unfolding) added in quadrature. [Get pdf version]
GapFracpt_finalMadgraph.png Measured gap fraction as a function of the additional jet pt. Data are compared to predictions from MADGRAPH+Pythia and MADGRAPH with varied Q2 and jet-parton matching scales. The errors on the data points indicate the statistical uncertainty. The shaded band corresponds to the statistical and systematic uncertainties (background contamination, PU, b-tagging, JES, JER, unfolding) added in quadrature. [Get pdf version]
GapFracHT_finalPow.png Measured gap fraction as a function of the scalar sum of the pt of the additional jets. Data are compared to predictions from MADGRAPH+Pythia, POWHEG+Pythia and MC@NLO+Herwig. The shaded band corresponds to the statistical and systematic uncertainties (background contamination, PU, b-tagging, JES, JER, unfolding) added in quadrature.[Get pdf version]
GapFracHT_finalMadgraph.png Measured gap fraction as a function of the scalar sum of the pt of the additional jets. Data are compared to predictions from the nominal MADGRAPH+Pythia and to MADGRAPH with varied Q2 and jet-parton matching scales. The errors on the data points indicate the statistical uncertainty. The shaded band corresponds to the statistical and systematic uncertainties (background contamination, PU, b-tagging, JES, JER, unfolding) added in quadrature. [Get pdf version]

Public Supplemental material

For additional public material click here

-- CarmenDiezPardos - 14-Sep-2012

Topic attachments
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PDFpdf DiffXS_HypJetMultMadgraph.pdf r1 manage 16.5 K 2012-09-14 - 19:19 CarmenDiezPardos  
PNGpng DiffXS_HypJetMultMadgraph.png r1 manage 16.5 K 2012-09-14 - 19:19 CarmenDiezPardos  
PDFpdf DiffXS_HypJetMultPow.pdf r1 manage 16.2 K 2012-09-14 - 19:19 CarmenDiezPardos  
PNGpng DiffXS_HypJetMultPow.png r1 manage 14.4 K 2012-09-14 - 19:19 CarmenDiezPardos  
PDFpdf DiffXS_HypJetMultpt60Madgraph.pdf r1 manage 17.0 K 2012-09-14 - 19:19 CarmenDiezPardos  
PNGpng DiffXS_HypJetMultpt60Madgraph.png r1 manage 17.5 K 2012-09-14 - 19:19 CarmenDiezPardos  
PDFpdf DiffXS_HypJetMultpt60Pow.pdf r1 manage 16.7 K 2012-09-14 - 19:19 CarmenDiezPardos  
PNGpng DiffXS_HypJetMultpt60Pow.png r1 manage 15.3 K 2012-09-14 - 19:19 CarmenDiezPardos  
PDFpdf GapFracHT_finalMadgraph.pdf r1 manage 21.5 K 2012-09-14 - 10:19 CarmenDiezPardos  
PNGpng GapFracHT_finalMadgraph.png r2 r1 manage 88.1 K 2012-09-14 - 20:19 CarmenDiezPardos  
PDFpdf GapFracHT_finalPow.pdf r1 manage 20.3 K 2012-09-14 - 10:19 CarmenDiezPardos  
PNGpng GapFracHT_finalPow.png r2 r1 manage 86.7 K 2012-09-14 - 20:19 CarmenDiezPardos  
PDFpdf GapFracpt_finalMadgraph.pdf r1 manage 21.5 K 2012-09-14 - 09:50 CarmenDiezPardos  
PNGpng GapFracpt_finalMadgraph.png r2 r1 manage 98.2 K 2012-09-14 - 20:19 CarmenDiezPardos  
PDFpdf GapFracpt_finalPow.pdf r1 manage 20.3 K 2012-09-14 - 09:50 CarmenDiezPardos  
PNGpng GapFracpt_finalPow.png r2 r1 manage 85.8 K 2012-09-14 - 20:19 CarmenDiezPardos  
PDFpdf HypExtraJetEta.pdf r1 manage 24.7 K 2012-09-14 - 10:42 CarmenDiezPardos  
PNGpng HypExtraJetEta.png r2 r1 manage 22.6 K 2012-09-14 - 20:16 CarmenDiezPardos  
PDFpdf HypExtraJetEta2.pdf r1 manage 19.3 K 2012-09-14 - 10:42 CarmenDiezPardos  
PNGpng HypExtraJetEta2.png r2 r1 manage 20.1 K 2012-09-14 - 20:16 CarmenDiezPardos  
PDFpdf HypExtraJetpT.pdf r1 manage 25.7 K 2012-09-14 - 10:42 CarmenDiezPardos  
PNGpng HypExtraJetpT.png r2 r1 manage 22.0 K 2012-09-14 - 20:19 CarmenDiezPardos  
PDFpdf HypExtraJetpT2.pdf r1 manage 22.7 K 2012-09-14 - 10:42 CarmenDiezPardos  
PNGpng HypExtraJetpT2.png r2 r1 manage 20.5 K 2012-09-14 - 20:16 CarmenDiezPardos  
PDFpdf HypJetMult.pdf r1 manage 18.0 K 2012-09-14 - 12:27 CarmenDiezPardos  
PNGpng HypJetMult.png r2 r1 manage 18.5 K 2012-09-14 - 20:16 CarmenDiezPardos  
PDFpdf HypJetMultpt60.pdf r1 manage 17.9 K 2012-09-14 - 12:27 CarmenDiezPardos  
PNGpng HypJetMultpt60.png r2 r1 manage 18.5 K 2012-09-14 - 20:16 CarmenDiezPardos  
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Topic revision: r8 - 2013-04-11 - RobertoTenchini
 
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