TOP-12-028 Measurement of the differential top-quark pair production cross section in the dilepton channel at 8 TeV

Abstract

Normalised differential top-quark pair production cross sections are measured in pp collisions at a centre-of-mass energy of 8 TeV at the LHC with the CMS detector using data recorded in 2012 corresponding to an integrated luminosity of 12.2 fb−1 . The measurements are performed in the dilepton decay channels (e+ e− , μ+ μ− , and μ e ). The ttbar production cross section is measured as a function of kinematic properties of the final-state charged leptons and jets associated to b quarks, as well as those of the top quarks and the ttbar system. The data are compared with several predictions from perturbative QCD calculations up to approximate next-to-next-to-leading-order precision. No significant deviations from the standard model are observed.

Public Document

The document CMS-PAS-TOP-12-028 can be found here.

Public Supplemental material

For additional public material ("pseudo-top" framework) click here

Figures

Basic kinematic distributions after event selection

Figure Caption
HypBjetMulti_noBTag.pngHypjetMulti.png HypLeptonpTLead.pngHypBJetpTLead.png Kinematic distributions after event selection for the dilepton channels: multiplicity of the reconstructed b-tagged jets, multiplicity of the reconstructed jets, the pT of the highest pT (leading) isolated leptons and the pT of the leading b jet. Both pT distributions are shown after the b-tagging requirement. The normalisation of the Z/γ∗ +jets background is determined from data. Links to the PDF versions: B-jet multiplicity, Jet multiplicity, Leading lepton pT, Leading b-jet pT.
HypToppTLead.pngHypTTBarpT.png HypTopRapidityLead.pngHypTTBarRapidity.png Distribution of the leading top quark and of ttbar quantities as obtained from the kinematic reconstruction. The top row shows the transverse momenta, and the bottom row shows the rapidities. The normalization of the Z/γ∗ +jets background is determined from data. Links to the PDF versions : Leading top pT, ttbar pT, Leading lepton y, ttbar y.

Normalized differential cross sections

Figure Caption
DiffXS_HypLeptonpTLead.pngDiffXS_HypLeptonpTNLead.png DiffXS_HypLeptonEtaLead.pngDiffXS_HypLeptonEtaNLead.png Normalised differential ttbar production cross section as a function of the pT and η of the leading and next-to-leading lepton presented at the particle level and in the visible phase space. The superscript ‘l’ refers to both lepton and antilepton. The inner (outer) error bars indicate the statistical (combined statistical and systematic) uncertainty. The measurement is compared to predictions from MadGraph, POWHEG, and MC@NLO Monte Carlo generators. The MadGraph prediction is shown both as a curve and as a binned histogram. Links to the PDF versions: Leading lepton pT, Next-to-leading lepton pT, Leading lepton eta, Next-to-leading lepton eta.
DiffXS_HypLLBarpT.pngDiffXS_HypLLBarMass.png Normalised differential ttbar production cross section as a function of the pT and the mass of the lepton pair presented at the particle level and in the visible phase space. The inner (outer) error bars indicate the statistical (combined statistical and systematic) uncertainty. The measurement is compared to predictions from MadGraph, POWHEG, and MC@NLO Monte Carlo generators. The MadGraph prediction is shown both as a curve and as a binned histogram. Links to the PDF versions: Lepton pair pT, Lepton pair mass.
DiffXS_HypBJetpTLead.png DiffXS_HypBJetpTNLead.pngDiffXS_HypBJetEtaLead.pngDiffXS_HypBJetEtaNLead.png Normalised differential ttbar production cross section as a function of the pT and eta of the leading and next-to-leading b jet, and the invariant mass of the lepton and b-jet, presented at the particle level and in the visible phase space. The superscript ‘b’ refers to both b and bbar-jets. The inner (outer) error bars indicate the statistical (combined statistical and systematic) uncertainty. The measurement is compared to predictions from MadGraph, POWHEG, and MC@NLO Monte Carlo generators. The MadGraph prediction is shown both as a curve and as a binned histogram. Links to the PDF versions: Leading b-jet pT, Next-to-leading b-jet pT, Leading b-jet eta, Next-to-leading b-jet eta.
DiffXS_HypLeptonBjetMass.png Normalised differential ttbar production cross section as a function of the invariant mass of the lepton and b-jet presented at the particle level and in the visible phase space. The superscript ‘b’ refers to both b and bbar-jets. The inner (outer) error bars indicate the statistical (combined statistical and systematic) uncertainty. The measurement is compared to predictions from MadGraph, POWHEG, and MC@NLO Monte Carlo generators. Link to the PDF version: Lepton-b-jet mass
DiffXS_HypToppTLead.pngDiffXS_HypToppTNLead.png DiffXS_HypTopRapidityLead.pngDiffXS_HypTopRapidityNLead.png Normalised differential ttbar production cross section as a function of the pT and rapidity of the leading and next-to-leading top quarks or antiquarks presented at the parton level and extrapolated to the full phase space. The superscript 't' refers to both top quarks and antiquarks. The inner (outer) error bars indicate the statistical (combined statistical and systematic) uncertainty. The measurement is compared to predictions from MadGraph, POWHEG, and MC@NLO Monte Carlo generators. The MadGraph prediction is shown both as a curve and as a binned histogram. Links to the PDF versions: Leading top pT, Next-to-leading top pT, Leading top rapidity, Next-to-leading top rapidity.
DiffXS_HypToppT.pngDiffXS_HypTopRapidity.png DiffXS_HypTTBarpT.pngDiffXS_HypTTBarMass.png DiffXS_HypTTBarRapidity.png Normalised differential ttbar production cross section as a function of the pT and rapidity of the top quarks or antiquarks, the pT, mass and rapidity of the top-quark pairs presented at the parton level and extrapolated to the full phase space. The inner (outer) error bars indicate the statistical (combined statistical and systematic) uncertainty. The measurement is compared to predictions from MadGraph, POWHEG, and MC@NLO Monte Carlo generators, and to an approximate NNLO calculation where available. The MadGraph prediction is shown both as a curve and as a binned histogram. Links to the PDF versions: Top pT, Top rapidity, ttbar pT, ttbar mass, ttbar rapidity.
Topic attachments
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PDFpdf DiffXS_HypBJetEtaLead.pdf r1 manage 6.5 K 2013-02-26 - 16:51 CarmenDiezPardos  
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Topic revision: r5 - 2014-03-11 - AndreasMeyer
 
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