Top quark pair differential cross sections in ATLAS and CMS

Introduction

The top quark pair cross section has been measured differentially as a function of a large number of kinematic distributions of top quarks, top quark pairs, leptons, and b jets in the ATLAS and CMS collaborations, both at 7 and 8 TeV. The data are compared with several predictions from perturbative QCD up to approximate NNLO precision. The goal is to compare the respective measurements in ATLAS and CMS and understand possible differences in the analysis procedure and/or the results towards a possible future combination. First steps towards this comparison are taken based on 7 TeV results in the l+jets channels and focusing on the following distributions: pT(top), m(ttbar), pT(ttbar), y(ttbar).

List of items for ATLAS-CMS comparison


Starting list of points to be addressed by the two experiments for comparison of the results.

First study: consistency of the definition of the top quark at parton level and the MC samples at generator level used in ATLAS and CMS

MC ttbar samples: parameters and tunes

ATLAS settings

  • POWHEG+PYTHIA: POWHEG is POWHEG-hvq (1, 2 3) (patch4); it uses NLO QCD matrix elements with NLO CT10 parton distribution function (PDF) and it is interfaced to PYTHIA6 with the Perugia 2011C tune.

  • POWHEG+HERWIG: POWHEG is POWHEG-hvq (1, 2 3) (patch4); it uses NLO QCD matrix element with with NLO CT10 PDF and it is interfaced to HERWIG (v6.520) to model parton showering and hadronization and JIMMY (V.4.31) for modelling multiple interaction. Underlying event tune was AUET2.

  • ALPGEN+HERWIG : Events with up to 5 additional partons are generated using ALPGEN (v2.13) with LO CTEQ6L1 PDF. HERWIG (v6.520) is used for parton showering and hadronization and JIMMY (V.4.31) is used for the modelling of multiple interactions. Underlying event tune is AUET2.

  • MC@NLO+HERWIG : MC@NLO (V4.01) uses NLO QCD matrix element withNLO CT10 PDF and it is interfaced to HERWIG (v6.520) to model parton showering and hadronization and JIMMY(V.4.31) for modelling multiple interaction. Underlying event tune is AUET2.

Figures

Figure Caption
treeATLASCMScomparisonCMSonlyFineBinningtopPt.png The distribution of the transverse momentum, pT, of the top quark in ttbar events at the generator (parton) level is shown for all CMS samples used in the ttbar differential cross section analyses. The lower part of the figure shows the ratio of all considered predictions to the POWHEG+PYTHIA prediction. The top quark status is required to be after parton shower radiation. The samples are generated for pp collisions at 7 TeV centre of mass energy. The corresponding distributions from ATLAS show consistent result with CMS.
treeATLASCMScomparisonCMSonlyFineBinningtopPtHERWIG.png The distribution of the transverse momentum, pT, of the top quark in ttbar events at the generator (parton) level is shown for CMS samples produced with generators coupled to HERWIG for parton shower and hadronization. The lower part of the figure shows the ratio of all considered predictions to the POWHEG+HERWIG prediction. The top quark status is required to be after parton shower radiation. The samples are generated for pp collisions at 7 TeV centre of mass energy. The corresponding distributions from ATLAS show consistent result with CMS.
treeATLASCMScomparisonCMSonlyFineBinningtopPtPYTHIA.png The distribution of the transverse momentum, pT, of the top quark in ttbar events at the generator (parton) level is shown for CMS samples produced with generators coupled to PYTHIA for parton shower and hadronization. The lower part of the figure shows the ratio of all considered predictions to the POWHEG+PYTHIA prediction. The top quark status is required to be after parton shower radiation. The samples are generated for pp collisions at 7 TeV centre of mass energy. The corresponding distributions from ATLAS show consistent result with CMS.
treeATLASCMScomparisonCMSonlyFineBinningtopPtPowheg.png The distribution of the transverse momentum, pT, of the top quark in ttbar events at the generator (parton) level is shown for CMS samples produced with the POWHEG generator coupled to both PYTHIA and HERWIG for parton shower and hadronization. The lower part of the figure shows the ratio of all considered predictions to the POWHEG+HERWIG prediction. The top quark status is required to be after parton shower radiation. The samples are generated for pp collisions at 7 TeV centre of mass energy. The corresponding distributions from ATLAS show consistent result with CMS.

treeATLASCMScomparisonCMSonlyFineBinningttbarPt.png The distribution of the transverse momentum, pT, of the ttbar system in ttbar events at the generator (parton) level is shown for all CMS samples used in the ttbar differential cross section analyses. The lower part of the figure shows the ratio of all considered predictions to the POWHEG+PYTHIA prediction. The top quark status is required to be after parton shower radiation. The samples are generated for pp collisions at 7 TeV centre of mass energy. The corresponding distributions from ATLAS show consistent result with CMS.
treeATLASCMScomparisonCMSonlyFineBinningttbarPtHERWIG.png The distribution of the transverse momentum, pT, of the ttbar system in ttbar events at the generator (parton) level is shown for CMS samples produced with generators coupled to HERWIG for parton shower and hadronization. The lower part of the figure shows the ratio of all considered predictions to the POWHEG+HERWIG prediction. The top quark status is required to be after parton shower radiation. The samples are generated for pp collisions at 7 TeV centre of mass energy. The corresponding distributions from ATLAS show consistent result with CMS.
treeATLASCMScomparisonCMSonlyFineBinningttbarPtPYTHIA.png The distribution of the transverse momentum, pT, of the ttbar system in ttbar events at the generator (parton) level is shown for CMS samples produced with generators coupled to PYTHIA for parton shower and hadronization. The lower part of the figure shows the ratio of all considered predictions to the POWHEG+PYTHIA prediction. The top quark status is required to be after parton shower radiation. The samples are generated for pp collisions at 7 TeV centre of mass energy. The corresponding distributions from ATLAS show consistent result with CMS.
treeATLASCMScomparisonCMSonlyFineBinningttbarPtPowheg.png The distribution of the transverse momentum, pT, of the ttbar system in ttbar events at the generator (parton) level is shown for CMS samples produced with the POWHEG generator coupled to both PYTHIA and HERWIG for parton shower and hadronization. The lower part of the figure shows the ratio of all considered predictions to the POWHEG+HERWIG prediction. The top quark status is required to be after parton shower radiation. The samples are generated for pp collisions at 7 TeV centre of mass energy. The corresponding distributions from ATLAS show consistent result with CMS.

treeATLASCMScomparisonCMSonlyFineBinningttbarY.png The distribution of the rapidity, y, of the ttbar system in ttbar events at the generator (parton) level is shown for all CMS samples used in the ttbar differential cross section analyses. The lower part of the figure shows the ratio of all considered predictions to the POWHEG+PYTHIA prediction. The top quark status is required to be after parton shower radiation. The samples are generated for pp collisions at 7 TeV centre of mass energy. The corresponding distributions from ATLAS show consistent result with CMS.
treeATLASCMScomparisonCMSonlyFineBinningttbarYHERWIG.png The distribution of the rapidity, y, of the ttbar system in ttbar events at the generator (parton) level is shown for CMS samples produced with generators coupled to HERWIG for parton shower and hadronization. The lower part of the figure shows the ratio of all considered predictions to the POWHEG+HERWIG prediction. The top quark status is required to be after parton shower radiation. The samples are generated for pp collisions at 7 TeV centre of mass energy. The corresponding distributions from ATLAS show consistent result with CMS.
treeATLASCMScomparisonCMSonlyFineBinningttbarYPYTHIA.png The distribution of the rapidity, y, of the ttbar system in ttbar events at the generator (parton) level is shown for CMS samples produced with generators coupled to PYTHIA for parton shower and hadronization. The lower part of the figure shows the ratio of all considered predictions to the POWHEG+PYTHIA prediction. The top quark status is required to be after parton shower radiation. The samples are generated for pp collisions at 7 TeV centre of mass energy. The corresponding distributions from ATLAS show consistent result with CMS.
treeATLASCMScomparisonCMSonlyFineBinningttbarYPowheg.png The distribution of the rapidity, y, of the ttbar system in ttbar events at the generator (parton) level is shown for CMS samples produced with the POWHEG generator coupled to both PYTHIA and HERWIG for parton shower and hadronization. The lower part of the figure shows the ratio of all considered predictions to the POWHEG+HERWIG prediction. The top quark status is required to be after parton shower radiation. The samples are generated for pp collisions at 7 TeV centre of mass energy. The corresponding distributions from ATLAS show consistent result with CMS.

-- MariaAldaya - 30 Jan 2014

Topic attachments
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PNGpng fit_mtop_13TeV.png r1 manage 137.1 K 2014-03-04 - 17:44 MariaAldaya  
PNGpng fit_mtop_14TeV.png r1 manage 135.3 K 2014-03-04 - 17:44 MariaAldaya  
JPEGjpeg fit_mtop_7TeV.jpeg r1 manage 787.3 K 2014-01-30 - 20:54 MariaAldaya  
JPEGjpg fit_mtop_8TeV.jpg r1 manage 632.7 K 2014-03-04 - 17:44 MariaAldaya  
JPEGjpeg fit_sqrts_mtop1725.jpeg r1 manage 762.4 K 2014-01-30 - 20:54 MariaAldaya  
JPEGjpeg fit_sqrts_mtop1732.jpeg r1 manage 761.4 K 2014-01-30 - 20:54 MariaAldaya  
PNGpng lhctopwg_timeline_paper.png r1 manage 225.1 K 2021-04-08 - 14:21 MariaAldaya  
PNGpng lhctopwg_timeline_plots.png r1 manage 225.3 K 2021-04-08 - 14:16 MariaAldaya  
PNGpng lhctopwg_timeline_preliminaries.png r1 manage 288.1 K 2021-04-08 - 14:16 MariaAldaya  
Texttxt massdep-param.py.txt r1 manage 0.4 K 2014-01-31 - 17:09 JamesFerrando Python examples of parametrisations
Texttxt rootsdep-param.py.txt r1 manage 0.4 K 2014-01-31 - 17:09 JamesFerrando Python examples of parametrisations
PNGpng sigma_vs_mass_formula.png r1 manage 14.2 K 2014-01-30 - 20:54 MariaAldaya  
PNGpng sigma_vs_sqrts_formula.png r1 manage 14.1 K 2014-01-30 - 20:54 MariaAldaya  
PNGpng treeATLASCMScomparisonCMSonlyFineBinningtopPt.png r1 manage 19.2 K 2014-12-10 - 19:40 MariaAldaya  
PNGpng treeATLASCMScomparisonCMSonlyFineBinningtopPtHERWIG.png r1 manage 16.8 K 2014-12-10 - 19:40 MariaAldaya  
PNGpng treeATLASCMScomparisonCMSonlyFineBinningtopPtPYTHIA.png r1 manage 16.4 K 2014-12-10 - 19:40 MariaAldaya  
PNGpng treeATLASCMScomparisonCMSonlyFineBinningtopPtPowheg.png r1 manage 17.0 K 2014-12-10 - 19:40 MariaAldaya  
PNGpng treeATLASCMScomparisonCMSonlyFineBinningttbarPt.png r1 manage 18.1 K 2014-12-10 - 19:40 MariaAldaya  
PNGpng treeATLASCMScomparisonCMSonlyFineBinningttbarPtHERWIG.png r1 manage 16.1 K 2014-12-10 - 19:40 MariaAldaya  
PNGpng treeATLASCMScomparisonCMSonlyFineBinningttbarPtPYTHIA.png r1 manage 15.9 K 2014-12-10 - 19:40 MariaAldaya  
PNGpng treeATLASCMScomparisonCMSonlyFineBinningttbarPtPowheg.png r1 manage 16.2 K 2014-12-10 - 19:40 MariaAldaya  
PNGpng treeATLASCMScomparisonCMSonlyFineBinningttbarY.png r1 manage 19.8 K 2015-04-02 - 18:36 MariaAldaya  
PNGpng treeATLASCMScomparisonCMSonlyFineBinningttbarYHERWIG.png r1 manage 17.1 K 2014-12-10 - 19:40 MariaAldaya  
PNGpng treeATLASCMScomparisonCMSonlyFineBinningttbarYPYTHIA.png r1 manage 16.9 K 2014-12-10 - 19:40 MariaAldaya  
PNGpng treeATLASCMScomparisonCMSonlyFineBinningttbarYPowheg.png r1 manage 16.9 K 2015-04-02 - 18:36 MariaAldaya  
PDFpdf tt_xsec_lhc.pdf r1 manage 42.3 K 2014-02-03 - 16:40 MariaAldaya  
PNGpng tt_xsec_lhc.png r1 manage 53.4 K 2014-02-03 - 16:40 MariaAldaya  
PNGpng tt_xsec_vsroots.png r1 manage 28.5 K 2014-03-04 - 17:57 MariaAldaya  
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