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CMS-PAS-TOP-15-006
Measurement of the differential production cross section for top-quark pairs as a function of jet multiplicity in the lepton+jets final state at $\sqrt{s}= $ 8 TeV with the CMS detector
Abstract: The top-quark pair differential production cross section in pp collisions at $ \sqrt{s} = $ 8 TeV as a function of the number of jets is measured in the lepton+jets ($\mathrm{e}$/$\mu$+jets) final state for an integrated luminosity of 19.7 fb$^{-1}$. The cross section is presented in the visible phase space of the measurement as well as extrapolated to the full phase space. The results are compared with theoretical predictions at next-to-leading order. The comparisons show good agreement between the data and the predictions within the experimental and theoretical uncertainties.
Figures & Tables Summary References CMS Publications
Figures

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Figure 1-a:
Distribution of the number of selected jets (a), the missing transverse energy (b), the ${p_{\mathrm {T}}}$ and $\eta $ of all selected jets (c,d), and the ${p_{\mathrm {T}}}$ and $\eta $ of the leading jet (e,f), combining the $\mathrm{e}$+jets and $\mu $+jets channels. The lower part of each plot shows the ratio of the data to the MC predictions. The hashed areas represent the shape uncertainties affecting the MC signal and backgrounds. The normalization of the signal and background processes is discussed in the text.

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Figure 1-b:
Distribution of the number of selected jets (a), the missing transverse energy (b), the ${p_{\mathrm {T}}}$ and $\eta $ of all selected jets (c,d), and the ${p_{\mathrm {T}}}$ and $\eta $ of the leading jet (e,f), combining the $\mathrm{e}$+jets and $\mu $+jets channels. The lower part of each plot shows the ratio of the data to the MC predictions. The hashed areas represent the shape uncertainties affecting the MC signal and backgrounds. The normalization of the signal and background processes is discussed in the text.

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Figure 1-c:
Distribution of the number of selected jets (a), the missing transverse energy (b), the ${p_{\mathrm {T}}}$ and $\eta $ of all selected jets (c,d), and the ${p_{\mathrm {T}}}$ and $\eta $ of the leading jet (e,f), combining the $\mathrm{e}$+jets and $\mu $+jets channels. The lower part of each plot shows the ratio of the data to the MC predictions. The hashed areas represent the shape uncertainties affecting the MC signal and backgrounds. The normalization of the signal and background processes is discussed in the text.

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Figure 1-d:
Distribution of the number of selected jets (a), the missing transverse energy (b), the ${p_{\mathrm {T}}}$ and $\eta $ of all selected jets (c,d), and the ${p_{\mathrm {T}}}$ and $\eta $ of the leading jet (e,f), combining the $\mathrm{e}$+jets and $\mu $+jets channels. The lower part of each plot shows the ratio of the data to the MC predictions. The hashed areas represent the shape uncertainties affecting the MC signal and backgrounds. The normalization of the signal and background processes is discussed in the text.

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Figure 1-e:
Distribution of the number of selected jets (a), the missing transverse energy (b), the ${p_{\mathrm {T}}}$ and $\eta $ of all selected jets (c,d), and the ${p_{\mathrm {T}}}$ and $\eta $ of the leading jet (e,f), combining the $\mathrm{e}$+jets and $\mu $+jets channels. The lower part of each plot shows the ratio of the data to the MC predictions. The hashed areas represent the shape uncertainties affecting the MC signal and backgrounds. The normalization of the signal and background processes is discussed in the text.

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Figure 1-f:
Distribution of the number of selected jets (a), the missing transverse energy (b), the ${p_{\mathrm {T}}}$ and $\eta $ of all selected jets (c,d), and the ${p_{\mathrm {T}}}$ and $\eta $ of the leading jet (e,f), combining the $\mathrm{e}$+jets and $\mu $+jets channels. The lower part of each plot shows the ratio of the data to the MC predictions. The hashed areas represent the shape uncertainties affecting the MC signal and backgrounds. The normalization of the signal and background processes is discussed in the text.

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Figure 2-a:
Combined differential visible $ {\mathrm{ t \bar{t} } } $ cross section as a function of the number of particle-level jets in the $\ell $+jets channel. The results are compared to predictions from various generators (a) or from MadGraph with various parameter sets (b). The vertical bars represent the total uncertainties and the intersecting horizontal bars represent the statistical uncertainties alone. In the ratio plot for mc@nlo and MadGraph with varied $Q^2$ value, the band represents the uncertainty of the measurement.

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Figure 2-b:
Combined differential visible $ {\mathrm{ t \bar{t} } } $ cross section as a function of the number of particle-level jets in the $\ell $+jets channel. The results are compared to predictions from various generators (a) or from MadGraph with various parameter sets (b). The vertical bars represent the total uncertainties and the intersecting horizontal bars represent the statistical uncertainties alone. In the ratio plot for mc@nlo and MadGraph with varied $Q^2$ value, the band represents the uncertainty of the measurement.

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Figure 3-a:
Combined differential visible $ {\mathrm{ t \bar{t} } } $ cross section as a function of the number of particle-level jets in the $\ell $+jets channel. The results are compared to predictions from various MC generators (a) and SHERPA $Q^{2}$ (b). The vertical bars represent the total uncertainties and the intersecting vertical bars represent the statistical uncertainties alone. In the ratio plot, the band represents the uncertainty of the measurement.

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Figure 3-b:
Combined differential visible $ {\mathrm{ t \bar{t} } } $ cross section as a function of the number of particle-level jets in the $\ell $+jets channel. The results are compared to predictions from various MC generators (a) and SHERPA $Q^{2}$ (b). The vertical bars represent the total uncertainties and the intersecting vertical bars represent the statistical uncertainties alone. In the ratio plot, the band represents the uncertainty of the measurement.
Tables

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Table 1:
Production cross section of $ {\mathrm{ t \bar{t} } } $ pairs versus the particle-level jet multiplicity in the $\ell $+jets channel. The relative statistical, experimental, theoretical and total uncertainties are also shown. Total uncertainties include the luminosity uncertainty of 2.6%.

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Table 2:
Normalized production cross section of $ {\mathrm{ t \bar{t} } } $ pairs versus the particle-level jet multiplicity in the $\ell $+jets channel. The relative statistical, experimental, theoretical and total uncertainties are also shown.

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Table 3:
Comparison between the measured differential production cross section and predictions from various generators. A $\chi ^{2}$ and a $p$-value are calculated using the covariance matrix of the measured cross sections. The number of degrees of freedom (NDF) are equal to the number of the jet multiplicity bins.

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Table 4:
Associated production cross section of $ {\mathrm{ t \bar{t} } } $ pairs with 0-4 jets in the final state, from the combination of the $\mathrm{e}$+jets and $\mu $+jets channels, extrapolated to the full phase space. The relative statistical, experimental, theoretical and total uncertainties are also shown. Total uncertainties include the luminosity uncertainty of 2.6%.
Summary
The differential production cross section of a top-quark pair as a function of the number of jets is presented in the lepton+jet final state for an integrated luminosity of 19.7 fb$^{-1}$ at $\sqrt{s}= $ 8 TeV pp collisions. The cross section is presented in the visible phase space of the measurement for exactly 4-9 and 10 or more particle-level jets in the final state as well as to the extrapolated full phase space for equal or more than 0-4 additional jets. The results are compared with the theoretical predictions as well as other published experimental results. The comparisons show consistency with the predictions within the experimental and theoretical uncertainties. The measurement in the visible phase space have been performed in a way to be fully compatible with predictions at particle level for model testing purposes.
References
1 S. Dittmaier, P. Uwer, and S. Weinzierl NLO QCD corrections to t anti-t + jet production at hadron colliders PRL 98 (2007) 262002 hep-ph/0703120
2 G. Bevilacqua, M. Czakon, C. Papadopoulos, and M. Worek Hadronic top-quark pair production in association with two jets at Next-to-Leading Order QCD PRD 84 (2011) 11401 1108.2851
3 CMS Collaboration Search for the standard model Higgs boson produced in association with a top-quark pair in pp collisions at the LHC JHEP 05 (2013) 145 CMS-HIG-12-035
1303.0763
4 ATLAS Collaboration Measurement of the $ t\overline{t} $ production cross-section as a function of jet multiplicity and jet transverse momentum in 7 TeV proton-proton collisions with the ATLAS detector JHEP 01 (2015) 020 1407.0891
5 ATLAS Collaboration Measurements of fiducial cross-sections for $ t\bar{t} $ production with one or two additional b-jets in pp collisions at $ \sqrt{s} $ =8 TeV using the ATLAS detector EPJC76 (2016), no. 1, 11 1508.06868
6 CMS Collaboration Measurement of the $ t \bar{t} $ production cross section in the dilepton channel in pp collisions at $ \sqrt{s} $ = 8 TeV JHEP 02 (2014) 024, , [Erratum: JHEP02,102(2014)] CMS-TOP-12-007
1312.7582
7 CMS Collaboration Measurement of the differential cross section for top quark pair production in pp collisions at $ \sqrt{s} = 8\,\text {TeV} $ EPJC75 (2015), no. 11, 542 CMS-TOP-12-028
1505.04480
8 CMS Collaboration Measurement of the cross section ratio $ \sigma_\mathrm{t \bar{t} b \bar{b}} / \sigma_\mathrm{t \bar{t} jj } $ in pp collisions at $ \sqrt{s} $ = 8 TeV PLB746 (2015) 132--153 CMS-TOP-13-010
1411.5621
9 CMS Collaboration Measurement of jet multiplicity distributions in $ \mathrm {t}\overline{\mathrm {t}} $ production in pp collisions at $ \sqrt{s} = 7\,\text {TeV} $ EPJC74 (2015) 3014, , [Erratum: Eur. Phys. J.C75,no.5,216(2015)] CMS-TOP-12-018
1404.3171
10 J. Alwall et al. $ \MADGRAPH $ 5 : Going Beyond JHEP 06 (2011) 128 1106.0522
11 P. Nason A New method for combining NLO QCD with shower Monte Carlo algorithms JHEP 0411 (2004) 040 hep-ph/0409146
12 S. Frixione, P. Nason, and C. Oleari Matching NLO QCD computations with Parton Shower simulations: the POWHEG method JHEP 11 (2007) 070 0709.2092
13 S. Alioli, P. Nason, C. Oleari, and M. Re A general framework for implementing NLO calculations in shower Monte Carlo programs: the POWHEG BOX JHEP 1006 (2010) 043 1002.2581
14 T. Sjostrand, S. Mrenna, and P. Z. Skands PYTHIA 6.4 physics and manual JHEP 05 (2006) 026 hep-ph/0603175
15 J. Pumplin et al. New generation of parton distributions with uncertainties from global QCD analysis JHEP 07 (2002) 012 hep-ph/0201195
16 H.-L. Lai et al. New parton distributions for collider physics PRD82 (2010) 074024 1007.2241
17 R. Field Min-bias and the underlying event at the LHC Acta Physics Polonica B 42 (2011) 2631
18 GEANT4 Collaboration GEANT 4 -- a simulation toolkit NIMA 506 (2003) 250
19 M. Czakon and A. Mitov Top++: A Program for the Calculation of the Top-Pair Cross-Section at Hadron Colliders CPC 185 (2014) 2930 1112.5675
20 N. Kidonakis Differential and total cross sections for top pair and single top production 1205.3453
21 K. Melnikov and F. Petriello Electroweak gauge boson production at hadron colliders through O(alpha(s)**2) Phys.Rev. D74 (2006) 114017 hep-ph/0609070
22 J. M. Campbell and R. K. Ellis Radiative corrections to Z b anti-b production Phys.Rev. D62 (2000) 114012 hep-ph/0006304
23 J. M. Campbell and R. K. Ellis $ t \bar{t} W^{+-} $ production and decay at NLO JHEP 07 (2012) 052 1204.5678
24 M. V. Garzelli, A. Kardos, C. G. Papadopoulos, and Z. Trocsanyi $ \mathrm{t} \mathrm{ \bar{t} } \mathrm{ W }^{+-} $ and $ \mathrm{t} \mathrm{ \bar{t} } \mathrm{ Z } $ Hadroproduction at NLO accuracy in QCD with Parton Shower and Hadronization effects JHEP 11 (2012) 056 1208.2665
25 G. Antchev et al. First measurement of the total proton-proton cross section at the LHC energy of $ \sqrt{s} $ =7 TeV Europhys. Lett. 96 (2011) 21002 1110.1395
26 CMS Collaboration Commissioning of the Particle-Flow reconstruction in Minimum-Bias and Jet Events from pp Collisions at 7 TeV CDS
27 CMS Collaboration Performance of electron reconstruction and selection with the CMS detector in proton-proton collisions at $ \sqrt{s} = $ 8 TeV JINST 10 (2015), no. 06, P06005 CMS-EGM-13-001
1502.02701
28 A. Hoecker et al. TMVA - Toolkit for Multivariate Data Analysis PoS ACAT 040 (2007) 0703039
29 CMS Collaboration Performance of CMS muon reconstruction in pp collision events at $ \sqrt{s} = $ 7 TeV JINST 7 (2012) P10002 CMS-MUO-10-004
1206.4071
30 CMS Collaboration Description and performance of track and primary-vertex reconstruction with the CMS tracker JINST 9 (2014), no. 10, P10009 CMS-TRK-11-001
1405.6569
31 M. Cacciari, G. Salam, and G. Soyez The anti-kt jet clustering algortihm JHEP 04 (2008) 063 0802.1189
32 CMS Collaboration Determination of Jet Energy Calibration and Transverse Momentum Resolution in CMS JINST 6 (2011) P11002 CMS-JME-10-011
1107.4277
33 CMS Collaboration Identification of b-quark jets with the CMS experiment JINST 8 (2013) P04013 CMS-BTV-12-001
1211.4462
34 CMS Collaboration Measurement of the $ t\bar{t} $ production cross section in $ pp $ collisions at $ \sqrt{s}=7 $ TeV with lepton + jets final states Physics Letters B 720 (2013), no. 120133, 83 -- 104
35 V. Blobel An Unfolding method for high-energy physics experiments in Advanced statistical techniques in particle physics. Proceedings, Conference, Durham, UK, March 18-22, 2002, pp. 258--267 2002 hep-ex/0208022
36 CMS Collaboration Inclusive and differential measurements of the $ \mathrm{ t \bar{t} } $ charge asymmetry in pp collisions at $ \sqrt{s} = $ 8 TeV CMS-TOP-12-033
1507.03119
37 A. Hocker and V. Kartvelishvili SVD approach to data unfolding NIMA372 (1996) 469--481 hep-ph/9509307
38 F. James Statistical Methods in Experimental Physics World Scientific, Singapore, 2 edition
39 M. Cacciari, G. P. Salam, and G. Soyez The Catchment Area of Jets JHEP 04 (2008) 005 0802.1188
40 G. Bevilacqua and M. Worek On the ratio of $ t\overline{t} b\overline{b} $ and $ t\overline{t} jj $ cross sections at the CERN Large Hadron Collider JHEP 07 (2014) 135 1403.2046
41 CMS Collaboration Jet Energy Resolution in CMS at $ \sqrt{s} = $ 7 TeV CDS
42 CMS Collaboration CMS Luminosity Based on Pixel Cluster Counting - Summer 2013 Update CMS-PAS-LUM-13-001 CMS-PAS-LUM-13-001
43 D. Bourilkov, R. C. Group, and M. R. Whalley LHAPDF: PDF use from the Tevatron to the LHC in TeV4LHC Workshop - 4th meeting Batavia, Illinois, October 20-22, 2005 2006 hep-ph/0605240
44 Z. Sullivan and P. M. Nadolsky Heavy quark parton distribution functions and their uncertainties eConf C010630 (2001) P511 hep-ph/0111358
45 P. M. Nadolsky and Z. Sullivan PDF uncertainties in WH production at Tevatron eConf C010630 (2001) P510 hep-ph/0110378
46 N. Kidonakis NNLL threshold resummation for top-pair and single-top production Phys. Part. Nucl. 45 (2014), no. 4, 714--722 1210.7813
47 L. Lyons, D. Gibaut, and P. Clifford How to Combine Correlated Estimates of a Single Physical Quantity NIMA270 (1988) 110
48 A. Valassi Combining correlated measurements of several different physical quantities NIMA500 (2003) 391--405
49 A. Valassi and R. Chierici Information and treatment of unknown correlations in the combination of measurements using the BLUE method EPJC74 (2014) 2717 1307.4003
50 G. Corcella et al. HERWIG 6.5: An event generator for hadron emission reaction with interfering gluons JHEP 01 (2001) 010 0011363
51 S. Frixione and B. Webber Matching NLO QCD computations and parton shower simulations JHEP 0206 (2002) 029 0204244
52 A. Buckley et al. Rivet user manual CPC 184 (2013) 2803--2819 1003.0694
53 M. Dobbs and J. B. Hansen The HepMC C++ Monte Carlo event record for High Energy Physics CPC 134 (2001) 41--46
54 J. Alwall et al. The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations JHEP 1407 (2014) 079 1405.0301
55 T. Gleisberg et al. Event generation with SHERPA 1.1 JHEP 0902 (2009) 007 0811.4622
56 T. Sjostrand, S. Mrenna, and P. Z. Skands A Brief Introduction to PYTHIA 8.1 CPC 178 (2008) 852--867 0710.3820
57 M. Botje et al. The PDF4LHC Working Group Interim Recommendations 1101.0538
58 A. D. Martin, W. J. Stirling, R. S. Thorne, and G. Watt Uncertainties on $ \alpha_{s} $ in global PDF analyses and implications for predicted hadronic cross sections EPJC64 (2009) 653--680 0905.3531
59 J. Gao et al. CT10 next-to-next-to-leading order global analysis of QCD PRD89 (2014), no. 3, 033009 1302.6246
60 R. D. Ball et al. Parton distributions with LHC data Nuclear Physics B 867 (2013), no. 2, 244 -- 289
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