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CMS-PAS-TOP-17-018
Measurement of the production cross section for single top quarks in association with W bosons in pp collisions at $\sqrt{s}= $ 13 TeV
Abstract: A measurement of the associated production of a single top quark and a W boson in pp collisions at $\sqrt{s}= $ 13 TeV with the CMS experiment at the CERN LHC is presented. The data set, collected in 2016, corresponds to an integrated luminosity of 35.9 fb$^{-1}$. The measurement is performed in the dilepton final state, using events with one electron and one muon. A multivariate discriminant, exploiting kinematic properties of events, is used to separate the signal from the dominant ${\rm t\bar{t}}$ background. The measured cross section of $\sigma = $ 63.1 $\pm$ 1.8 (stat) $\pm$ 6.0 ( (syst) $\pm$ 2.1 (lumi) pb is in agreement with the standard model expectation.
Figures & Tables Summary References CMS Publications
Figures

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Figure 1:
Leading order Feynman diagrams for single top quark production in the tW mode, the charge-conjugate modes are implicitly included.

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Figure 1-a:
Leading order Feynman diagrams for single top quark production in the tW mode, the charge-conjugate modes are implicitly included.

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Figure 1-b:
Leading order Feynman diagrams for single top quark production in the tW mode, the charge-conjugate modes are implicitly included.

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Figure 2:
Comparison of several lepton kinematic variables for the observed data and simulated events after the dilepton selection is applied. The error band includes the statistical and all systematic uncertainties but the ones from background normalization and luminosity. The bottom of each panel shows the ratios of data to the sum of the expected yields.

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Figure 2-a:
Comparison of several lepton kinematic variables for the observed data and simulated events after the dilepton selection is applied. The error band includes the statistical and all systematic uncertainties but the ones from background normalization and luminosity. The bottom of each panel shows the ratios of data to the sum of the expected yields.

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Figure 2-b:
Comparison of several lepton kinematic variables for the observed data and simulated events after the dilepton selection is applied. The error band includes the statistical and all systematic uncertainties but the ones from background normalization and luminosity. The bottom of each panel shows the ratios of data to the sum of the expected yields.

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Figure 2-c:
Comparison of several lepton kinematic variables for the observed data and simulated events after the dilepton selection is applied. The error band includes the statistical and all systematic uncertainties but the ones from background normalization and luminosity. The bottom of each panel shows the ratios of data to the sum of the expected yields.

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Figure 2-d:
Comparison of several lepton kinematic variables for the observed data and simulated events after the dilepton selection is applied. The error band includes the statistical and all systematic uncertainties but the ones from background normalization and luminosity. The bottom of each panel shows the ratios of data to the sum of the expected yields.

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Figure 2-e:
Comparison of several lepton kinematic variables for the observed data and simulated events after the dilepton selection is applied. The error band includes the statistical and all systematic uncertainties but the ones from background normalization and luminosity. The bottom of each panel shows the ratios of data to the sum of the expected yields.

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Figure 2-f:
Comparison of several lepton kinematic variables for the observed data and simulated events after the dilepton selection is applied. The error band includes the statistical and all systematic uncertainties but the ones from background normalization and luminosity. The bottom of each panel shows the ratios of data to the sum of the expected yields.

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Figure 3:
Yields observed in data compared with those expected from simulation as a function of the number of jets and number of b-tagged jets for events passing the baseline dileptonic selection. The error band includes the statistical and all systematic uncertainties but the ones from background normalization and luminosity. The bottom of each panel shows the ratios of data to the sum of the expected yields.

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Figure 4:
Most discriminat variables used for the training of the BDT in the 1j1b category. The error band includes the statistical and all systematic uncertainties but the ones from background normalization and luminosity. The bottom of each panel shows the ratios of data to the sum of the expected yields.

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Figure 4-a:
Most discriminat variables used for the training of the BDT in the 1j1b category. The error band includes the statistical and all systematic uncertainties but the ones from background normalization and luminosity. The bottom of each panel shows the ratios of data to the sum of the expected yields.

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Figure 4-b:
Most discriminat variables used for the training of the BDT in the 1j1b category. The error band includes the statistical and all systematic uncertainties but the ones from background normalization and luminosity. The bottom of each panel shows the ratios of data to the sum of the expected yields.

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Figure 4-c:
Most discriminat variables used for the training of the BDT in the 1j1b category. The error band includes the statistical and all systematic uncertainties but the ones from background normalization and luminosity. The bottom of each panel shows the ratios of data to the sum of the expected yields.

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Figure 4-d:
Most discriminat variables used for the training of the BDT in the 1j1b category. The error band includes the statistical and all systematic uncertainties but the ones from background normalization and luminosity. The bottom of each panel shows the ratios of data to the sum of the expected yields.

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Figure 5:
Comparison of the BDT output in the 1j1b (left) and 2j1b (center) regions and the $ {p_{\mathrm {T}}} $ of the subleading jet in the 2j2b region (right) distributions after the fit is performed for the observed data and simulated events. The error band includes the statistical and systematic uncertainties. The bottom of each panel shows the ratios of data to the sum of the expected yields.

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Figure 5-a:
Comparison of the BDT output in the 1j1b (left) and 2j1b (center) regions and the $ {p_{\mathrm {T}}} $ of the subleading jet in the 2j2b region (right) distributions after the fit is performed for the observed data and simulated events. The error band includes the statistical and systematic uncertainties. The bottom of each panel shows the ratios of data to the sum of the expected yields.

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Figure 5-b:
Comparison of the BDT output in the 1j1b (left) and 2j1b (center) regions and the $ {p_{\mathrm {T}}} $ of the subleading jet in the 2j2b region (right) distributions after the fit is performed for the observed data and simulated events. The error band includes the statistical and systematic uncertainties. The bottom of each panel shows the ratios of data to the sum of the expected yields.

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Figure 5-c:
Comparison of the BDT output in the 1j1b (left) and 2j1b (center) regions and the $ {p_{\mathrm {T}}} $ of the subleading jet in the 2j2b region (right) distributions after the fit is performed for the observed data and simulated events. The error band includes the statistical and systematic uncertainties. The bottom of each panel shows the ratios of data to the sum of the expected yields.
Tables

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Table 1:
Estimation of the effect of each source of systematic uncertainty to the fit.
Summary
The full data set recorded by CMS at 13 TeV during 2016, corresponding to an integrated luminosity of 35.9 fb$^{-1}$, is used to measure the tW production cross section in the $\mathrm{e^{\pm}}\mu^{\mp}$ channel. The signal is measured using a maximum likelihood fit to the distribution of BDT discriminants in the 1j1b and 2j1b categories and the subleading jet $ {p_{\mathrm{T}}} $ distribution in the 2j2b category. The measured cross section of the tW production is found to be $\sigma = $ 63.1 $\pm$ 1.8 (stat) $\pm$ 6.0 ( (syst) $\pm$ 2.1 (lumi) pb. A relative uncertainty of 10% in the tW production cross section is achieved. This is the first measurement of this process by the CMS experiment at $ \sqrt{s} = $ 13 TeV. The measured cross section is consistent with the standard model prediction of 71.7 $\pm$ 1.8 (scale) $\pm$ 3.4 (PDF) pb and with a similar measurement by the ATLAS collaboration [13].
References
1 CDF Collaboration First Observation of Electroweak Single Top Quark Production PRL 103 (2009) 092002 0903.0885
2 D0 Collaboration Observation of Single Top Quark Production PRL 103 (2009) 092001 0903.0850
3 S. Frixione et al. Single-top hadroproduction in association with a W boson JHEP 07 (2008) 029 0805.3067
4 A. S. Belyaev, E. E. Boos, and L. V. Dudko Single top quark at future hadron colliders: Complete signal and background study PRD 59 (1999) 075001 hep-ph/9806332
5 C. D. White, S. Frixione, E. Laenen, and F. Maltoni Isolating Wt production at the LHC JHEP 11 (2009) 074 0908.0631
6 T. M. P. Tait and C. P. Yuan Single top quark production as a window to physics beyond the standard model PRD 63 (2000) 014018 hep-ph/0007298
7 Q.-H. Cao, J. Wudka, and C. P. Yuan Search for new physics via single top production at the LHC PLB 658 (2007) 50--56 0704.2809
8 V. Barger, M. McCaskey, and G. Shaughnessy Single top and Higgs associated production at the LHC PRD 81 (2010) 034020 0911.1556
9 CMS Collaboration Evidence for associated production of a single top quark and W boson in $ pp $ collisions at $ \sqrt{s} = $ 7 TeV PRL 110 (2013) 022003 CMS-TOP-11-022
1209.3489
10 ATLAS Collaboration Evidence for the associated production of a $ W $ boson and a top quark in ATLAS at $ \sqrt{s}= $ 7 TeV PLB 716 (2012) 142--159 1205.5764
11 CMS Collaboration Observation of the associated production of a single top quark and a $ W $ boson in $ pp $ collisions at $ \sqrt s = $ 8 TeV PRL 112 (2014), no. 23, 231802 CMS-TOP-12-040
1401.2942
12 ATLAS Collaboration Measurement of the production cross-section of a single top quark in association with a $ W $ boson at 8 TeV with the ATLAS experiment JHEP 01 (2016) 064 1510.03752
13 ATLAS Collaboration Measurement of the cross-section for producing a $ W $ boson in association with a single top quark in $ pp $ collisions at $ \sqrt{s}={13} $ TeV with ATLAS 1612.07231
14 N. Kidonakis Theoretical results for electroweak-boson and single-top production PoS DIS2015 (2015) 170 1506.04072
15 E. Re Single-top Wt-channel production matched with parton showers using the POWHEG method EPJC 71 (2011) 1547 1009.2450
16 NNPDF Collaboration Parton distributions for the LHC Run II JHEP 04 (2015) 040 1410.8849
17 T. Sjostrand, S. Mrenna, and P. Skands PYTHIA 6.4 physics and manual JHEP 05 (2006) 026 hep-ph/0603175
18 T. Sjostrand et al. An Introduction to PYTHIA 8.2 CPC 191 (2015) 159 1410.3012
19 CMS Collaboration Underlying Event Tunes and Double Parton Scattering CMS-PAS-GEN-14-001
20 P. Skands, S. Carrazza, and J. Rojo Tuning PYTHIA 8.1: the Monash 2013 Tune EPJC 74 (2014), no. 8 1404.5630
21 T. M. P. Tait $ t{W}^{{-}} $ mode of single top quark production PRD 61 (1999) 034001
22 S. Alioli et al. A general framework for implementing NLO calculations in shower Monte Carlo programs: the POWHEG BOX JHEP 06 (2010) 043 1002.2581
23 CMS Collaboration Investigations of the impact of the parton shower tuning in Pythia 8 in the modelling of $ \mathrm{t\overline{t}} $ at $ \sqrt{s}= $ 8 and 13 TeV CMS-PAS-TOP-16-021 CMS-PAS-TOP-16-021
24 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 07 (2014) 079 1405.0301
25 R. Frederix and S. Frixione Merging meets matching in MC@NLO JHEP 12 (2012) 061 1209.6215
26 Y. Li and F. Petriello Combining qcd and electroweak corrections to dilepton production in the framework of the fewz simulation code PRD 86 (2012) 094034
27 J. M. Campbell, R. K. Ellis, and C. Williams Vector boson pair production at the LHC JHEP 07 (2011) 018 1105.0020
28 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
29 S. Alekhin et al. The PDF4LHC Working Group Interim Report 1101.0536
30 M. Botje et al. The PDF4LHC Working Group Interim Recommendations 1101.0538
31 H.-L. Lai et al. New parton distributions for collider physics PRD 82 (2010) 074024 1007.2241
32 J. Gao et al. CT10 next-to-next-to-leading order global analysis of QCD PRD 89 (2014) 033009 1302.6246
33 NNPDF Collaboration Parton distributions with LHC data NPB 867 (2013) 244 1207.1303
34 CMS Collaboration Measurement of the $ t\bar{t} $ production cross section using events in the e$ \mu $ final state in pp collisions at $ \sqrt{s} = $ 13 TeV EPJC 77 (2017) 172 CMS-TOP-16-005
1611.04040
35 CMS Collaboration Particle-flow reconstruction and global event description with the CMS detector Submitted to JINST CMS-PRF-14-001
1706.04965
36 CMS Collaboration Performance of electron reconstruction and selection with the CMS detector in proton-proton collisions at $ \sqrt{s} = $ 8 TeV JINST 10 (2015) P06005
37 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
38 M. Cacciari, G. P. Salam, and G. Soyez The anti-$ k_t $ jet clustering algorithm JHEP 04 (2008) 063 0802.1189
39 M. Cacciari, G. P. Salam, and G. Soyez FastJet user manual EPJC 72 (2012) 1896 1111.6097
40 CMS Collaboration Collaboration Jet algorithms performance in 13 TeV data CMS-PAS-JME-16-003, CERN, Geneva
41 CMS Collaboration Performance of missing energy reconstruction in $ \sqrt{s}= $ 13 TeV pp collision data using the CMS detector CMS-PAS-JME-16-004 CMS-PAS-JME-16-004
42 CMS Collaboration Identification of b-quark jets with the CMS experiment JINST 8 (2013) P04013 CMS-BTV-12-001
1211.4462
43 CMS Collaboration Identification of b quark jets at the cms experiment in the lhc run2 CDS
44 J. H. Friedman Stochastic gradient boosting Computational Statistics \& Data Analysis 38 (2002), no. 4, 367, . Nonlinear Methods and Data Mining
45 H. Voss, A. Hocker, J. Stelzer, and F. Tegenfeldt TMVA, the toolkit for multivariate data analysis with ROOT in XI International Workshop on Advanced Computing and Analysis Techniques in Physics Research, p. 040 SISSA, 2007 PoS(ACAT2007)040 physics/0703039
46 ATLAS Collaboration Measurement of the Inelastic Proton-Proton Cross Section at $ \sqrt{s} = $ 13 TeV with the ATLAS Detector at the LHC PRL 117 (2016) 182002 1606.02625
47 CMS Collaboration CMS Luminosity Measurements at 13 TeV - Winter 2017 update
48 J. R. Christiansen and P. Z. Skands String Formation Beyond Leading Colour JHEP 08 (2015) 003 1505.01681
49 S. Argyropoulos and T. Sjöstrand Effects of color reconnection on $ t\bar{t} $ final states at the LHC JHEP 11 (2014) 043 1407.6653
Compact Muon Solenoid
LHC, CERN