CMS-PAS-TOP-16-004

CMS-PAS-TOP-16-004
Measurement of the differential cross section for $t$-channel single-top-quark production at $\sqrt{s}=$ 13 TeV
CMS Collaboration
May 2016

Abstract: A measurement of differential cross sections for $t$-channel single-top-quark production in proton-proton collisions at a centre-of-mass energy of 13 TeV is presented. The cross sections are measured as functions of the transverse momentum and the absolute value of the rapidity of the top quark. The analyzed data were recorded in the year 2015 by the CMS experiment and correspond to an integrated luminosity of 2.3 fb$^{-1}$. A maximum-likelihood fit to a multivariate discriminator is used to infer the signal and background fractions from the data. Unfolding to parton level is performed. The measured cross sections are compared with theoretical predictions to next-to-leading order matched with parton showering as implemented in Monte Carlo generators. General agreement is found within uncertainties.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ;

Figures	Summary	References	CMS Publications

Figures
png pdf	Figure 1-a: Born-level Feynman diagrams for single top quark production in the $t$ channel: (a) (2)$\rightarrow $(2) and (b) (2)$\rightarrow $(3) processes. Corresponding diagrams exist for single-top-antiquark production.
png pdf	Figure 1-b: Born-level Feynman diagrams for single top quark production in the $t$ channel: (a) (2)$\rightarrow $(2) and (b) (2)$\rightarrow $(3) processes. Corresponding diagrams exist for single-top-antiquark production.
png pdf	Figure 2-a: Distributions of discriminating observables used in the BDT training: (a) the absolute value of the pseudorapidity of the non-tagged jet; (b) the mass of the reconstructed top quark candidate; (c) the $\Delta R$ distance between the two selected jets; (d) the absolute difference in pseudorapidity between the b-tagged jet and the selected muon. The simulations of the different processes are normalized to the inclusive ML fit result. The ratio of yields in data and simulation is displayed under the histograms. The hatched band denotes the total systematic uncertainty scaled to the fit results. The first and last bin includes the under- and overflow of events, respectively.
png pdf	Figure 2-b: Distributions of discriminating observables used in the BDT training: (a) the absolute value of the pseudorapidity of the non-tagged jet; (b) the mass of the reconstructed top quark candidate; (c) the $\Delta R$ distance between the two selected jets; (d) the absolute difference in pseudorapidity between the b-tagged jet and the selected muon. The simulations of the different processes are normalized to the inclusive ML fit result. The ratio of yields in data and simulation is displayed under the histograms. The hatched band denotes the total systematic uncertainty scaled to the fit results. The first and last bin includes the under- and overflow of events, respectively.
png pdf	Figure 2-c: Distributions of discriminating observables used in the BDT training: (a) the absolute value of the pseudorapidity of the non-tagged jet; (b) the mass of the reconstructed top quark candidate; (c) the $\Delta R$ distance between the two selected jets; (d) the absolute difference in pseudorapidity between the b-tagged jet and the selected muon. The simulations of the different processes are normalized to the inclusive ML fit result. The ratio of yields in data and simulation is displayed under the histograms. The hatched band denotes the total systematic uncertainty scaled to the fit results. The first and last bin includes the under- and overflow of events, respectively.
png pdf	Figure 2-d: Distributions of discriminating observables used in the BDT training: (a) the absolute value of the pseudorapidity of the non-tagged jet; (b) the mass of the reconstructed top quark candidate; (c) the $\Delta R$ distance between the two selected jets; (d) the absolute difference in pseudorapidity between the b-tagged jet and the selected muon. The simulations of the different processes are normalized to the inclusive ML fit result. The ratio of yields in data and simulation is displayed under the histograms. The hatched band denotes the total systematic uncertainty scaled to the fit results. The first and last bin includes the under- and overflow of events, respectively.
png pdf	Figure 3-a: Distributions of the fit variables: (a) the transverse W boson mass distribution and (b) the BDT discriminant after selecting only events with $ {m_{\mathrm {T}}(\mathrm {W})} >$ 50 GeV. The simulations of the different processes are normalized to the inclusive ML fit result. The ratio of yields in data and simulation is displayed under the histograms. The hatched band denotes the total systematic uncertainty scaled to the fit results. The first and last bin includes the under- and overflow of events, respectively.
png pdf	Figure 3-b: Distributions of the fit variables: (a) the transverse W boson mass distribution and (b) the BDT discriminant after selecting only events with $ {m_{\mathrm {T}}(\mathrm {W})} >$ 50 GeV. The simulations of the different processes are normalized to the inclusive ML fit result. The ratio of yields in data and simulation is displayed under the histograms. The hatched band denotes the total systematic uncertainty scaled to the fit results. The first and last bin includes the under- and overflow of events, respectively.
png pdf	Figure 4-a: Distributions of (a,b) the transverse momentum and (c,d) the rapidity of the reconstructed top quark in 2j1t for events with $ {m_{\mathrm {T}}(\mathrm {W})} >$ 50 GeV: (a,c) signal-depleted region ($\mathrm {BDT}< $ 0), (b,d) signal-enhanced region($\mathrm {BDT}> $ 0.6). The simulations of the different processes are normalized to the inclusive ML fit result. The ratio of yields in data and simulation is displayed under the histograms. The hatched band denotes the total systematic uncertainty scaled to the fit results. The average number of events per bin is normalized to the bin width. The first and last bin includes the under- and overflow of events, respectively.
png pdf	Figure 4-b: Distributions of (a,b) the transverse momentum and (c,d) the rapidity of the reconstructed top quark in 2j1t for events with $ {m_{\mathrm {T}}(\mathrm {W})} >$ 50 GeV: (a,c) signal-depleted region ($\mathrm {BDT}< $ 0), (b,d) signal-enhanced region($\mathrm {BDT}> $ 0.6). The simulations of the different processes are normalized to the inclusive ML fit result. The ratio of yields in data and simulation is displayed under the histograms. The hatched band denotes the total systematic uncertainty scaled to the fit results. The average number of events per bin is normalized to the bin width. The first and last bin includes the under- and overflow of events, respectively.
png pdf	Figure 4-c: Distributions of (a,b) the transverse momentum and (c,d) the rapidity of the reconstructed top quark in 2j1t for events with $ {m_{\mathrm {T}}(\mathrm {W})} >$ 50 GeV: (a,c) signal-depleted region ($\mathrm {BDT}< $ 0), (b,d) signal-enhanced region($\mathrm {BDT}> $ 0.6). The simulations of the different processes are normalized to the inclusive ML fit result. The ratio of yields in data and simulation is displayed under the histograms. The hatched band denotes the total systematic uncertainty scaled to the fit results. The average number of events per bin is normalized to the bin width. The first and last bin includes the under- and overflow of events, respectively.
png pdf	Figure 4-d: Distributions of (a,b) the transverse momentum and (c,d) the rapidity of the reconstructed top quark in 2j1t for events with $ {m_{\mathrm {T}}(\mathrm {W})} >$ 50 GeV: (a,c) signal-depleted region ($\mathrm {BDT}< $ 0), (b,d) signal-enhanced region($\mathrm {BDT}> $ 0.6). The simulations of the different processes are normalized to the inclusive ML fit result. The ratio of yields in data and simulation is displayed under the histograms. The hatched band denotes the total systematic uncertainty scaled to the fit results. The average number of events per bin is normalized to the bin width. The first and last bin includes the under- and overflow of events, respectively.
png pdf	Figure 5-a: Measured differential cross section of $t$-channel single top quark production as a function of the top quark (a) transverse momentum and (b) rapidity. Horizontal ticks on the error bars indicate the statistical uncertainty and vertical bars indicate the total uncertainty per bin.
png pdf	Figure 5-b: Measured differential cross section of $t$-channel single top quark production as a function of the top quark (a) transverse momentum and (b) rapidity. Horizontal ticks on the error bars indicate the statistical uncertainty and vertical bars indicate the total uncertainty per bin.

Summary

The differential cross section of t-channel production of single top quarks has been measured as a function of the transverse momentum and rapidity of the top quark using a dataset corresponding to a total integrated luminosity of 2.3 fb$^{-1}$ at $\sqrt{s} =$ 13 TeV, collected with the CMS detector. Within the experimental uncertainties, no significant deviation is observed with respect to the theoretical predictions based on NLO+PS generators in the 4FS or 5FS.

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