CMS-PAS-B2G-16-017

CMS-PAS-B2G-16-017
Search for W' boson resonances decaying into a top quark and a bottom quark in the leptonic final state using data collected at $\sqrt{s}=$ 13 TeV
CMS Collaboration
July 2016

Abstract: We present a search for the production of a heavy gauge boson W' decaying into a top quark and a bottom quark. The dataset used corresponds to an integrated luminosity of 12.9 fb$^{-1}$ collected by the CMS experiment at $\sqrt{s}=$ 13 TeV during 2016. The final state signature searched for includes a lepton ($\mathrm{e}, \mu$) plus jets and missing transverse energy. We find no evidence of a W' boson and set 95% confidence level (C.L.) upper limits on its production cross-section times branching fraction. For W' bosons with purely right handed couplings, the observed (expected) 95% C.L. lower limit is 2.67 (2.70) TeV. These are currently the most stringent limits in this channel.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1-a: The reconstructed tb invariant mass distributions after the final selection for the electron (a,c) and muon (b,d), channels with 1 (a,b) and 2 (c,d) b-tagged jets. Pull is defined as the difference between data and simulation in units of the uncertainty. The hatched region represents the predicted background uncertainty. For both the pull and hatched region, uncertainties from sources which affect the shape of the distribution are not included. See section {sec:systematics} for a discussion of uncertainty sources.
png pdf	Figure 1-b: The reconstructed tb invariant mass distributions after the final selection for the electron (a,c) and muon (b,d), channels with 1 (a,b) and 2 (c,d) b-tagged jets. Pull is defined as the difference between data and simulation in units of the uncertainty. The hatched region represents the predicted background uncertainty. For both the pull and hatched region, uncertainties from sources which affect the shape of the distribution are not included. See section {sec:systematics} for a discussion of uncertainty sources.
png pdf	Figure 1-c: The reconstructed tb invariant mass distributions after the final selection for the electron (a,c) and muon (b,d), channels with 1 (a,b) and 2 (c,d) b-tagged jets. Pull is defined as the difference between data and simulation in units of the uncertainty. The hatched region represents the predicted background uncertainty. For both the pull and hatched region, uncertainties from sources which affect the shape of the distribution are not included. See section {sec:systematics} for a discussion of uncertainty sources.
png pdf	Figure 1-d: The reconstructed tb invariant mass distributions after the final selection for the electron (a,c) and muon (b,d), channels with 1 (a,b) and 2 (c,d) b-tagged jets. Pull is defined as the difference between data and simulation in units of the uncertainty. The hatched region represents the predicted background uncertainty. For both the pull and hatched region, uncertainties from sources which affect the shape of the distribution are not included. See section {sec:systematics} for a discussion of uncertainty sources.
png pdf	Figure 2-a: Expected Bayesian 95% C.L. upper limits on the production cross-section times branching fraction of right-handed W' bosons in the electron+jets channel (a) and muon+jets channel (b) for combined 1 or 2 b-tags for right-handed W' bosons. W' masses with a cross-section exceeding the observed limit are excluded. Limits have been calculated with an integrated luminosity of 12.9fb$^{-1}$. Uncertainties on the signal cross sections due to $Q^2$ scale and PDF uncertainties are shown as bands around the theory curves.
png pdf	Figure 2-b: Expected Bayesian 95% C.L. upper limits on the production cross-section times branching fraction of right-handed W' bosons in the electron+jets channel (a) and muon+jets channel (b) for combined 1 or 2 b-tags for right-handed W' bosons. W' masses with a cross-section exceeding the observed limit are excluded. Limits have been calculated with an integrated luminosity of 12.9fb$^{-1}$. Uncertainties on the signal cross sections due to $Q^2$ scale and PDF uncertainties are shown as bands around the theory curves.
png pdf	Figure 3: Expected Bayesian 95% C.L. upper limits for all channels combined on the production cross-section times branching fraction of right-handed W' bosons. W' masses with a cross-section exceeding the observed limit are excluded. Limits have been calculated with an integrated luminosity of 12.9fb$^{-1}$. Uncertainties on the signal cross sections due to $Q^2$ scale and PDF uncertainties are shown as bands around the theory curves.

Tables
png pdf	Table 1: Number of selected data and background events in the muon channel. The expectation is computed corresponding to an integrated luminosity of 12.9 fb$^{-1}$. ''Final selection'' refers to the additional cuts of $p_{T}^{top}>$ 250, $p_{T}^{jet1+jet2}>$ 350, and 250 $
png pdf	Table 2: Number of selected data and background events in the electron channel. The expectation is computed corresponding to an integrated luminosity of 12.9 fb$^{-1}$. ''Final selection'' refers to the additional cuts of $p_{T}^{top}>$ 250 and $p_{T}^{jet1+jet2}> $ 350. The quoted uncertainty does not include shape-based systematics.
png pdf	Table 3: List of systematic uncertainties taken into account in the analysis. The Pileup, Top ${p_{\mathrm {T}}}$ Reweighting and W+jets Heavy/Light Flavor systematic uncertainties are described in more detail in the text.

Summary

We have conducted a search for heavy right handed W' bosons decaying to a top and bottom quark in proton-proton collisions at $\sqrt{s}=$ 13 TeV using a subset of the data collected in 2016. We study the tb invariant mass distrubtion and find good agreement between the data and predictions from simulation. We find no evidence for W' boson production and set 95% C.L. upper limits on the production cross-section times branching fraction for W' $\rightarrow \mathrm{tb}$. Comparing our measurement to the theoretical prediction, we find an observed (expected) limit of 2.67 (2.70) TeV. These limits improve on the results from [13] are the most stringent limits to date for this decay channel.

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