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| CMS-B2G-17-010 ; CERN-EP-2017-196 | ||
| Search for heavy resonances decaying to a top quark and a bottom quark in the lepton+jets final state in proton-proton collisions at 13 TeV | ||
| CMS Collaboration | ||
| 28 August 2017 | ||
| Phys. Lett. B 777 (2017) 39 | ||
| Abstract: A search is presented for narrow heavy resonances decaying to a top quark and a bottom quark using data collected by the CMS experiment at $ \sqrt{\smash[b]{s}} = $ 13 TeV in 2016. The data set analyzed corresponds to an integrated luminosity of 35.9 fb$\smash[t]{^{-1}}$. Final states that include a single lepton (e, $\mu$), multiple jets, and missing transverse momentum are analyzed. No evidence is found for the production of a W' boson, and the production of right-handed W' bosons is excluded at 95% confidence level for masses up to 3.6 TeV depending on the scenario considered. Exclusion limits for W' bosons are also presented as a function of their coupling strength to left- and right-handed fermions. These limits on a W' boson decaying via a top and a bottom quark are the most stringent published to date. | ||
| Links: e-print arXiv:1708.08539 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
The reconstructed $ {M_{\mathrm{ t } \mathrm{ b } }} $ distributions in the 1 b tag (upper) and 2 b tags (lower) categories, for the electron (left) and muon (right) channels, for Type A events. Distributions for $ \mathrm{W}'_{\text{R}} $ bosons with masses of 2, 2.5, and 3 TeV are shown. The distribution is shown after the application of all selections. The background uncertainty includes both statistical and systematic components, while "Tot. unc." in the lower panels corresponds to the combined uncertainty of the background prediction and data. |
png pdf |
Figure 1-a:
The reconstructed $ {M_{\mathrm{ t } \mathrm{ b } }} $ distribution in the 1 b tag category, for the electron channel, for Type A events. Distributions for $ \mathrm{W}'_{\text{R}} $ bosons with masses of 2, 2.5, and 3 TeV are shown. The distribution is shown after the application of all selections. The background uncertainty includes both statistical and systematic components, while "Tot. unc." in the lower panels corresponds to the combined uncertainty of the background prediction and data. |
png pdf |
Figure 1-b:
The reconstructed $ {M_{\mathrm{ t } \mathrm{ b } }} $ distribution in the 1 b tag category, for the muon channel, for Type A events. Distributions for $ \mathrm{W}'_{\text{R}} $ bosons with masses of 2, 2.5, and 3 TeV are shown. The distribution is shown after the application of all selections. The background uncertainty includes both statistical and systematic components, while "Tot. unc." in the lower panels corresponds to the combined uncertainty of the background prediction and data. |
png pdf |
Figure 1-c:
The reconstructed $ {M_{\mathrm{ t } \mathrm{ b } }} $ distribution in the 2 b tags category, for the electron channel, for Type A events. Distributions for $ \mathrm{W}'_{\text{R}} $ bosons with masses of 2, 2.5, and 3 TeV are shown. The distribution is shown after the application of all selections. The background uncertainty includes both statistical and systematic components, while "Tot. unc." in the lower panels corresponds to the combined uncertainty of the background prediction and data. |
png pdf |
Figure 1-d:
The reconstructed $ {M_{\mathrm{ t } \mathrm{ b } }} $ distribution in the 2 b tags category, for the muon channel, for Type A events. Distributions for $ \mathrm{W}'_{\text{R}} $ bosons with masses of 2, 2.5, and 3 TeV are shown. The distribution is shown after the application of all selections. The background uncertainty includes both statistical and systematic components, while "Tot. unc." in the lower panels corresponds to the combined uncertainty of the background prediction and data. |
png pdf |
Figure 2:
The reconstructed $ {M_{\mathrm{ t } \mathrm{ b } }} $ distributions in the 1 b tag (upper) and 2 b tags (lower) categories, for the electron (left) and muon (right) channels, for Type B events. Distributions for $ \mathrm{W}'_{\text{R}} $ bosons with masses of 2, 2.5, and 3 TeV are shown. The distribution is shown after the application of all selections. The background uncertainty includes both statistical and systematic components, while "Tot. unc." in the lower panels corresponds to the combined uncertainty of the background prediction and data. |
png pdf |
Figure 2-a:
The reconstructed $ {M_{\mathrm{ t } \mathrm{ b } }} $ distribution in the 1 b tag category, for the electron channel, for Type B events. Distributions for $ \mathrm{W}'_{\text{R}} $ bosons with masses of 2, 2.5, and 3 TeV are shown. The distribution is shown after the application of all selections. The background uncertainty includes both statistical and systematic components, while "Tot. unc." in the lower panels corresponds to the combined uncertainty of the background prediction and data. |
png pdf |
Figure 2-b:
The reconstructed $ {M_{\mathrm{ t } \mathrm{ b } }} $ distribution in the 1 b tag category, for the muon channel, for Type B events. Distributions for $ \mathrm{W}'_{\text{R}} $ bosons with masses of 2, 2.5, and 3 TeV are shown. The distribution is shown after the application of all selections. The background uncertainty includes both statistical and systematic components, while "Tot. unc." in the lower panels corresponds to the combined uncertainty of the background prediction and data. |
png pdf |
Figure 2-c:
The reconstructed $ {M_{\mathrm{ t } \mathrm{ b } }} $ distribution in the 2 b tags category, for the electron channel, for Type B events. Distributions for $ \mathrm{W}'_{\text{R}} $ bosons with masses of 2, 2.5, and 3 TeV are shown. The distribution is shown after the application of all selections. The background uncertainty includes both statistical and systematic components, while "Tot. unc." in the lower panels corresponds to the combined uncertainty of the background prediction and data. |
png pdf |
Figure 2-d:
The reconstructed $ {M_{\mathrm{ t } \mathrm{ b } }} $ distribution in the 2 b tags category, for the muon channel, for Type B events. Distributions for $ \mathrm{W}'_{\text{R}} $ bosons with masses of 2, 2.5, and 3 TeV are shown. The distribution is shown after the application of all selections. The background uncertainty includes both statistical and systematic components, while "Tot. unc." in the lower panels corresponds to the combined uncertainty of the background prediction and data. |
png pdf |
Figure 3:
Upper limit at 95% CL on the $ \mathrm{W}'_{\text{R}} $ boson production cross section separately in the electron (left ) and muon (right ) channels. Signal masses for which the theoretical cross section (in red and blue for $M_{\nu _\mathrm {R}}\ll M_{\mathrm{W}'_{\text{R}}}$ and $M_{\nu _\mathrm {R}}>M_{\mathrm{W}'_{\text{R}}}$, respectively) exceeds the observed upper limit (in solid black) are excluded at 95% CL. The green and yellow bands represent the $\pm $1 and 2 s.d. uncertainties in the expected limit, respectively. |
png pdf |
Figure 3-a:
Upper limit at 95% CL on the $ \mathrm{W}'_{\text{R}} $ boson production cross section in the electron channel. Signal masses for which the theoretical cross section (in red and blue for $M_{\nu _\mathrm {R}}\ll M_{\mathrm{W}'_{\text{R}}}$ and $M_{\nu _\mathrm {R}}>M_{\mathrm{W}'_{\text{R}}}$, respectively) exceeds the observed upper limit (in solid black) are excluded at 95% CL. The green and yellow bands represent the $\pm $1 and 2 s.d. uncertainties in the expected limit, respectively. |
png pdf |
Figure 3-b:
Upper limit at 95% CL on the $ \mathrm{W}'_{\text{R}} $ boson production cross section in the muon channel. Signal masses for which the theoretical cross section (in red and blue for $M_{\nu _\mathrm {R}}\ll M_{\mathrm{W}'_{\text{R}}}$ and $M_{\nu _\mathrm {R}}>M_{\mathrm{W}'_{\text{R}}}$, respectively) exceeds the observed upper limit (in solid black) are excluded at 95% CL. The green and yellow bands represent the $\pm $1 and 2 s.d. uncertainties in the expected limit, respectively. |
png pdf |
Figure 4:
Upper limit at 95% CL on the $ \mathrm{W}'_{\text{R}} $ boson production cross section for the combined electron and muon channels. Signal masses for which the theoretical cross section (in red and blue for $M_{\nu _\mathrm {R}}\ll M_{\mathrm{W}'_{\text{R}}}$ and $M_{\nu _\mathrm {R}} > M_{\mathrm{W}'_{\text{R}}}$, respectively) exceeds the observed upper limit (in solid black) are excluded at 95% CL. The green and yellow bands represent the $\pm $1 and 2 s.d. uncertainties in the expected limit, respectively. |
png pdf |
Figure 5:
Expected (left ) and observed (right ) limits on the W' boson mass as function of the left-handed ($a_\mathrm {L}$) and right-handed ($a_\mathrm {R}$) couplings. Black lines represent contours of equal W' boson mass. |
png pdf |
Figure 5-a:
Expected limits on the W' boson mass as function of the left-handed ($a_\mathrm {L}$) and right-handed ($a_\mathrm {R}$) couplings. Black lines represent contours of equal W' boson mass. |
png pdf |
Figure 5-b:
Observed limits on the W' boson mass as function of the left-handed ($a_\mathrm {L}$) and right-handed ($a_\mathrm {R}$) couplings. Black lines represent contours of equal W' boson mass. |
| Tables | |
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Table 1:
Observed and expected event yields from all the background processes and $ \mathrm{W}'_{\text{R}} $ bosons with three different masses. HF and LF indicate heavy flavor and light flavor events, respectively. Yields are separated into 8 event categories by the lepton type (e or $\mu $), number of b tags (1 or 2), and $ {p_{\mathrm {T}}} ^{\mathrm{ t } }$ and $ {p_{\mathrm {T}}} ^\mathrm {j_1+j_2}$ (Type A or B). The uncertainty in the total expected background includes both the systematic and statistical sources. |
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Table 2:
List of systematic uncertainties taken into account in the analysis. For sources that affect the shape of the $ {M_{\mathrm{ t } \mathrm{ b } }} $ distribution the given rate uncertainty is approximate. The pileup, top quark $ {p_{\mathrm {T}}} $ reweighting, and W+jets heavy/light flavor systematic uncertainties are described in more detail in the text. A check mark in the "Signal" column indicates that the uncertainty is also applied to the signal samples. For the PDF uncertainty, only its shape component is included for signal samples. |
| Summary |
| A search for a narrow heavy W' boson resonance decaying to a top quark and a bottom quark has been performed in lepton+jets final states using data collected at $ \sqrt{\smash[b]{s}} = $ 13 TeV by the CMS detector in 2016, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. No evidence is observed for the production of a W' boson, and 95% CL upper limits on the product of the right-handed W' ($\mathrm{W}'_{\text{R}})$ boson production cross section and its branching fraction to a top and a bottom quark are calculated as a function of the $\mathrm{W}'_{\text{R}}$ boson mass. The observed (expected) 95% CL upper limit is 3.4 (3.3) TeV if $M_{\mathrm{W}'_R} \gg M_{\nu_\mathrm{R}} $ and 3.6 (3.5) TeV if $ M_{\mathrm{W}'_R} < M_{\nu_\mathrm{R}} $, where $ M_{\nu_\mathrm{R}} $ is the mass of the right-handed neutrino. Exclusion limits are also presented for W' bosons with varied left- and right-handed couplings to fermions, for the first time at $ \sqrt{\smash[b]{s}}= $ 13 TeV. These results are the most stringent limits to date on the production of W' bosons that decay to a top and a bottom quark. |
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Compact Muon Solenoid LHC, CERN |
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