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| CMS-B2G-19-005 ; CERN-EP-2020-154 | ||
| A search for bottom-type, vector-like quark pair production in a fully hadronic final state in proton-proton collisions at $\sqrt{s} = $ 13 TeV | ||
| CMS Collaboration | ||
| 22 August 2020 | ||
| Phys. Rev. D 102 (2020) 112004 | ||
| Abstract: A search is described for the production of a pair of bottom-type vector-like quarks (VLQs), each decaying into a $\mathrm{b}$ or $\mathrm{\bar{b}}$ quark and either a Higgs or a Z boson, with a mass greater than 1000 GeV. The analysis is based on data from proton-proton collisions at a 13 TeV center-of-mass energy recorded at the CERN LHC, corresponding to a total integrated luminosity of 137 fb$^{-1}$. As the predominant decay modes of the Higgs and Z bosons are to a pair of quarks, the analysis focuses on final states consisting of jets resulting from the six quarks produced in the events. Since the two jets produced in the decay of a highly Lorentz-boosted Higgs or Z boson can merge to form a single jet, nine independent analyses are performed, categorized by the number of observed jets and the reconstructed event mode. No signal in excess of the expected background is observed. Lower limits are set on the VLQ mass at 95% confidence level equal to 1570 GeV in the case where the VLQ decays exclusively to a b quark and a Higgs boson, 1390 GeV for when it decays exclusively to a b quark and a Z boson, and 1450 GeV for when it decays equally in these two modes. These limits represent significant improvements over the previously published VLQ limits. | ||
| Links: e-print arXiv:2008.09835 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
Dominant diagrams of the pair production of bottom-type VLQs ($\mathrm{B}$) that subsequently decay to a $\mathrm{b}$ or $\mathrm{\bar{b}}$ quark and either a Higgs or Z boson. In events targeted by this analysis, the Z boson then decays to a pair of quarks, where $\mathrm{q}$ denotes any quark other than a top quark, while the Higgs boson decays to $\mathrm{b}$ quarks. Upper left: ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ mode, upper right: ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ mode, lower: ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ mode. |
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Figure 2:
Distributions of ${m_\text {VLQ}}$ for simulated signal events with a generated VLQ mass $m_{\mathrm{B}} = $ 1200 GeV. A requirement of $ {\chi ^2_\text {mod}/\text {ndf}} < $ 2 is applied to the events. Mass distributions for 4-jet (left), 5-jet (center), and 6-jet (right) events are shown for the three event modes: ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ (upper row), ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ (middle row), and ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ (lower row). |
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Figure 2-a:
Distribution of ${m_\text {VLQ}}$ for simulated 4-jet signal events with a generated VLQ mass $m_{\mathrm{B}} = $ 1200 GeV, for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ event mode. A requirement of $ {\chi ^2_\text {mod}/\text {ndf}} < $ 2 is applied to the events. |
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Figure 2-b:
Distribution of ${m_\text {VLQ}}$ for simulated 5-jet signal events with a generated VLQ mass $m_{\mathrm{B}} = $ 1200 GeV, for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ event mode. A requirement of $ {\chi ^2_\text {mod}/\text {ndf}} < $ 2 is applied to the events. |
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Figure 2-c:
Distribution of ${m_\text {VLQ}}$ for simulated 6-jet signal events with a generated VLQ mass $m_{\mathrm{B}} = $ 1200 GeV, for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ event mode. A requirement of $ {\chi ^2_\text {mod}/\text {ndf}} < $ 2 is applied to the events. |
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Figure 2-d:
Distribution of ${m_\text {VLQ}}$ for simulated 4-jet signal events with a generated VLQ mass $m_{\mathrm{B}} = $ 1200 GeV, for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ event mode. A requirement of $ {\chi ^2_\text {mod}/\text {ndf}} < $ 2 is applied to the events. |
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Figure 2-e:
Distribution of ${m_\text {VLQ}}$ for simulated 5-jet signal events with a generated VLQ mass $m_{\mathrm{B}} = $ 1200 GeV, for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ event mode. A requirement of $ {\chi ^2_\text {mod}/\text {ndf}} < $ 2 is applied to the events. |
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Figure 2-f:
Distribution of ${m_\text {VLQ}}$ for simulated 6-jet signal events with a generated VLQ mass $m_{\mathrm{B}} = $ 1200 GeV, for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ event mode. A requirement of $ {\chi ^2_\text {mod}/\text {ndf}} < $ 2 is applied to the events. |
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Figure 2-g:
Distribution of ${m_\text {VLQ}}$ for simulated 4-jet signal events with a generated VLQ mass $m_{\mathrm{B}} = $ 1200 GeV, for the ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. A requirement of $ {\chi ^2_\text {mod}/\text {ndf}} < $ 2 is applied to the events. |
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Figure 2-h:
Distribution of ${m_\text {VLQ}}$ for simulated 5-jet signal events with a generated VLQ mass $m_{\mathrm{B}} = $ 1200 GeV, for the ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. A requirement of $ {\chi ^2_\text {mod}/\text {ndf}} < $ 2 is applied to the events. |
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Figure 2-i:
Distribution of ${m_\text {VLQ}}$ for simulated 6-jet signal events with a generated VLQ mass $m_{\mathrm{B}} = $ 1200 GeV, for the ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. A requirement of $ {\chi ^2_\text {mod}/\text {ndf}} < $ 2 is applied to the events. |
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Figure 3:
Distribution of ${\chi ^2_\text {mod}/\text {ndf}}$ for the best jet combination for simulated 1200 GeV VLQ events (red histogram) and data (black points), for 4-jet (left), 5-jet (center), and 6-jet events (right). The simulated signal events and data events are normalized to the same integral value within the displayed ${\chi ^2_\text {mod}}$ range. |
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Figure 3-a:
Distribution of ${\chi ^2_\text {mod}/\text {ndf}}$ for the best jet combination for simulated 1200 GeV VLQ events (red histogram) and data (black points), for 4-jet events. The simulated signal events and data events are normalized to the same integral value within the displayed ${\chi ^2_\text {mod}}$ range. |
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Figure 3-b:
Distribution of ${\chi ^2_\text {mod}/\text {ndf}}$ for the best jet combination for simulated 1200 GeV VLQ events (red histogram) and data (black points), for 5-jet events. The simulated signal events and data events are normalized to the same integral value within the displayed ${\chi ^2_\text {mod}}$ range. |
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Figure 3-c:
Distribution of ${\chi ^2_\text {mod}/\text {ndf}}$ for the best jet combination for simulated 1200 GeV VLQ events (red histogram) and data (black points), for 6-jet events. The simulated signal events and data events are normalized to the same integral value within the displayed ${\chi ^2_\text {mod}}$ range. |
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Figure 4:
Distributions of ${m_\text {VLQ}}$ for the jet combination with the lowest ${\chi ^2_\text {mod}}$ in 4-jet (left), 5-jet (center), and 6-jet (right) multiplicity events. The red lines show the exponential fit in the range 1000-2000 GeV. The lower panels show the fractional difference, $(\text {data}-\text {fit})/\text {fit}$. |
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Figure 4-a:
Distribution of ${m_\text {VLQ}}$ for the jet combination with the lowest ${\chi ^2_\text {mod}}$ in 4-jet multiplicity events. The red lines show the exponential fit in the range 1000-2000 GeV. The lower panel shows the fractional difference, $(\text {data}-\text {fit})/\text {fit}$. |
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Figure 4-b:
Distribution of ${m_\text {VLQ}}$ for the jet combination with the lowest ${\chi ^2_\text {mod}}$ in 5-jet multiplicity events. The red lines show the exponential fit in the range 1000-2000 GeV. The lower panel shows the fractional difference, $(\text {data}-\text {fit})/\text {fit}$. |
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Figure 4-c:
Distribution of ${m_\text {VLQ}}$ for the jet combination with the lowest ${\chi ^2_\text {mod}}$ in 6-jet multiplicity events. The red lines show the exponential fit in the range 1000-2000 GeV. The lower panel shows the fractional difference, $(\text {data}-\text {fit})/\text {fit}$. |
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Figure 5:
Dependence of the BJTF on ${m_\text {VLQ}}$ in the control region 12 $ < {\chi ^2_\text {mod}/\text {ndf}} < $ 48, for 4-jet (left column), 5-jet (center column), and 6-jet (right column) multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ (upper row), ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ (middle row), and ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ (lower row) event modes. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 5-a:
Dependence of the BJTF on ${m_\text {VLQ}}$ in the control region 12 $ < {\chi ^2_\text {mod}/\text {ndf}} < $ 48, for 4-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ event mode. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 5-b:
Dependence of the BJTF on ${m_\text {VLQ}}$ in the control region 12 $ < {\chi ^2_\text {mod}/\text {ndf}} < $ 48, for 5-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ event mode. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 5-c:
Dependence of the BJTF on ${m_\text {VLQ}}$ in the control region 12 $ < {\chi ^2_\text {mod}/\text {ndf}} < $ 48, for 6-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ event mode. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 5-d:
Dependence of the BJTF on ${m_\text {VLQ}}$ in the control region 12 $ < {\chi ^2_\text {mod}/\text {ndf}} < $ 48, for 4-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ event mode. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 5-e:
Dependence of the BJTF on ${m_\text {VLQ}}$ in the control region 12 $ < {\chi ^2_\text {mod}/\text {ndf}} < $ 48, for 5-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ event mode. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 5-f:
Dependence of the BJTF on ${m_\text {VLQ}}$ in the control region 12 $ < {\chi ^2_\text {mod}/\text {ndf}} < $ 48, for 6-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ event mode. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 5-g:
Dependence of the BJTF on ${m_\text {VLQ}}$ in the control region 12 $ < {\chi ^2_\text {mod}/\text {ndf}} < $ 48, for 4-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ event mode. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 5-h:
Dependence of the BJTF on ${m_\text {VLQ}}$ in the control region 12 $ < {\chi ^2_\text {mod}/\text {ndf}} < $ 48, for 5-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ event mode. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 5-i:
Dependence of the BJTF on ${m_\text {VLQ}}$ in the control region 12 $ < {\chi ^2_\text {mod}/\text {ndf}} < $ 48, for 6-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ event mode. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 6:
Dependence of the BJTF on ${\chi ^2_\text {mod}/\text {ndf}}$ in the low-mass (500-800 GeV) VLQ region, for 4-jet (left column), 5-jet (center column), and 6-jet (right column) multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ (upper row), ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ (middle row), and ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ (lower row) event modes. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 6-a:
Dependence of the BJTF on ${\chi ^2_\text {mod}/\text {ndf}}$ in the low-mass (500-800 GeV) VLQ region, for 4-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ event mode. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 6-b:
Dependence of the BJTF on ${\chi ^2_\text {mod}/\text {ndf}}$ in the low-mass (500-800 GeV) VLQ region, for 5-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ event mode. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 6-c:
Dependence of the BJTF on ${\chi ^2_\text {mod}/\text {ndf}}$ in the low-mass (500-800 GeV) VLQ region, for 6-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ event mode. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 6-d:
Dependence of the BJTF on ${\chi ^2_\text {mod}/\text {ndf}}$ in the low-mass (500-800 GeV) VLQ region, for 4-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ event mode. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 6-e:
Dependence of the BJTF on ${\chi ^2_\text {mod}/\text {ndf}}$ in the low-mass (500-800 GeV) VLQ region, for 5-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ event mode. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 6-f:
Dependence of the BJTF on ${\chi ^2_\text {mod}/\text {ndf}}$ in the low-mass (500-800 GeV) VLQ region, for 6-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ event mode. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 6-g:
Dependence of the BJTF on ${\chi ^2_\text {mod}/\text {ndf}}$ in the low-mass (500-800 GeV) VLQ region, for 4-jet multiplicities, and for the ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 6-h:
Dependence of the BJTF on ${\chi ^2_\text {mod}/\text {ndf}}$ in the low-mass (500-800 GeV) VLQ region, for 5-jet multiplicities, and for the ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 6-i:
Dependence of the BJTF on ${\chi ^2_\text {mod}/\text {ndf}}$ in the low-mass (500-800 GeV) VLQ region, for 6-jet multiplicities, and for the ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. The data are shown as black points with vertical error bars, and the linear fit and associated uncertainty are shown as a solid red line and the shaded red band. |
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Figure 7:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in data events, for 4-jet (left column), 5-jet (center column), and 6-jet (right column) multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ (upper row), ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ (middle row), and ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ (lower row) event modes. The red box indicates the signal region, which is excluded from these plots. |
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Figure 7-a:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in data events, for 4-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. The red box indicates the signal region, which is excluded from these plots. |
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Figure 7-b:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in data events, for 5-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. The red box indicates the signal region, which is excluded from these plots. |
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Figure 7-c:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in data events, for 6-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. The red box indicates the signal region, which is excluded from these plots. |
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Figure 7-d:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in data events, for 4-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. The red box indicates the signal region, which is excluded from these plots. |
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Figure 7-e:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in data events, for 5-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. The red box indicates the signal region, which is excluded from these plots. |
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Figure 7-f:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in data events, for 6-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. The red box indicates the signal region, which is excluded from these plots. |
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Figure 7-g:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in data events, for 4-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. The red box indicates the signal region, which is excluded from these plots. |
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Figure 7-h:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in data events, for 5-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. The red box indicates the signal region, which is excluded from these plots. |
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Figure 7-i:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in data events, for 6-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. The red box indicates the signal region, which is excluded from these plots. |
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Figure 8:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in simulated VLQ signal events with $m_{\mathrm{B}} = $ 1200 GeV, for 4-jet (left column), 5-jet (center column), and 6-jet (right column) multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ (upper row), ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ (middle row), and ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ (lower row) event modes. The red box indicates the signal region. |
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Figure 8-a:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in simulated VLQ signal events with $m_{\mathrm{B}} = $ 1200 GeV, for 4-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ event mode. The red box indicates the signal region. |
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Figure 8-b:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in simulated VLQ signal events with $m_{\mathrm{B}} = $ 1200 GeV, for 5-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ event mode. The red box indicates the signal region. |
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Figure 8-c:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in simulated VLQ signal events with $m_{\mathrm{B}} = $ 1200 GeV, for 6-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ event mode. The red box indicates the signal region. |
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Figure 8-d:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in simulated VLQ signal events with $m_{\mathrm{B}} = $ 1200 GeV, for 4-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ event mode. The red box indicates the signal region. |
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Figure 8-e:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in simulated VLQ signal events with $m_{\mathrm{B}} = $ 1200 GeV, for 5-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ event mode. The red box indicates the signal region. |
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Figure 8-f:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in simulated VLQ signal events with $m_{\mathrm{B}} = $ 1200 GeV, for 6-jet multiplicities, and for the ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ event mode. The red box indicates the signal region. |
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Figure 8-g:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in simulated VLQ signal events with $m_{\mathrm{B}} = $ 1200 GeV, for 4-jet multiplicities, and for the ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. The red box indicates the signal region. |
png pdf |
Figure 8-h:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in simulated VLQ signal events with $m_{\mathrm{B}} = $ 1200 GeV, for 5-jet multiplicities, and for the ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. The red box indicates the signal region. |
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Figure 8-i:
Dependence of the BJTF on ${m_\text {VLQ}}$ and the best ${\chi ^2_\text {mod}/\text {ndf}}$ in simulated VLQ signal events with $m_{\mathrm{B}} = $ 1200 GeV, for 6-jet multiplicities, and for the ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. The red box indicates the signal region. |
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Figure 9:
Data (black points), expected background (solid blue histogram), and expected background plus a VLQ signal for different VLQ masses (colored lines), for 4-jet (left column), 5-jet (center column), and 6-jet (right column) multiplicities and for ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ (upper row), ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ (middle row), and ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ (lower row) event modes. For the signal, $ {\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{H})} = $ 100% is assumed. The hatched regions for the background and background plus signal distributions indicate the systematic uncertainties. All three data-taking years are combined. |
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Figure 9-a:
Data (black points), expected background (solid blue histogram), and expected background plus a VLQ signal for different VLQ masses (colored lines), for 4-jet multiplicities and for ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ event mode. For the signal, $ {\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{H})} = $ 100% is assumed. The hatched regions for the background and background plus signal distributions indicate the systematic uncertainties. All three data-taking years are combined. |
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Figure 9-b:
Data (black points), expected background (solid blue histogram), and expected background plus a VLQ signal for different VLQ masses (colored lines), for 5-jet multiplicities and for ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ event mode. For the signal, $ {\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{H})} = $ 100% is assumed. The hatched regions for the background and background plus signal distributions indicate the systematic uncertainties. All three data-taking years are combined. |
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Figure 9-c:
Data (black points), expected background (solid blue histogram), and expected background plus a VLQ signal for different VLQ masses (colored lines), for 6-jet multiplicities and for ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{H}}$ event mode. For the signal, $ {\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{H})} = $ 100% is assumed. The hatched regions for the background and background plus signal distributions indicate the systematic uncertainties. All three data-taking years are combined. |
png pdf |
Figure 9-d:
Data (black points), expected background (solid blue histogram), and expected background plus a VLQ signal for different VLQ masses (colored lines), for 4-jet multiplicities and for ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ event mode. For the signal, $ {\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{H})} = $ 100% is assumed. The hatched regions for the background and background plus signal distributions indicate the systematic uncertainties. All three data-taking years are combined. |
png pdf |
Figure 9-e:
Data (black points), expected background (solid blue histogram), and expected background plus a VLQ signal for different VLQ masses (colored lines), for 5-jet multiplicities and for ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ event mode. For the signal, $ {\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{H})} = $ 100% is assumed. The hatched regions for the background and background plus signal distributions indicate the systematic uncertainties. All three data-taking years are combined. |
png pdf |
Figure 9-f:
Data (black points), expected background (solid blue histogram), and expected background plus a VLQ signal for different VLQ masses (colored lines), for 6-jet multiplicities and for ${\mathrm{b} \mathrm{H} \mathrm{b} \mathrm{Z}}$ event mode. For the signal, $ {\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{H})} = $ 100% is assumed. The hatched regions for the background and background plus signal distributions indicate the systematic uncertainties. All three data-taking years are combined. |
png pdf |
Figure 9-g:
Data (black points), expected background (solid blue histogram), and expected background plus a VLQ signal for different VLQ masses (colored lines), for 4-jet multiplicities and for ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. For the signal, $ {\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{H})} = $ 100% is assumed. The hatched regions for the background and background plus signal distributions indicate the systematic uncertainties. All three data-taking years are combined. |
png pdf |
Figure 9-h:
Data (black points), expected background (solid blue histogram), and expected background plus a VLQ signal for different VLQ masses (colored lines), for 5-jet multiplicities and for ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. For the signal, $ {\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{H})} = $ 100% is assumed. The hatched regions for the background and background plus signal distributions indicate the systematic uncertainties. All three data-taking years are combined. |
png pdf |
Figure 9-i:
Data (black points), expected background (solid blue histogram), and expected background plus a VLQ signal for different VLQ masses (colored lines), for 6-jet multiplicities and for ${\mathrm{b} \mathrm{Z} \mathrm{b} \mathrm{Z}}$ event mode. For the signal, $ {\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{H})} = $ 100% is assumed. The hatched regions for the background and background plus signal distributions indicate the systematic uncertainties. All three data-taking years are combined. |
png pdf |
Figure 10:
Expected (upper) and observed (lower) limits on the VLQ mass at 95% CL as a function of the branching fractions ${\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{H})}$ and ${\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{Z})}$. |
png pdf |
Figure 10-a:
Expected limit on the VLQ mass at 95% CL as a function of the branching fractions ${\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{H})}$ and ${\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{Z})}$. |
png pdf |
Figure 10-b:
Observed limit on the VLQ mass at 95% CL as a function of the branching fractions ${\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{H})}$ and ${\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{Z})}$. |
png pdf |
Figure 11:
The 95% confidence limit on the cross section for VLQ pair production as a function of VLQ mass for three branching fraction hypotheses: $ {\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{H})} = $ 100% (upper left), $ {\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{Z})} = $ 100% (upper right), and $ {\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{H})} = {\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{Z})} = $ 50% (lower). The solid black line indicates the observed limit and the dashed line indicates the expected limit with 1 sigma (green band) and 2 sigma (yellow band) uncertainties. The theoretical cross section and its uncertainty are shown as the red line and pale red band; the band is only slightly visible outside the line. |
png pdf |
Figure 11-a:
The 95% confidence limit on the cross section for VLQ pair production as a function of VLQ mass for the $ {\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{H})} = $ 100% branching fraction hypothesis. The solid black line indicates the observed limit and the dashed line indicates the expected limit with 1 sigma (green band) and 2 sigma (yellow band) uncertainties. The theoretical cross section and its uncertainty are shown as the red line and pale red band; the band is only slightly visible outside the line. |
png pdf |
Figure 11-b:
The 95% confidence limit on the cross section for VLQ pair production as a function of VLQ mass for the $ {\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{Z})} = $ 100% branching fraction hypothesis. The solid black line indicates the observed limit and the dashed line indicates the expected limit with 1 sigma (green band) and 2 sigma (yellow band) uncertainties. The theoretical cross section and its uncertainty are shown as the red line and pale red band; the band is only slightly visible outside the line. |
png pdf |
Figure 11-c:
The 95% confidence limit on the cross section for VLQ pair production as a function of VLQ mass for the $ {\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{H})} = {\mathcal {B}(\mathrm{B} \to \mathrm{b} \mathrm{Z})} = $ 50% branching fraction hypothesis. The solid black line indicates the observed limit and the dashed line indicates the expected limit with 1 sigma (green band) and 2 sigma (yellow band) uncertainties. The theoretical cross section and its uncertainty are shown as the red line and pale red band; the band is only slightly visible outside the line. |
| Tables | |
png pdf |
Table 1:
Signal efficiencies of the offline ${H_{\mathrm {T}}}$ selection, in%, for each of the jet multiplicity channels, for three VLQ masses (1000, 1200, and 1400 GeV). The efficiency is the fraction of events in each jet multiplicity category satisfying the $ {H_{\mathrm {T}}} > $ 1350 GeV selection. Statistical uncertainties are negligible and therefore omitted. |
png pdf |
Table 2:
Summary of the minimum number of single and double $\mathrm{b}$ tags required for each jet multiplicity and event mode. |
png pdf |
Table 3:
Values of the BJTF for data events with ${m_\text {VLQ}}$ in the range 500-800 GeV for each of the three event modes and three jet multiplicities. |
png pdf |
Table 4:
Systematic uncertainties common to all three event modes and all three jet multiplicities. All uncertainties listed here are rate uncertainties, meaning they affect only the normalization. |
png pdf |
Table 5:
Systematic uncertainties for each event mode and jet multiplicity. The reported values indicate the uncertainty in the event yield in a $\pm $75 GeV window about the signal peak for a generated signal mass $m_{\mathrm{B}} = $ 1600 GeV. |
png pdf |
Table 6:
Optimized values of the ${\chi ^2_\text {mod}/\text {ndf}}$ selection as a function of jet multiplicity and event mode. |
| Summary |
| This paper describes a search for bottom-type, vector-like quark (VLQ) pair production in data collected by the CMS detector in 2016-2018 at $\sqrt{s} = $ 13 TeV, where the VLQ B decays into a $\mathrm{b}$ or $\mathrm{\bar{b}}$ quark and either a Higgs boson H or a Z boson. The analysis targets the fully hadronic ${\mathrm{B} \to \mathrm{b}\mathrm{H}}$ and ${\mathrm{B} \to \mathrm{b}\mathrm{Z}}$ decays by tagging jets and using a modified ${\chi^2}$ metric to reconstruct the event. Different jet multiplicity categories were used to account for the fact that Higgs or Z boson decays can produce either two distinct jets or, if highly Lorentz boosted, a single merged jet. Backgrounds were estimated from a region of low VLQ mass and extrapolated into the signal region using a modified ${\chi^2}$ control region. Limits were set on the VLQ mass at 95% confidence level as a function of the branching fractions for ${\mathrm{B} \to \mathrm{b}\mathrm{H}}$ and ${\mathrm{B} \to \mathrm{b}\mathrm{Z}}$. Compared to previous measurements [18,17], limits on the B VLQ mass have been increased from 1010 to 1570 GeV in the ${\mathcal{B}(\mathrm{B} \to \mathrm{b}\mathrm{H})} = $ 100% case, from 1070 to 1390 GeV in the ${\mathcal{B}(\mathrm{B} \to \mathrm{b}\mathrm{Z})} = $ 100% case, and from 1025 to 1450 GeV in the ${\mathcal{B}(\mathrm{B} \to \mathrm{b}\mathrm{H})} = {\mathcal{B}(\mathrm{B} \to \mathrm{b}\mathrm{Z})} = $ 50% case. |
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