CMS-HIG-11-019

CMS-HIG-11-019 ; CERN-PH-EP-2012-123
Search for a light charged Higgs boson in top quark decays in pp collisions at $\sqrt{s}$ = 7 TeV
CMS Collaboration
25 May 2012
J. High Energy Phys. 07 (2012) 143
Abstract: Results are presented on a search for a light charged Higgs boson that can be produced in the decay of the top quark to charged H and b quark and which, in turn, decays into tau and tau neutrino. The analysed data correspond to an integrated luminosity of about 2 inverse femtobarns recorded in proton-proton collisions at sqrt(s) = 7 TeV by the CMS experiment at the LHC. The search is sensitive to the decays of the top quark pairs t anti-t to charged Higgs W b anti-b and t anti-t to charged Higgs b anti-b. Various final states have been studied separately, all requiring presence of a tau lepton from charged Higgs decays, missing transverse energy, and multiple jets. Upper limits on the branching fraction B(t to charged Higgs b) in the range of 2-3% are established for charged Higgs boson masses between 80 and 160 GeV, under the assumption that B(charged Higgs to tau anti-tau) = 1.
Links: e-print arXiv:1205.5736 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; Public twiki page ; CADI line (restricted) ;

Figures & Tables	CMS Publications

Figures
png pdf	Figure 1-a: Representative diagrams for the ${\tau }_\mathrm {h}$ +jets (a), ${\mathrm {e}}( {{\mu }}) {\tau }_\mathrm {h}$ (b), and ${\mathrm {e}} {{\mu }}$ (c) final states.
png pdf	Figure 1-b: Representative diagrams for the ${\tau }_\mathrm {h}$ +jets (a), ${\mathrm {e}}( {{\mu }}) {\tau }_\mathrm {h}$ (b), and ${\mathrm {e}} {{\mu }}$ (c) final states.
png pdf	Figure 1-c: Representative diagrams for the ${\tau }_\mathrm {h}$ +jets (a), ${\mathrm {e}}( {{\mu }}) {\tau }_\mathrm {h}$ (b), and ${\mathrm {e}} {{\mu }}$ (c) final states.
png	Figure 1:
png pdf	Figure 2: The event yield after each selection step for the ${\tau }_\mathrm {h}$ +jets analysis. The expected event yield in the presence of the ${\mathrm {t}}\rightarrow {\mathrm {H}} ^{+} {\mathrm {b}}$ , ${\mathrm {H}} ^{+}\rightarrow {\tau }^{+} {\nu _{\tau }}$ decays is shown as the dashed line for $m_{ {\mathrm {H}} ^{+}} =$ 120 GeV and under that assumption that $\mathcal {B}( {\mathrm {t}}\rightarrow {\mathrm {H}} ^{+} {\mathrm {b}}) =$ 0.05. The multijet and the ``EWK+ ${\mathrm {t}\overline {\mathrm {t}}}$ ${\tau }$ " backgrounds are measured from the data. The ``EWK+ ${\mathrm {t}\overline {\mathrm {t}}}$ no- ${\tau }$ " background is shown as estimated from simulation. The bottom panel shows the ratio of data over background along with the total uncertainties. Statistical and systematic uncertainties are added in quadrature.
png pdf	Figure 3: The transverse mass of ${\tau }_\mathrm {h}$ and ${E_{\mathrm {T}}^{\text {miss}}}$ after full event selection for the ${\tau }_\mathrm {h}$ +jets analysis. The expected event yield in the presence of the ${\mathrm {t}}\rightarrow {\mathrm {H}} ^{+} {\mathrm {b}}$ , ${\mathrm {H}} ^{+}\rightarrow {\tau }^{+} {\nu }$ decays is shown as the dashed line for $m_{ {\mathrm {H}} ^{+}} =$ 120 GeV and under the assumption that $\mathcal {B}( {\mathrm {t}}\rightarrow {\mathrm {H}} ^{+} {\mathrm {b}}) =$ 0.05. The bottom panel shows the ratio of data over background along with the total uncertainties. The ratio is not shown for ${m_\mathrm {T}}>$ 160 GeV, where the expected total number of the background events is 2.5 $\pm$ 0.3 while 5 events are observed. Statistical and systematic uncertainties are always added in quadrature.
png pdf	Figure 4-a: The event yields after each selection step for the ${\mathrm {e}} {\tau }_\mathrm {h}$ (a) and ${{\mu }} {\tau }_\mathrm {h}$ (b) analyses. The backgrounds are estimated from simulation and normalized to the standard model prediction. The expected event yield in the presence of the ${\mathrm {t}}\rightarrow {\mathrm {H}} ^{+} {\mathrm {b}}$ , ${\mathrm {H}} ^{+}$ $\rightarrow {\tau }^{+} {\nu _{\tau }}$ decays is shown as a dashed line for $m_{ {\mathrm {H}} ^{+}} =$ 120 GeV and under the assumption that $\mathcal {B}( {\mathrm {t}}\rightarrow {\mathrm {H}} ^{+} {\mathrm {b}}) =$ 0.05. The bottom panel shows the ratios of data over background with the total uncertainties. OS indicates the requirement to have opposite electric charges for a ${\tau }_\mathrm {h}$ and a ${\mathrm {e}}$ or ${{\mu }}$ . Statistical and systematic uncertainties are added in quadrature.
png pdf	Figure 4-b: The event yields after each selection step for the ${\mathrm {e}} {\tau }_\mathrm {h}$ (a) and ${{\mu }} {\tau }_\mathrm {h}$ (b) analyses. The backgrounds are estimated from simulation and normalized to the standard model prediction. The expected event yield in the presence of the ${\mathrm {t}}\rightarrow {\mathrm {H}} ^{+} {\mathrm {b}}$ , ${\mathrm {H}} ^{+}$ $\rightarrow {\tau }^{+} {\nu _{\tau }}$ decays is shown as a dashed line for $m_{ {\mathrm {H}} ^{+}} =$ 120 GeV and under the assumption that $\mathcal {B}( {\mathrm {t}}\rightarrow {\mathrm {H}} ^{+} {\mathrm {b}}) =$ 0.05. The bottom panel shows the ratios of data over background with the total uncertainties. OS indicates the requirement to have opposite electric charges for a ${\tau }_\mathrm {h}$ and a ${\mathrm {e}}$ or ${{\mu }}$ . Statistical and systematic uncertainties are added in quadrature.
png	Figure 4:
png pdf	Figure 5: The event yield after each selection step for the ${\mathrm {e}} {{\mu }}$ analysis. The backgrounds are from simulation and normalized to the standard model prediction. The expected event yield in the presence of the ${\mathrm {t}}\rightarrow {\mathrm {H}} ^{+} {\mathrm {b}}$ , ${\mathrm {H}} ^{+}\rightarrow {\tau }^{+} {\nu _{\tau }}$ decays is shown as a dashed line for $m_{ {\mathrm {H}} ^{+}}=$ 120 GeV under the assumption that $\mathcal {B}( {\mathrm {t}}\rightarrow {\mathrm {H}} ^{+} {\mathrm {b}}) =$ 0.05. The bottom panel shows the ratios of data over background with the total uncertainties. The requirement for the ${\mathrm {e}}$ and ${{\mu }}$ to have opposite electric charges is labelled as OS. Statistical and systematic uncertainties are added in quadrature.
png pdf	Figure 6-a: The expected number of ${\mathrm {t}\overline {\mathrm {t}}}$ events after event selection for the ${{\mu }} {\tau }_\mathrm {h}$ (a) and ${\mathrm {e}} {{\mu }}$ (b) final states as a function of the branching fraction $\mathcal {B}( {\mathrm {t}}\rightarrow {\mathrm {H}} ^{+} {\mathrm {b}})$ for $m_{ {\mathrm {H}} ^{+}} =$ 120 GeV. Expectations are shown separately for the ${\mathrm {W}} {\mathrm {H}}$ , ${\mathrm {H}} {\mathrm {H}}$ , and ${\mathrm {W}} {\mathrm {W}}$ contributions.
png pdf	Figure 6-b: The expected number of ${\mathrm {t}\overline {\mathrm {t}}}$ events after event selection for the ${{\mu }} {\tau }_\mathrm {h}$ (a) and ${\mathrm {e}} {{\mu }}$ (b) final states as a function of the branching fraction $\mathcal {B}( {\mathrm {t}}\rightarrow {\mathrm {H}} ^{+} {\mathrm {b}})$ for $m_{ {\mathrm {H}} ^{+}} =$ 120 GeV. Expectations are shown separately for the ${\mathrm {W}} {\mathrm {H}}$ , ${\mathrm {H}} {\mathrm {H}}$ , and ${\mathrm {W}} {\mathrm {W}}$ contributions.
png	Figure 6:
png pdf	Figure 7-a: Upper limit on $\mathcal {B}( {\mathrm {t}}\rightarrow {\mathrm {H}} ^{+} {\mathrm {b}})$ as a function of $m_{ {\mathrm {H}} ^{+}}$ for the fully hadronic (a) and the e ${\tau }_\mathrm {h}$ (b) final states. The $\pm 1 \sigma$ and $\pm 2 \sigma$ bands around the expected limit are also shown.
png pdf	Figure 7-b: Upper limit on $\mathcal {B}( {\mathrm {t}}\rightarrow {\mathrm {H}} ^{+} {\mathrm {b}})$ as a function of $m_{ {\mathrm {H}} ^{+}}$ for the fully hadronic (a) and the e ${\tau }_\mathrm {h}$ (b) final states. The $\pm 1 \sigma$ and $\pm 2 \sigma$ bands around the expected limit are also shown.
png	Figure 7:
png pdf	Figure 8-a: Upper limit on $\mathcal {B}( {\mathrm {t}}\rightarrow {\mathrm {H}} ^{+} {\mathrm {b}})$ as a function of $m_{ {\mathrm {H}} ^{+}}$ for the ${{\mu }} {\tau }_\mathrm {h}$ (a) and ${\mathrm {e}} {{\mu }}$ (b) final states. The $\pm 1 \sigma$ and $\pm 2 \sigma$ bands around the expected limit are also shown.
png pdf	Figure 8-b: Upper limit on $\mathcal {B}( {\mathrm {t}}\rightarrow {\mathrm {H}} ^{+} {\mathrm {b}})$ as a function of $m_{ {\mathrm {H}} ^{+}}$ for the ${{\mu }} {\tau }_\mathrm {h}$ (a) and ${\mathrm {e}} {{\mu }}$ (b) final states. The $\pm 1 \sigma$ and $\pm 2 \sigma$ bands around the expected limit are also shown.
png	Figure 8:
png pdf	Figure 9-a: a: the upper limit on $\mathcal {B}( {\mathrm {t}}\rightarrow {\mathrm {H}} ^{+} {\mathrm {b}})$ as a function of $m_{ {\mathrm {H}} ^{+}}$ obtained from the combination of the all final states. b: the exclusion region in the MSSM $M_{ {\mathrm {H}} ^{+}}$ - $\tan\beta$ parameter space obtained from the combined analysis for the MSSM $m_\mathrm {h}^\text {max}$ scenario. The $\pm 1 \sigma$ and $\pm 2 \sigma$ bands around the expected limit are also shown.
png pdf	Figure 9-b: a: the upper limit on $\mathcal {B}( {\mathrm {t}}\rightarrow {\mathrm {H}} ^{+} {\mathrm {b}})$ as a function of $m_{ {\mathrm {H}} ^{+}}$ obtained from the combination of the all final states. b: the exclusion region in the MSSM $M_{ {\mathrm {H}} ^{+}}$ - $\tan\beta$ parameter space obtained from the combined analysis for the MSSM $m_\mathrm {h}^\text {max}$ scenario. The $\pm 1 \sigma$ and $\pm 2 \sigma$ bands around the expected limit are also shown.
png	Figure 9:

Tables
png pdf	Table 1: Numbers of expected events in the ${\tau }_\mathrm {h}$ +jets analysis for the backgrounds and the Higgs boson signal from ${\mathrm {H}} {\mathrm {H}}$ and ${\mathrm {W}} {\mathrm {H}}$ processes at $m_{ {\mathrm {H}} ^{+}} =$ 120 GeV, and the number of observed events after the final event selection. Unless stated differently, the expected background events are from simulation.
png pdf	Table 2: Numbers of expected events in the ${\mathrm {e}} {\tau }_\mathrm {h}$ and $\mu {\tau }_\mathrm {h}$ analyses for the backgrounds and the Higgs boson signal from ${\mathrm {W}} {\mathrm {H}}$ and ${\mathrm {H}} {\mathrm {H}}$ processes at $m_{ {\mathrm {H}} ^{+}} =$ 120 GeV, and the number of observed events after the final event selection. Unless stated differently, the expected background events are from simulation.
png pdf	Table 3: Number of expected events in the ${\mathrm {e}} {{\mu }}$ analysis for the backgrounds, the Higgs boson signal from ${\mathrm {H}} {\mathrm {H}}$ and ${\mathrm {W}} {\mathrm {H}}$ processes at $m_{ {\mathrm {H}} ^{+}}=$ 120 GeV, and the number of observed events after all selection requirements. The expected background events are from simulation.
png pdf	Table 4: The systematic uncertainties on event yields (in percent) for the ${\tau }_\mathrm {h}$ +jets analysis for background processes and for the Higgs boson signal processes ${\mathrm {W}} {\mathrm {H}}$ and ${\mathrm {H}} {\mathrm {H}}$ in the range of $m_{ {\mathrm {H}} ^{+}} =$ 80-160 GeV. The range of errors for the signal processes is given for the Higgs boson mass range of 80-160 GeV.
png pdf	Table 5: The systematic uncertainties on event yields (in percent) for the ${{\mu }} {\tau }_\mathrm {h}$ analysis for the background processes and for the Higgs boson signal processes ${\mathrm {W}} {\mathrm {H}}$ and ${\mathrm {H}} {\mathrm {H}}$ for $m_{ {\mathrm {H}} ^{+}} =$ 120 GeV.
png pdf	Table 6: The systematic uncertainties on event yields (in percent) for the ${\mathrm {e}} {{\mu }}$ analysis for the background processes and for the Higgs boson signal processes ${\mathrm {W}} {\mathrm {H}}$ and ${\mathrm {H}} {\mathrm {H}}$ at $m_{ {\mathrm {H}} ^{+}} =$ 120 GeV.
png pdf	Table 7: The expected range and observed 95% CL upper limit for $\mathcal {B}( {\mathrm {t}}\rightarrow {\mathrm {H}} ^{+} {\mathrm {b}})$ as a function of $m_{ {\mathrm {H}} ^{+}}$ for the combination of the fully hadronic, ${\mathrm {e}} {\tau }_\mathrm {h}$ , ${{\mu }} {\tau }_\mathrm {h}$ , and ${\mathrm {e}} {{\mu }}$ final states.