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Search for charged Higgs boson in ttbar in pp collisions at $\sqrt{s}=7$TeV

Main Results

The large top quark production cross section at the Large Hadron Collider offers the opportunity to search for the charged Higgs boson as the decay $t\rightarrow H^+b\rightarrow \tau^+\nu b$ can be large in extensions of the standard model, if the mass is lighter than the top quark mass. A direct search for the charged Higgs boson in events with one lepton (electron or muon), at least two jets, missing transverse energy, and one hadronically decaying tau lepton has been performed in 36 pb$^{-1}$ of data collected in proton-proton collisions at $\sqrt{s}=7$ TeV. We do not find a signal in our search and derive an upper limit on the branching ratio $BR(t\rightarrow H^+b)\simeq 0.25-0.28$ for masses between 80 and 140GeV/$c^2$, when assuming $BR(H^+\rightarrow \tau^+\nu)=1$.

Figures and Tables from CMS-HIG-11-002

FigureSorted descending Label Description
Table 2 Number of expected events for the backgrounds, signal events from $t \bar{t} \rightarrow H^{\pm}bH^{\mp}\bar{b}$ (HH) and $t \bar{t} \rightarrow W^{\pm}bH^{\mp}\bar{b}$ (WH) processes at $M_{H ^{\pm}}$=120 GeV/$c^2$, and the number of observed events after the final event selection. Statistical and systematic uncertainties are shown. The statistical uncertainties are due to MC statistics, while for the $\tau$-fakes the statistical uncertainties are due to the fake rate in the data. Of the 40 events found in the data, 16~(24) events are in the $e\tau$ ($\mu\tau$) final state, which is expected as the electron efficiency is lower than the muon efficiency.
Table 1 The systematics uncertainties for backgrounds, signal events from $t \bar{t} \rightarrow H^{\pm}bH^{\mp}\bar{b}$ (HH) and $t \bar{t} \rightarrow W^{\pm}bH^{\mp}\bar{b}$ (WH) processes at $M_{H ^{\pm}}$=120 GeV/%$c^2$. These systematic uncertainties are given as the input for the exclusion limit calculation.
Figure 4, left Inclusive jet $p_T$ distribution for $\ell+\geq3$ jet events after the MET cut, and with at least two jets with $p_T>$ 30 GeV/c and at least one jet with $p_T>$20 GeV/c. Entries in the last bin include the overflows.
Figure 7 Upper limit on $BR(t\rightarrow H^{+}b)$ assuming $BR(H^{+} \rightarrow \tau \nu)=1$ as a function of $M_{H^{+}}$. The yellow band shows the $\pm 1\sigma$ band around the expected limit.
Figure 2, right MET distribution for events with one isolated lepton and at least two jets; the hatched area shows the uncertainty. The last bin includes the events in the overflow bins.
Figure 2, left Jet multiplicity distribution ($p_T>30$ GeV/c, $\eta<2.4$) after requiring one isolated lepton.
Figure 3 Data and MC event yields at various levels of the selection.
Figure 4, right Probability that a jet fakes a $\tau$-jet as obtained from the QCD multi-jet events taken during runs with and without pileup.
Figure 1, left Feynmann diagram of $t\bar t$ production in the SM "tau dilepton" final state.
Figure 1, right Feynmann diagram of $t\bar t$ production in the presence of MSSM charged Higgs boson.
Figure 5 Expected number of $t \bar{t}$ events after the final event selection as a function of the branching ratio $BR(t\rightarrow  H^{+}b)$ for $M_{H ^{+}}$=120 GeV/$c^2$. Expectations are also shown separately for WH, HH and $t \bar{t} \rightarrow W^+bW^-\bar{b}$ (WW) contributions.
Figure 6 The relation between $N_{up}$ and the upper limit on $BR(t\rightarrow  H^{+}b)$ for the observed and the expected limit with $\pm 1\sigma$ error band shown in yellow color for $M_{H^{\pm}}$=120~GeV/c$^2$, where $BR(H^{+} \rightarrow \tau \nu)=1$ is assumed.

-- MicheleGallinaro - 14-Mar-2011

Topic attachments
I Attachment History Action Size Date Who Comment
PNGpng EventDist_brLimit_hps0_os.png r1 manage 19.0 K 2011-03-14 - 17:29 MicheleGallinaro  
PNGpng EventDist_hpsLoose.png r1 manage 19.3 K 2011-03-14 - 17:28 MicheleGallinaro  
PNGpng Table1.png r1 manage 55.1 K 2011-03-14 - 18:09 MicheleGallinaro  
PNGpng Table2.png r1 manage 114.9 K 2011-03-14 - 18:11 MicheleGallinaro  
PNGpng feyn_wh_LHC.png r1 manage 8.3 K 2011-03-15 - 16:30 MicheleGallinaro  
PNGpng feyn_ww_LHC.png r1 manage 8.6 K 2011-03-15 - 16:29 MicheleGallinaro  
PNGpng hps0_yields.png r1 manage 14.2 K 2011-03-14 - 17:17 MicheleGallinaro  
PNGpng hps_Loose_eff_vs_Pt_diff_data.png r1 manage 11.8 K 2011-03-14 - 17:26 MicheleGallinaro  
PNGpng leptonjets_pf_jetmultiplicity_init_noratio.png r1 manage 13.5 K 2011-03-14 - 17:08 MicheleGallinaro  
PNGpng leptonjets_pf_met_2j_syst.png r1 manage 20.8 K 2011-03-14 - 17:16 MicheleGallinaro  
PNGpng limit_hps_loose_upto140GeV.png r1 manage 16.0 K 2011-03-14 - 17:43 MicheleGallinaro  
PNGpng pf_wplusjets_pt.png r1 manage 19.5 K 2011-03-14 - 17:18 MicheleGallinaro  
Unknown file formattex summary-tab-tau-3-syst.tex r1 manage 1.1 K 2011-03-14 - 17:46 MicheleGallinaro  
Unknown file formattex summary-tab-tau-3.tex r1 manage 0.9 K 2011-03-14 - 17:27 MicheleGallinaro  
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Topic revision: r2 - 2011-03-15 - MicheleGallinaro
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