-- AlexandrosAttikis - 18-Jul-2011

Search for the charged Higgs boson with H+->tau+ nu decay mode in top quark decays

This is a condensed description with plots for the analysis CMS-HIG-11-008

Abstract

The search for the light charged Higgs boson (mH+ < mt) produced from the top quark decay t ->H+b and decaying into tau+ nu has been performed using about 1 fb-1 of data collected in proton-proton collisions at sqrt(s) =7 TeV. The dominant source of top quarks at LHC is the pp -> t tbar process, therefore the charged Higgs boson has been searched for in the subsequent decay products of the top quark pairs: t tbar -> H+W-b bbar and t tbar -> H+H- b bbar . Three types of final states with large missing transverse energy and b-tagged jets have been analyzed: with electron plus muon pair, with muon plus tau decaying hadronically and with no leptons and tau decaying hadronically. Combining the results of these three analyzes and assuming BR(H+ -> tau+ nu)=1 we extract upper limits on the BR(t -> H+b) < 4-5 % depending on the Higgs boson mass fo the interval 80 < mH+ < 160 GeV/c2.

Main Results

The search for the light charged Higgs boson (mH+ < mt) produced from the top quark decay t -> H+b and decaying into tau+ nu has been performed using about 1 fb-1 of data collected in proton-proton collisions at sqrt(s)=7 TeV. The fully hadronic, lepton-tau and e-mu final state toplogies have been analysed and the upper limit 4-5 % on the BR(t -> H+b) has been obtained for the Higgs boson mass interval 80 < mH+ < 160 GeV/c2 assuming Br(H+ -> tau+ nu)=1.

Figures from CMS-HIG-11-008

Figure	Format	Description
	pdf, png, eps	The expected number of ttbar events after the event selection for mu-tau final state as a function of the branching ratio BR(t -> H+b) (assuming BR(H+ -> tau+ nu )=1) for mH+=120 GeV/c2. Expectations are shown separately for WH, HH, and ttbar -> W+bW-bbar (WW) contributions.
	pdf, png, eps	The expected number of ttbar events after the event selection for e-mu final state as a function of the branching ratio BR(t -> H+b) (assuming BR(H+ -> tau+ nu )=1) for mH+=120 GeV/c2. Expectations are shown separately for WH, HH, and ttbar -> W+bW-bbar (WW) contributions.
	pdf, png, eps	Upper limit on BR(t -> H+b) assuming BR(H+ -> tau+ nu)=1 as a function of mH+ for the fully hadronic final state. The yellow bands show the one and two sigma bands around the expected limit.
	pdf, png, eps	Upper limit on BR(t -> H+b) assuming BR(H+ -> tau+ nu)=1 as a function of mH+ for the mu-tau final state. The yellow bands show the one and two sigma bands around the expected limit.

	pdf, png, eps	Upper limit on BR(t -> H+b) assuming BR(H+ -> tau+ nu)=1 as a function of mH+ for the combination of the fully hadronic, the mu-tau and the e-mu final states. The yellow bands show the one and two sigma bands around the expected limit.
	pdf, png, eps	Upper limit on BR(t -> H+b) assuming BR(H+ -> tau+ nu)=1 as a function of mH+ for the e-mu final state. The yellow bands show the one and two sigma bands around the expected limit.
	pdf, png, eps	The exclusion region in the MSSM mH+ - tan(beta) parameter space obtained from the combined analysis for the MSSM m^max_h scenario.

Additional plots for public talks (Fully Hadronic Final State - CMS AN 2011/126)

Figure	Format	Description
	pdf, png, eps	Distribution of pT for the tau jet after t identification, excluding the t-jet isolation.
	pdf, png, eps	Distribution of PFMET after t jet identification, excluding the t jet isolation.
	pdf, png, eps	Distribution of the number of selected jets with pT > 30 GeV and eta < 2.4 after tau jet identification, lepton veto and MET cuts. Isolation is not applied for the tau jet.
	pdf, png, eps	Distribution of the number of selected b jets with pT > 30 GeV and eta < 2.4 after tau jet identification, lepton veto, MET cuts and the requirement of three hadronic jets. Isolation is not applied for the tau jet.
	pdf, png, eps	Distribution of events yields for the signal and backgrounds after every selection step. The expected event yield in the presence of the t -> bH+, H+ -> tau+ nu decays is shown as the dashed red line for mH± = 120 GeV/c2 and assuming BR(t -> bH+) = 0.2 and BR(H -> tau+ nu) = 1.
	pdf, png, eps	Signal selection efficiencies for the trigger (full triangle up), tau identification (full cross), MET cut (full square), requirement of three jets (full circle), b tagging (full triangle down) and total efficiency (full star) as a function of mH± in the tt ->bH+bW- process.
	pdf, png, eps	Distribution of the selected muon pT after all pre-selections without the isolation requirement, for control sample with mu + >= 3 jets used for EWK+tt tau background evaluation from dataand using the tau-embedding method.
	pdf, png, eps	Distribution of the selected muon pT after all pre-selections with the isolation requirement, for control sample with mu + >= 3 jets used for EWK+tt tau background evaluation from data and using the tau-embedding method.
	pdf, png, eps	Efficiency of the MET+b-tagging cut in pT bins of tau jet candidates, as measured from data.
	pdf, png, eps	MET distributions before and after tau jet isolation and normalized to unity, as measured from data.

Additional plots for public talks (mu-tau final state - CMS AN 2011/175)

Figure	Format	Description
	pdf, png, eps	Events yields for the signal and backgrounds after every selection step. The expected event yield in the presence of the t -> bH+, H+ -> tau+ nu decays is shown as the dashed line for mH± = 120 GeV/c2 and assuming BR(t -> bH+) = 0.2 and BR(H -> tau+ nu) = 1.
	pdf, png, eps	pT distribution of selected muon after the selection of one muon and 3 jets (two jets with pT > 30 GeV/c and one jet with pT > 20 GeV/c)
	pdf, png, eps	eta distribution of selected muon after the selection of one muon and 3 jets (two jets with pT > 30 GeV/c and one jet with pT > 20 GeV/c)
	pdf, png, eps	pT distribution of selected jets after the selection of one muon and 3 jets (two jets with pT > 30 GeV/c and one jet with pT > 20 GeV/c). Only the jets with pT > 30 GeV/c enter to these distribution.
	pdf, png, eps	eta distribution of selected jets after the selection of one muon and 3 jets (two jets with pT > 30 GeV/c and one jet with pT > 20 GeV/c), Only the jets with pT > 30 GeV/c enter to these distribution.
	pdf, png, eps	Jet multiplicity distribution of selected jets after the selection of one muon and 3 jets (two jets with pT > 30 GeV/c and one jet with pT > 20 GeV/c), Only the jets with pT > 30 GeV/c enter to these distribution.
	pdf, png, eps	Missing transverse energy distribution after the selection of one muon and 3 jets (two jets with pT > 30 GeV/c and one jet with pT > 20 GeV/c)
	pdf, png, eps	Distribution of multiplicity of b-tagged jets after the selection of one muon, 3 jets (two jets with pT > 30 GeV/c and one jet with pT > 20 GeV/c) and Missing ET > 40 GeV
	pdf, png, eps	Distribution for pT of selected tau hadronic jet after the selection of one muon, 3 jets (two jets with pT > 30 GeV/c and one jet with pT > 20 GeV/c), Missing ET > 40 GeV and one jet tagged as b-jet
	pdf, png, eps	Distribution for eta of selected tau hadronic jet after the selection of one muon, 3 jets (two jets with pT > 30 GeV/c and one jet with pT > 20 GeV/c), Missing ET > 40 GeV and one jet tagged as b-jet
	pdf, png, eps	Distribution for tau polarization of selected 1-prong tau hadronic jet after the selection of one muon, 3 jets (two jets with pT > 30 GeV/c and one jet with pT > 20 GeV/c), Missing ET > 40 GeV and one jet tagged as b-jet
	pdf, png, eps	Distribution for pT of the jets (jets that can be mis tagged as a tau hadronic jet) after the selection of one muon, 3 jets (two jets with pT > 30 GeV/c and one jet with pT > 20 GeV/c), Missing ET > 40 GeV. It is required that one of the high pT jets ( > 30 GeV/c) is tagged as b-jet. However if there is only one b-tagged jet in an event then it does not enter to this distribution. But if there are more than one b-tagged jets present in an event, all of them are included.
	pdf, png, eps	*Distribution for the probability of a jet mis-tagged as a tau hadronic jet evaluated from QCD multijet type events. Tau jet is required to pass HPS Loose isolation and loose muon and medium electron rejection and pT > 20 GeV,	eta	< 2.4*
	pdf, png, eps	*Distribution for the probability of a jet mis-tagged as a tau hadronic jet evaluated from W+jet type events. Tau jet is required to pass HPS Loose isolation and loose muon and medium electron rejection and pT > 20 GeV,	eta	< 2.4*

Additional plots for public talks (e-mu final state - CMS AN 2011/175)

Figure	Format	Description
	pdf, png, eps	Events yields for the signal and backgrounds after every selection step. The expected event yield in the presence of the t -> bH+, H+ -> tau+ nu decays is shown as the dashed line for mH± = 120 GeV/c2 and assuming BR(t -> bH+) = 0.2 and BR(H -> tau+ nu) = 1.

Additional tables for public talks (Fully Hadronic Final State - CMS AN 2011/126)

Table	Format	Description
	pdf, png, eps	Summary of the number of events obtained from the background measurements and observed event yield. Number of events from the signal with mass point mH± = 120 GeV/c2 with BR(t -> bH+) = 0.2. Luminosity uncertainty is not included in the numbers.
	pdf, png, eps	The systematic uncertainties (in %) for the backgrounds and the signal from tt -> bH+bH- (HH) and tt -> bW+bH- (WH) processes at mH+ = 80–160 GeV/c2.

Additional tables for public talks (mu-tau Final State - CMS AN 2011/175)

Table	Format	Description
	pdf, png, eps	Summary of the number of events obtained after all selections and observed event yield. The data driven backgrounds are also included. Number of events from the signal with mass point mH± = 120 GeV/c2 with BR(t -> bH+) = 0.2. The systematic uncertainties include all relavant uncertainties including uncertainty due to luminosity
	pdf, png, eps	Systematic uncertainties for backgrounds and signal events
	pdf, png, eps	Estimated fake tau backgrounds using the data driven method

Additional tables for public talks (e-mu Final State - CMS AN 2011/175)

Table	Format	Description
	pdf, png, eps	Summary of the number of events obtained after all selections and observed event yield. Number of events from the signal with mass point mH± = 120 GeV/c2 with BR(t -> bH+) = 0.2. The systematic uncertainties include all relavant uncertainties including uncertainty due to luminosity
	pdf, png, eps	Systematic uncertainties for backgrounds and signal events

Diagrams

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