Updated search for a light charged Higgs boson in top quark decays in pp collisions at sqrt(s) = 7 TeV

This is a condensed description with plots for the analysis CMS-HIG-12-052

Abstract

Updated results are presented in the search for a light charged Higgs boson that can be produced in the top quark decay t->H+b with subsequent decay of H+ into tau+nu_tau. The search is sensitive to the decays of the top quark pairs ttbar->H+/-W-/+bbar and ttbar->H+/-HH-/+bbar. The results in the mu-tau+ET_miss+jet signature are updated with an integrated luminosity of 4.9 fb-1 recorded in proton-proton collisions at sqrt(s)=7 TeV by the CMS experiment at the LHC, and are combined with results of a previous search in other decay channels, based on an integrated luminosity of about 2 fb-1. Upper limits on the branching fraction B(t->H+b) in the range of 2-3 % are established for charged Higgs boson masses between 80 and 160 GeV, under the assumption that B(H+->tau nu) =1.

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 4.9 fb-1 of data collected in proton-proton collisions at sqrt(s)=7 TeV. The mu-tau final state topology have been analyzed and combined with previous results in the fully hadronic, e-tau, and e-mu final state. An upper limit of 2-3 % on the B(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-12-052

Figure	Label	Description
	Figure 1 png, pdf	Representative diagram for the e (mu) tau_h final state. The current analysis is performed for the muon channel, i.e. l = mu.
	Figure 2 png, pdf	The event yields after each selection step, where OS indicates the requirement to have opposite electric charges for a tau_h and a mu. The backgrounds are estimated from simulation and normalized to the standard model prediction. The expected event yield in the presence of the t->H+b, H+->tau_h nu_tau decays is shown as a dashed line for mH+ = 120 GeV and under the assumption that B(t->H+b) = 0.05. The bottom panel shows the ratios of data over background with the total uncertainties. Statistical and systematic uncertainties are added in quadrature.
	Figure 3 (left) png, pdf	Distribution of ET_miss after the full event selection. Distributions obtained from data (points) are compared with simulation. The simulated contributions are normalized to the SM predicted values. The expected event yield in the presence of the t->H+b, H+->tau_h nu_tau decays is shown as a dashed line for mH+ = 120 GeV and under the assumption that B(t->H+b) = 0.05. The last bin includes the overflow. The hatched area shows the total uncertainty.
	Figure 3 (right) png, pdf	Distribution of tau_h transverse momentum after the full event selection. Distributions obtained from data (points) are compared with simulation. The simulated contributions are normalized to the SM predicted values. The expected event yield in the presence of the t->H+b, H+->tau_h nu_tau decays is shown as a dashed line for mH+ = 120 GeV and under the assumption that B(t->H+b) = 0.05. The last bin includes the overflow. The hatched area shows the total uncertainty.
	Figure 4 png, pdf	The expected number of ttbar events after event selection as a function of the branching fraction B(t->H+b) for mH+ = 120 GeV. Expectations are shown separately for the WH, HH and WW contributions.
	Figure 5 png, pdf	Distribution of R = p_leadTrack / E_tau. Data points, total SM backgrounds and charged Higgs boson signal yields are separately normalized to unity. The "misidentified tau_h" component is estimated using the data driven method. The area shaded with lines indicates the total uncertainty.
	Figure 6 (left) png, pdf	Upper limit on B(t->H+b) as a function of mH+ for the mu-tau_h final state. The +/- 1 sigma and +/- 2 sigma bands around the expected limit are also shown.
	Figure 6 (right) png, pdf	Upper limit on B(t->H+b) as a function of mH+ for the combination of the mu-tau_h with the e-mu, e-tau_h and tau_h+jets final states from HIG-11-019. The +/- 1 sigma and +/- 2 sigma bands around the expected limit are also shown.

Tables from CMS-HIG-12-052

Table	Label	Description
	Table 1 png	Number of expected events in the mu-tau_h final state for the backgrounds and the charged Higgs boson signal from WH and HH processes at mH+ = 120 GeV, and the number of observed events after the final event selection.
	Table 2 png	The systematic uncertainties on event yields (in percent) for the background processes and for the Higgs boson signal processes WH and HH for mH+ = 120 GeV.
	Table 3 png	The expected range and observed 95% CL upper limit for B(t->H+b) as a function of mH+ for the combination of the mu-tau_h (this analysis), fully hadronic, e-tau_h and emu (from HIG-11-019) final states.

-- PietroVischia - 18-Jun-2013