Study of associated Higgs boson (WH) Production in the three leptons final state at 7 TeV

Abstract

We report a search for the associated Higgs production in the 3 leptons final state in pp collisions at sqrt(s) = 7 TeV. The analysis is performed using the LHC data recorded with the CMS detector, corresponding to an integrated luminosity of 4.6 fb⁻¹. Candidates are selected in events with three leptons, electrons or muons, large missing energy and low hadronic activity. No significant excess of events above the standard model background expectation is observed. The observed (expected) upper limits at the 95% confidence level are 10.4 (12.1) times larger than the standard model Higgs expectation for mH = 120 GeV.

Main Results

A search has been made for Higgs bosons with WH (→ W⁺W^-) → 3l 3ν in the pp collision 2011 data at sqrt(s) = 7 TeV with the CMS detector. A cut and count mass independent event selection is performed. The observed number of data events and expected number of signal and background events at different stages of the cut flow are shown in the Table below.

* Yields at different stages of the analysis:

stage	WH(→ ττ) 120	WH(→ WW) 120	data	all bkg.	WZ → 3lν	ZZ → 4l	top + Z/γ*	W/Z + γ
3-lepton preselection	2.1 ± 0.0	3.5 ± 0.1	950	968.3 ± 11.9	482.9 ± 1.8	78.4 ± 0.9	348.0 ± 9.7	58.9 ± 6.7
min-MET > 40 GeV	1.0 ± 0.0	1.8 ± 0.1	244	270.5 ± 4.4	208.2 ± 1.1	7.9 ± 0.3	54.5 ± 4.3	0.0 ± 0.0
Z removal	0.4 ± 0.0	1.0 ± 0.1	40	47.9 ± 3.1	15.9 ± 0.4	0.7 ± 0.1	31.3 ± 3.1	0.0 ± 0.0
top veto	0.1 ± 0.0	0.6 ± 0.1	12	14.2 ± 1.3	8.8 ± 0.4	0.4 ± 0.1	4.9 ± 1.3	0.0 ± 0.0
Δ R(ll) and mll	0.1 ± 0.0	0.5 ± 0.1	7	8.5 ± 0.9	5.7 ± 0.2	0.3 ± 0.1	2.6 ± 0.9	0.0 ± 0.0

No significant excess of events is observed with respect to the background prediction and calculated upper limits with 4.6 fb⁻¹ of data are shown in Figure 1. The observed (expected) upper limits at the 95% confidence level are 10.4 (12.1) times larger than the SM Higgs expectation for mH = 120 GeV. The fermiophobic Higgs hypothesis is also considered, in which the Higgs boson is produced either via the vector boson fusion process or the associated production with a W or Z boson. The 95% C.L. upper limit in the presence of a fermiophobic Higgs boson is shown in Figure 2.

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Figure 1: Upper Limits at 95% C.L. in the standard model Higgs scenario

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Figure 2: Upper Limits at 95% C.L. in the Fermiophobic Higgs Scenario

Kinematic distributions

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Dilepton mass difference with respect to mZ after all other requirements except the Z veto.

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Smallest ΔR between the opposite charged lepton pairs after all other requirements except the ΔR cut.

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min-MET distribution after the trilepton preselection.

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Leading jet pT after the z veto (3 lepton preselection + min-MET + Zremoval conditions).

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pT of leading lepton after all selection requirements are applied. The last bin also contains the overflow events.

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pT of subleading lepton after all selection requirements are applied.

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pT of trailing lepton after all selection requirements are applied.