Search for Doubly Charged Higgs

This is the condensed description with plots for the analysis HIG-11-007.

Abstract

A search for the doubly charged Higgs boson in pp collisions at sqrt(s) = 7 TeV is presented. The data correspond to an integrated luminosity of 0.98 fb−1 collected by the CMS experiment at the LHC. The double charged Higgs is a member of SU(2)L scalar triplet Φ in extensions of the standard model which include the seesaw mechanism of type II. The search is inclusive and is performed in events with three or more isolated charged leptons of all flavours originating from the decays of pair produced triplet components Φ++Φ−− and Φ++Φ−. No signal excess is observed and new world best lower limits at the 95% confidence level are set on the Φ±± mass, under specific assumption on the Φ++ branching fraction. If a 100% branching fraction to μμ, eμ or ee is assumed the limits are of 313 GeV in all of the cases. The limit is 266 GeV for the μτ channel and 254 GeV for the eτ channel. The limits range between 269 GeV and 297 GeV in four chosen benchmark points of the type-II see-saw model.

Main results

No significant excess is observed so new world limits are set in nine model specific assumptions of branching ratios. The limits are:

Model assumption	Combined limit on all production mechanisms	Limit on pair-production only
BR(Φ++ -> e+e+) = 100%	313 GeV	274 GeV
BR(Φ++ -> e+μ+) = 100%	313 GeV	275 GeV
BR(Φ++ -> e+τ+) = 100%	254 GeV	211 GeV
BR(Φ++ -> μ+μ+) = 100%	313 GeV	277 GeV
BR(Φ++ -> μ+τ+) = 100%	266 GeV	219 GeV
Benchmark point 1 (Normal hierarchy)	269 GeV	236 GeV
Benchmark point 2 (Inverse hierarchy)	297 GeV	263 GeV
Benchmark point 3 (Degenerate masses)	291 GeV	258 GeV
Benchmark point 4 (Equal branching ratios)	289 GeV	255 GeV

Figures from HIG-11-007

Figure	Label	Description
	Figure 1a: pdf png	Feynman diagram of associated production.
	Figure 1b: pdf png	Feynman diagram of pair production.
	Figure 2: pdf png	Cross sections of both pair and associated production processes.
	Figure 3a: pdf png	Invariant mass distribution from three lepton final state for backgrounds and data. We also show the expected contribution of a Φ++ with a mass of 150 GeV for the benchmark point BP4. The plot is after pre-selection and ∑ pT cut.
	Figure 3b: pdf png	Invariant mass distribution from three lepton final state for backgrounds and data. We also show the expected contribution of a Φ++ with a mass of 150 GeV for the benchmark point BP4. The plot is after the full selection.
	Figure 4a: pdf png	Invariant mass distribution from four lepton final state for background and data. We also show the expected contribution of a Φ++ with a mass of 150 GeV for the benchmark point BP4. The plot is after pre-selection (the expected signal yield is 24.5 events).
	Figure 4b: pdf png	Invariant mass distribution from four lepton final state for background and data. We also show the expected contribution of a Φ++ with a mass of 150 GeV for the benchmark point BP4. The plot is after the full selection (the expected signal yield is 20.7 events).
	Figure 5: pdf png	Observed Φ++ mass limits at 95% C.L. in different lepton final states. The branching ratio that are assumed in the limit calculation are indicated.
	Figure 6a: pdf png	Observed Φ++ mass limits at 95% C.L. for 100% branching fraction to ee channel.
	Figure 6b: pdf png	Observed Φ++ mass limits at 95% C.L. for 100% branching fraction to eμ channel.
	Figure 7a: pdf png	Observed Φ++ mass limits at 95% C.L. for 100% branching fraction to eτ channel.
	Figure 7b: pdf png	Observed Φ++ mass limits at 95% C.L. for 100% branching fraction to μμ channel.
	Figure 8a: pdf png	Observed Φ++ mass limits at 95% C.L. for 100% branching fraction to μτ channel.
	Figure 8b: pdf png	Observed Φ++ mass limits at 95% C.L. for 100% branching fraction to ττ channel.
	Figure 9a: pdf png	Observed Φ++ mass limits at 95% C.L. for benchmark point BP1.
	Figure 9b: pdf png	Observed Φ++ mass limits at 95% C.L. for benchmark point BP2.
	Figure 10a: pdf png	Observed Φ++ mass limits at 95% C.L. for benchmark point BP3.
	Figure 10b: pdf png	Observed Φ++ mass limits at 95% C.L. for benchmark point BP4.

Additional plots for public talks

Figure	Files	Description
	png	Observed Φ++ mass limits at 95% C.L. in different lepton final states. The branching ratio that are assumed in the limit calculation are indicated. This plot also shows the CMS results for 36 /pb
	pdf png	Invariant mass distribution from four lepton final state for background and data. We also show the expected contribution of a Φ++ with a mass of 150 GeV for the benchmark point BP4. The plot is after isolation requirement.
	pdf png	Invariant mass distribution from three lepton final state for backgrounds and data. We also show the expected contribution of a Φ++ with a mass of 150 GeV for the benchmark point BP4. The plot is after pre-selection, ∑ pT and isolation cuts.
	pdf png	Invariant mass distribution from three lepton final state for backgrounds and data. We also show the expected contribution of a Φ++ with a mass of 150 GeV for the benchmark point BP4. The plot is after pre-selection, ∑ pT, isolation and Z veto cuts.
	pdf png	Background control region for Z+jets process.
	pdf png	Background control region for QCD.