Search for the standard model Higgs boson in the decay channel H to ZZ to 4 leptons in pp collisions at sqrt(s) = 7 TeV

Abstract

A search for a Higgs boson in the four-lepton decay channel H to ZZ, with each Z boson decaying to an electron or muon pair, is reported. The search covers Higgs boson mass hypotheses in the range 110 < mH < 600 GeV. The analysis uses data corresponding to an integrated luminosity of 4.7 inverse femtobarns recorded by the CMS detector in pp collisions at sqrt(s) = 7 TeV from the LHC. Seventy-two events are observed with four-lepton invariant mass m[4 leptons] > 100 GeV (with thirteen below 160 GeV), while 67.1 +/- 6.0 (9.5 +/-1.3) events are expected from background. The four-lepton mass distribution is consistent with the expectation of standard model background production of ZZ pairs. Upper limits at 95% confidence level exclude the standard model Higgs boson in the ranges 134-158 GeV, 180-305 GeV, and 340 -465 GeV. Small excesses of events are observed around masses of 119, 126, and 320 GeV, making the observed limits weaker than expected in the absence of a signal.

Figures (2)

• Figure 1: a) Distribution of the four-lepton reconstructed mass for the sum of the $4\mathrm{e}$, $4{\mu}$, and $2\mathrm{e}2{\mu}$ channels. b) Expansion of the low mass range with existing exclusion limits at 95% CL; also shown are the central values and individual candidate mass measurement uncertainties. Points represent the data, shaded histograms represent the background and unshaded histogram the signal expectations.
• Figure 2: a) The significance of the local excesses with respect to the standard model expectation as a function of the Higgs boson mass, without (blue) or with (red) individual candidate mass measurement uncertainties. b) The observed and the median expected upper limits at 95% CL on $\sigma (\mathrm{p}\mathrm{p} \rightarrow {H}\xspace + X) \times \mathcal{B}({Z}{Z} \rightarrow 4\ell)$, normalized to the standard model cross section values $\sigma_\text{SM}$, for a Higgs boson in the mass range 110--600$\,\text{Ge\spaceV}\xspace$, using the CL$_\mathrm{s}$ approach. The insets expand the low mass range.