Combination of Tevatron Searches for the Standard Model Higgs Boson in the $W^{+}{W}^{-}$ Decay Mode

We combine searches by the CDF and D0 Collaborations for a Higgs boson decaying to $W^{+}{W}^{-}$. The data correspond to an integrated total luminosity of 4.8 (CDF) and 5.4 (D0) ${\mathrm{fb}}^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ at the Fermilab Tevatron collider. No excess is observed above background expectation, and resulting limits on Higgs boson production exclude a standard model Higgs boson in the mass range 162–166 GeV at the 95% C.L.

Figure 1

Background-subtracted data distributions for the discriminant histograms, summed for bins with similar $s/b$, for the $m_H=165\mathrm{GeV}$ combined search. The background has been fit to the data under the $b$-only hypothesis, and the uncertainty on the background is the post-fit systematic uncertainty. The signal, which is normalized to the SM expectation, is shown with a filled histogram. The uncertainties shown on the background-subtracted data points are the square roots of the post-fit background predictions in each bin, representing the expected statistical uncertainty on the data.

Figure 2

Distributions of LLR as functions of the Higgs boson mass. We display the median values of the LLR distribution for the $b$-only hypothesis (${\mathrm{LLR}}_b$), the $s+b$ hypothesis (${\mathrm{LLR}}_{s+b}$), and for the data (${\mathrm{LLR}}_{\mathrm{obs}}$). The shaded bands indicate the 68% and 95% probability regions in which the LLR is expected to fluctuate, in the absence of signal.

Figure 3

Observed and expected (median, for the background-only hypothesis) 95% C.L. upper limits on SM Higgs boson production. The shaded bands indicate the 68% and 95% probability regions in which $R_{\lim }$ is expected to fluctuate, in the absence of signal. The limits displayed in this figure are obtained with the Bayesian calculation.

Figure 4

Distribution of $1\mathrm{\text{−}}{\mathrm{CL}}_s$ as a function of the Higgs boson mass obtained with the ${\mathrm{CL}}_s$ method. The shaded bands indicate the 68% and 95% probability regions in which the LLR is expected to fluctuate, in the absence of signal.