Search for the Associated Production of the Standard-Model Higgs Boson in the All-Hadronic Channel

We report on a search for the standard-model Higgs boson in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ using an integrated luminosity of $2.0{\mathrm{fb}}^{-1}$. We look for production of the Higgs boson decaying to a pair of bottom quarks in association with a vector boson $V$ ($W$ or $Z$) decaying to quarks, resulting in a four-jet final state. Two of the jets are required to have secondary vertices consistent with $B$-hadron decays. We set the first 95% confidence level upper limit on the $VH$ production cross section with $V(\to q\overline{q}/q{q}^{\prime })H(\to b\overline{b})$ decay for Higgs boson masses of $100–150\mathrm{GeV}/c^2$ using data from run II at the Fermilab Tevatron. For $m_H=120\mathrm{GeV}/c^2$, we exclude cross sections larger than 38 times the standard-model prediction.

Figure 1

Regions in the plane of $m_{bb}$, invariant mass of the two $b$-jets, and $m_{qq}$, invariant mass of the two other jets. The tag and tune regions are used to define and tune the tag rate function used to predict the background contribution from $b\overline{b}$ production in the signal region. The control region is used to estimate a systematic uncertainty on the interpolation of the tag rate function into the signal region.

Figure 2

Systematic uncertainties on the number of events expected for the multijet background model as a function of the discriminant $Q$, from three sources described in the text. Relative uncertainties are shown in the lower pane.

Figure 3

Predicted and observed distribution of the $Q$ discriminant in the signal region (see Fig. 1) in $2.0{\mathrm{fb}}^{-1}$ of integrated luminosity. Lower pane shows data with the dominant QCD contribution subtracted.