Search for the Standard Model Higgs Boson in the Missing Energy and Acoplanar $b$-Jet Topology at $\sqrt{s}=1.96\mathrm{TeV}$

We report a search for the standard model Higgs boson in the missing energy and acoplanar $b$-jet topology, using an integrated luminosity of $0.93{\mathrm{fb}}^{-1}$ recorded by the D0 detector at the Fermilab Tevatron $p\overline{p}$ Collider. The analysis includes signal contributions from $p\overline{p}\to ZH\to \nu \overline{\nu }b\overline{b}$, as well as from $WH$ production in which the charged lepton from the $W$ boson decay is undetected. Neural networks are used to separate signal from background. In the absence of a signal, we set limits on $\sigma (p\overline{p}\to VH)\times B(H\to b\overline{b})$ at the 95% C.L. of 2.6–2.3 pb, for Higgs boson masses in the range 105–135 GeV, where $V=W$, $Z$. The corresponding expected limits range from 2.8 to 2.0 pb.

Figure 1

$\mathcal{A}({\mathrm{E̸}}_T,{\mathrm{H̸}}_T)$ for data, MC physics background and instrumental background in the signal region, before implementing $b$ tagging. The final selection corresponds to $-0.1<\mathcal{A}({\mathrm{E̸}}_T,{\mathrm{H̸}}_T)<0.2$.

Figure 2

Invariant mass distribution of the two leading jets before $b$ tagging requirements.

Figure 3

NN output distributions for $M_H=115\mathrm{GeV}$ after $b$ tagging. The MC expectation for the Higgs signal is scaled up by a factor of 50.

Figure 4

95% C.L. upper limit on $\sigma (p\overline{p}\to VH)\times B(H\to b\overline{b})$ (and corresponding expected limit) for $VH$ production versus Higgs boson mass.