Search for Higgs boson production in oppositely charged dilepton and missing energy events in $p\overline{p}$ collisions at $\sqrt{s}\mathbf{=}1.96\mathrm{TeV}$

We present a search for the standard model Higgs boson using events with two oppositely charged leptons and large missing transverse energy as expected in $H\to WW$ decays. The events are selected from data corresponding to $8.6{\mathrm{fb}}^{-1}$ of integrated luminosity in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ collected with the D0 detector at the Fermilab Tevatron Collider. No significant excess above the standard model background expectation in the Higgs boson mass range this search is sensitive to is observed, and upper limits on the Higgs boson production cross section are derived.

Figure 1

(a) The dilepton invariant mass, (b) ${\mathrm{E̸}}_T$, (c) $\Delta \varphi$ between the leptons, and (d) minimum transverse mass for the $e\mu$ channel at the preselection stage. The last bin also includes all events above the upper range of the histogram (a),(b),(d). The signal distribution shown corresponds to a Higgs boson mass of 165 GeV. The hatched bands show the total systematic uncertainty on the background prediction.

Figure 2

(a) The dilepton mass, (b) ${\mathrm{E̸}}_T$, (c) $\Delta \varphi$ between the leptons, and (d) minimum transverse mass for the $ee$ channel at the preselection stage. The last bin also includes all events above the upper range of the histogram (a),(b),(d). The signal distribution shown corresponds to a Higgs boson mass of 165 GeV. The hatched bands show the total systematic uncertainty on the background prediction.

Figure 3

(a) The dilepton mass, (b) ${\mathrm{E̸}}_T$, (c) $\Delta \varphi$ between the leptons, and (d) minimum transverse mass for the $\mu \mu$ channel at the preselection stage. The last bin also includes all events above the upper range of the histogram (a),(b),(d). The signal distribution shown corresponds to a Higgs boson mass of 165 GeV. The hatched bands show the total systematic uncertainty on the background prediction.

Figure 4

$M_T^{\min }$ distribution for the $e\mu$ channel in the (a) 0-jet bin, (b) 1-jet bin, and (c) $\ge 2$-jet bin. $M_{T2}$ distribution for the $e\mu$ channel in the (d) 0-jet bin, (e) 1-jet bin, and (f) $\ge 2$-jet bin. The last bin also includes all events above the upper range of the histogram. The signal distribution shown corresponds to a Higgs boson mass of 165 GeV. The hatched bands show the total systematic uncertainty on the background prediction.

Figure 5

DY-BDT discriminant for the 0-jet (top row), 1-jet (middle row), and $\ge 2$-jet (bottom row) for the $ee$ [left (a),(c),(e)] and $\mu \mu$ [right (b),(d),(f)] final states. The discriminant shown is trained for a Higgs boson mass of 165 GeV. A final selection requirement is applied in the above distributions of 0.35, $-0.6$, and $-0.85$ for the $ee$ final state and 0.9, 0, and $-0.7$ for the $\mu \mu$ final state, in the 0-jet, 1-jet, and $\ge 2$-jet bins, respectively. The hatched bands show the total systematic uncertainty on the background prediction.

Figure 6

The (left column) $\Delta \varphi ({\ell }_1,{\ell }_2)$ and (right column) $\Delta R({\ell }_1,{\ell }_2)$ for the $e\mu$ (a),(b), $ee$ (c),(d), and $\mu \mu$ (e),(f) channel at the final selection stage. The signal distribution shown corresponds to a Higgs boson mass of 165 GeV. The hatched bands show the total systematic uncertainty on the background prediction.

Figure 7

The ${\mathrm{E̸}}_T^{\mathrm{special}}$ for the $ee$ (a) and $\mu \mu$ (b) channel at the final selection stage. The last bin includes all events above the upper range of the histogram. The signal distribution shown corresponds to a Higgs boson mass of 165 GeV. The last bin also includes all events above the upper range of the histogram. The hatched bands show the total systematic uncertainty on the background prediction.

Figure 8

The quality variable for (a) the $ee$ channel and (b) the $\mu \mu$ channel at the final selection stage. The signal distribution shown corresponds to a Higgs boson mass of 165 GeV. The hatched bands show the total systematic uncertainty on the background prediction.

Figure 9

The (a) smallest $b$-tagging MVA output and (b) largest $b$-tagging MVA output for the $\ge 2$-jet multiplicity bin, for all channels summed up at the final selection stage. The signal distribution shown corresponds to a Higgs boson mass of 165 GeV. The hatched bands show the total systematic uncertainty on the background prediction.

Figure 10

Final BDT discriminant for the (top row) 0-jet, (middle row) 1-jet, and (bottom row) $\ge 2$-jet bins for the $e\mu$ final state for Higgs boson masses of 125 GeV [left (a),(c),(e)] and 165 GeV [right (b),(d),(f)]. The hatched bands show the total systematic uncertainty on the background prediction.

Figure 11

Final BDT discriminant for the (top row) 0-jet, (middle row) 1-jet, and (bottom row) $\ge 2$-jet bins for the $ee$ final state for Higgs boson masses of 125 GeV [left (a),(c),(e)] and 165 GeV [right (b),(d),(f)]. The hatched bands show the total systematic uncertainty on the background prediction.

Figure 12

Final BDT discriminant for the (top row) 0-jet, (middle row) 1-jet, and (bottom row) $\ge 2$-jet bins for the $\mu \mu$ final state for Higgs boson masses of 125 GeV [left (a),(c),(e)] and 165 GeV [right (b),(d),(f)]. The hatched bands show the total systematic uncertainty on the background prediction.

Figure 13

The background-subtracted data distribution for the final discriminant, summed in bins with similar signal to background ratio, for the $WW$ cross section measurement. The uncertainties shown on the background-subtracted data points are the square roots of the postfit background predictions in each bin, representing the expected statistical uncertainty on the data. Also shown is the $\pm 1$ s.d. band on the total background after fitting.

Figure 14

The background-subtracted data distributions for the final discriminants, summed in bins with similar signal to background ratio, for (a) $M_H=125\mathrm{GeV}$ and (b) $M_H=165\mathrm{GeV}$. The uncertainties shown on the background-subtracted data points are the square roots of the postfit background predictions in each bin, representing the expected statistical uncertainty on the data. Also shown is the $\pm 1$ s.d. band on the total background after fitting.

Figure 15

Excluded cross section, $\sigma (p\overline{p}\to H+X)$, at the 95% C.L. in units of the SM cross section as a function of $M_H$ using (a) all channels, (b) $e\mu$ channel, (c) $ee$ channel, (d) $\mu \mu$ channel.

Figure 16

The observed LLR (solid line) as a function of $M_H$ using (a) all channels, (b) $e\mu$ channel, (c) $ee$ channel, (d) $\mu \mu$ channel. Also shown are the expected LLR distributions for the background-only hypothesis (dashed line) and for the $\mathrm{\text{signal}}+\mathrm{\text{background}}$ (dash-dotted line) hypothesis, with the dark grey and light grey bands indicating $\pm 1$ and $\pm 2$ s.d. fluctuations of the expected LLR distributions for the background-only hypothesis, respectively.