Search for standard model Higgs boson production in association with a $W$ boson at CDF

We present a search for standard model Higgs boson production in association with a $W$ boson in proton-antiproton collisions ($p\overline{p}\to W^{\pm }H\to \ell \nu b\overline{b}$) at a center of mass energy of 1.96 TeV. The search employs data collected with the CDF II detector which correspond to an integrated luminosity of approximately $1{\mathrm{fb}}^{-1}$. We select events consistent with a signature of a single lepton ($e^{\pm }/{\mu }^{\pm }$), missing transverse energy, and two jets. Jets corresponding to bottom quarks are identified with a secondary vertex tagging method and a neural network filter technique. The observed number of events and the dijet mass distributions are consistent with the standard model background expectations, and we set 95% confidence level upper limits on the production cross section times branching ratio ranging from 3.9 to 1.3 pb for Higgs boson masses from 110 to $150\mathrm{GeV}/c^2$, respectively.

Figure 1

Neural network outputs obtained from trainings of $b$ vs $l$ jets (left) and $b$ vs $c$ jets (right). Output distributions for $b$, $c$, and $l$ jets are shown in solid, dashed, and dotted lines, respectively.

Figure 2

Comparisons of NN $b$-tag output in data (solid line), and Monte Carlo (dashed line) for secvtx-tagged heavy-flavor-enriched jets (left) and tagged light-flavor jets (right).

Figure 3

Number of events as a function of exclusive jet multiplicity for events with exactly one secvtx $b$-tag before (left) and after (right) applying the NN $b$-tagging requirement.

Figure 4

Number of events as a function of exclusive jet multiplicity for events with at least two secvtx $b$-tagged jets.

Figure 5

The summary of acceptance of the process $WH\to \ell \nu b\overline{b}$ in $W+2$ jet bin for various $b$-tagging strategies as a function of Higgs boson mass.

Figure 6

Comparison of significance obtained from various $b$-tagging strategies. “Tag” and “NN Tag” represent secvtx and NN $b$-tagging, respectively. The filled circles correspond to the combined analysis which treats disjoint samples with exactly one NN $b$-tag and two secvtx tags separately.

Figure 7

Dijet mass distribution in $W+2$ jets events including exactly one secvtx $b$-tagged jet that passes the NN $b$-tagging filter. The contributions of the various background sources are shown in the histogram, while the hatched box on the background histogram represents the background uncertainty.

Figure 8

Dijet mass distribution in $W+2$ jets events including at least two secvtx $b$-tagged jets.

Figure 9

95% C.L. upper limit on $\sigma (p\overline{p}\to WH)·\mathcal{B}(H\to b\overline{b})$ with an integrated luminosity of $1{\mathrm{fb}}^{-1}$ obtained from the combined likelihood between events with exactly one secvtx $b$-tag passing the NN $b$-tagging and events with at least two secvtx $b$-tagged jets. The previous CDF data [7] and recent D0 data [8] are shown for comparison.

Figure 10

Results of 95% C.L. limits obtained from the combined likelihood in pseudoexperiments. The arrows indicate the observed limits.