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Abstract:
We report a search for standard model (SM) Higgs boson to WW* production
in the two charged lepton (e, mu) and two neutrino final state in p-pbar collisions
at sqrt(s) = 1.96 TeV. The data were collected with the CDF II detector at the
Tevatron collider at Fermilab and correspond to an integrated luminosity of roughly
4.8 fb-1. In order to maximize sensitivity, three neural networks are
separately trained to distinguish signal from background processes in final states
with either zero, one, or two or more jets. For 0-jet events, likelihood ratios
based on Matrix Element calculations are used as additional inputs to the neural
network to further strengthen its discriminating power. In order to take advantage
of the full signal acceptance, we also consider associated production with a W or
Z boson and Higgs boson production via vector boson fusion for final states with
one or more jets. Additional signal acceptance is gained by including events
with low dilepton invariant mass as a separate search region. We also search for
associated Higgs production in events with same sign dileptons in the final state.
In the opposite sign event sample we observe (summing over all jet multiplicities)
a total of 1567 candidate events compared against an expectation of 1550 ±
130 background events and 27 ± 5 signal events for a SM Higgs boson with
a mass of 165 GeV/c2. In the low dilepton invariant mass sample we
observe 85 candidate events compared against an expectation of 81 ± 7
background events and 0.8 ± 0.1 signal events for a SM Higgs boson with
a mass of 165 GeV/c2. In the same sign event sample we additionally
observe 81 candidate events compared with an expectation of 76 ± 13
background events and 1.9 ± 0.2 signal events for a SM Higgs boson with
a mass of 165 GeV/c2. Based on these samples, we determine an observed
95% C.L. upper cross section limit of 1.2 times the SM prediction at NNLL for a
Higgs mass of 165 GeV/c2 to be compared with the value for the median
of the expected limit (1.2). Results for thirteen other Higgs mass hypotheses
ranging from 110 GeV/c2 to 200 GeV/c2 are also presented.
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