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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 approximately 8.2 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 maximum potential signal acceptance, we also consider associated
production with a W or Z boson and Higgs boson production via vector boson
fusion. 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 and
trileptons in the final state. In the opposite-sign event sample we
observe (summing over all jet multiplicities) a total of 3513 candidate
events compared against an expectation of 3409 ± 233 background
events and 53.6 ± 9.4 signal events for a SM Higgs boson with a mass
of 165 GeV/c2. In the opposite-sign low dilepton invariant mass
sample we observe 260 candidate events compared against an expectation
of 262 ± 21 background events and 3.42 ± 0.52 signal events for a SM
Higgs boson with a mass of 165 GeV/c2. In the same-sign event sample
we additionally observe 224 candidate events compared with an expectation
of 198 ± 49 background events and 3.13 ± 0.42 signal events for a
SM Higgs boson with a mass of 165 GeV/c2. In the trilepton event
sample we observe 71 candidate events compared with an expectation of
63.6 ± 4.9 background events and 2.14 ± 0.19 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 production limit of 0.77 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 (0.78). Results
for eighteen other Higgs mass hypotheses ranging from 110 GeV/c2 to
200 GeV/c2 are also presented. We exclude at the 95% C.L. a SM Higgs
boson in the mass range between 156 and 175 GeV/c2.
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