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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
5.9 fb-1. In order to maximize sensitivity, three neural networks are
separately trained to distinguish signal from background processes in opposite-sign
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 incorporating 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 2070 candidate
events compared against an expectation of 2108 ± 190 background events and 36
± 7 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 112 candidate events
compared against an expectation of 112 ± 9 background events and 1.0 ±
0.2 signal events for a SM Higgs boson with a mass of 165 GeV/c2. In the
same-sign event sample we additionally observe 74 candidate events compared with an
expectation of 75 ± 15 background events and 2.1 ± 0.3 signal events
for a SM Higgs boson with a mass of 165 GeV/c2. In the trilepton event
sample we observe 53 candidate events compared with an expectation of 42 ±
5 background events and 1.5 ± 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 1.08 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 (1.00). Results for 18 other Higgs mass hypotheses ranging
from 110 GeV/c2 to 200 GeV/c2 are also presented.
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