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Unformatted text preview: and muons as well as the ET in events. The search
is based on the requirement that events contain two charged
leptons resulting from the decays of the ﬁnal-state vector
bosons which are OS except in the case of the VH channel
where they can be SS. At least one charged lepton is required
to match the lepton found in the trigger and have ET ðpT Þ >
20 GeV (GeV=c) for electrons (muons). The second charged
lepton is required to have ET ðpT Þ > 10 GeV (GeV=c) except
in events with same charge leptons, where both leptons are
required to have ET ðpT Þ > 20 GeV (GeV=c). Requirements
on the event ET indicative of the presence of neutrinos from
W boson decay are made in opposite-charge dilepton events.
Backgrounds due to Drell-Yan processes and heavy ﬂavor are 120 130 140 150 160 170 180 190 200 Higgs Mass (GeV) FIG. 66 (color online). Expected and observed upper limits at the
95% C.L. on H presented as a ratio to the predicted SM values as a
function of MH for the CDF H ! WW ðÃÞ analysis (Aaltonen et al.,
2010c). The dashed line represents the median expected limits, the
bands represent the estimated 1 and 2 probability bands for
the distribution of expectations, and the solid line represents the
observed limit. suppressed by requiring that the invariant mass of the lepton
pair be greater than 16 GeV=c2 . The Higgs-boson signature
can also involve jets of hadrons produced from the decay of
one of the vector bosons in the VH process, forward quarks in
the VBF process, or from the radiation of gluons.
In order to increase the sensitivity to the various Higgs
production processes in the SM, candidate events are subdivided into six analysis channels based on jet multiplicity,
lepton categories, and lepton charge combinations. Five of
the channels have signatures with OS leptons and the other is
for SS leptons.
Discrimination of signal from background is based on NNs
trained in each analysis channel and at each of 14 hypothesized mH values in the range 110 mH 200 GeV=c2 . The
NN inputs are based on kinematic quantities selected to
exploit features such as the spin correlation between the W
bosons in Higgs-boson decay, the presence of large ET from
the neutrinos; the transverse mass of the Higgs boson (calculated using the leptons’ four-momenta and ET vector); and
the modest total energy of the Higgs-boson decay products
compared to tt decay. In the zero jet categories, we additionally classify events by evaluating the observed kinematic
conﬁguration in a likelihood ratio of the signal probability
density divided by the sum of the signal and background
probability densities. These probability densities are determined from LO matrix element calculations of the cross TABLE XLI. Expected and observed upper limits at 95% C.L. for Higgs-boson production cross section expressed as a ratio to the cross
section predicted by the SM for a range of test Higgs-boson masses.
D0 (Abazov et al., 2010b)
CDF (Aaltonen et al....
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This document was uploaded on 09/28/2013.
- Fall '13