We present the results of a search for the top quark in 19.3 pb^{-1}
of p pbar
collisions at sqrt{s}= 1.8 TeV. The data were collected
at the Fermilab Tevatron collider using the Collider Detector at
Fermilab (CDF). The search includes Standard Model
t tbar
decays to
final states
e e nu nubar,
e mu nu nubar,
and
mu mu nu nubar
as well as
e + nu + jets
or
mu + nu + jets.
In the
(e, mu) + nu + jets
channel we search for b quarks from t
decays via secondary-vertex identification and via semileptonic
decays of the b and cascade c
quarks. In the dilepton final states
we find two events with a background of 0.56^{+0.25}_{-0.13} events.
In the e, mu + nu + jets channel with a b
identified
via a secondary vertex, we find six events with a background of
2.3 +- 0.3. With a b identified via a semileptonic decay,
we find seven events with a background of 3.1 +- 0.3. The
secondary-vertex and semileptonic decay samples have
three events in common.
The probability that the observed yield is consistent with the
background is estimated to be 0.26%. The statistics are too
limited to firmly establish the existence of the top quark,
however a natural interpretation of the excess is that
it is due to t tbar production. We present several cross checks.
Some support this hypothesis, others do not. Under the assumption
that the excess yield over background is due to t tbar,
constrained fitting on a subset of the events yields a mass of
174 \pm 10^{+ 13}_{- 12} GeV/c^2
for the top quark. The t tbar cross section, using this
top quark mass to compute the acceptance, is measured to be
13.9^{+6.1}_{-4.8} pb.
PACS Numbers: 14.80.Dq, 13.85.Qk, 13.85.Ni