Measurement of the B meson Lifetimes with the Collider Detector at Fermilab Page: 3 of 178

                                
Abstract

The lifetimes of the B-, B0 and B  mesons are measured using partially
reconstructed semileptonic decays. Following semileptonic decay processes and
their charge conjugates are used for this analysis:
B-/B0   -   t-vD0X
B-/B    -   t-vD*+X
B       E -vDs X ,
where f- denotes either a muon or electron.
The data are collected during 2002 - 2004 by the 8 GeV single lepton triggers
in CDF Run II at the Fermilab Tevatron Collider. Corresponding integrated
luminosity is about 260 and 360 pb-1 used for the B-/B0 and B  lifetime
analyses, respectively. With the single lepton triggers, events which contain
a muon or electron with a transverse momentum greater than 8 GeV/c are
selected. For these lepton candidates, further lepton identification cuts are
applied to improve purity of the B semileptonic decay signal.
After the lepton selection, three types of charm mesons associated with the
lepton candidates are reconstructed. Following exclusive decay modes are used
for the charm meson reconstruction:
D         K-r+
D*+      D0<s , followed by D0     K--+
DS   -   0-F+ , followed by #   K+K- .
Here -F denotes a slow pion from D*+ decay. Species of the reconstructed
charm meson identify the parent B meson species. However in the B-/B0
semileptonic decays, both mesons decay into the identical lepton+D  final
state. To solve this mixture of the B components in the D0 sample, we adopt
the following method: First among the inclusive D0 sample, we look for the
D*+ -  D0<F signal. The inclusive D0 sample is then split into the two samples
of D0 mesons which are from the D*+ meson and not from D*+. We use the
fact that D*+ sample is dominated by the B0 component, and the D0 sample
after excluding the D*+ events is dominated by the B- component. Fraction
of remaining mixture of B-/B0 components in each sample is estimated using
a Monte Carlo simulation.
From the lepton + charm meson pairs, we measure the B meson decay
lengths to extract the lifetimes. Since the B meson momentum, necessary to
calculate the B meson decay time, is not fully reconstructed in semileptonic