Measurement of the B meson Lifetimes with the Collider Detector at Fermilab
- Univ. of Tsukuba (Japan)
The lifetimes of the B-, $$\bar{B}$$0 and $$\bar{B}$$$$0\atop{s}$$ mesons are measured using partially reconstructed semileptonic decays. Following semileptonic decay processes and their charge conjugates are used for this analysis: B-/B0 → ℓ-vD0X; B-/B0 → ℓ-vD*+X; B$$0\atop{s}$$ → ℓ-vD $$+\atop{s}$$x, where ℓ- 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 pbℓ-1 used for the B-/B0 and B$$0\atop{s}$$ 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: D0 → K-π+; D*+ → D0π$$+\atop{s}$$, followed by D0→ K-π+; D$$+\atop{s}$$ → Φπ++K-. Here π$$+\atop{s}$$ 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 + D0 final state. To solve this mixture of the B components in the D0 sample, they adopt the following method: First among the inclusive D0 sample, they look for the D*+ → D0 π$$+\atop{s}$$ 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*+. They 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, they 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 decays, the missing momentum is corrected using a Monte Carlo simulation during lifetime fits.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-07CH11359
- OSTI ID:
- 948152
- Report Number(s):
- FERMILAB-THESIS-2006-78; TRN: US0901566
- Country of Publication:
- United States
- Language:
- English
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