Measurement of the B̄→D*lν̄ branching fractions and -Vcb-

• Main Authors: BARISH, B.; et al., THULASIDAS, M.
• Format: text
• Language: English
• Published: Institutional Knowledge at Singapore Management University 1995
• Subjects: Computer Engineering; Databases and Information Systems
• Online Access: https://ink.library.smu.edu.sg/sis_research/5796
• Institution: Singapore Management University

We study the exclusive semileptonic B meson decays B−→D*0l−ν¯ and B¯0→D*+l−ν¯ using data collected with the CLEO II detector at the Cornell Electron-positron Storage Ring (CESR). We present measurements of the branching fractions scrB(B¯0→D*+l−ν¯)= (0.5/f00)[4.49±0.32(stat.)±0.39 (syst.)]% and scrB(B−→D*0l−(ν¯)= (0.5/f+−)[5.13±0.54 (stat) ±0.64 (syst)]%, where f00 and f+− are the neutral and charged B meson production fractions at the Υ(4S) resonance, respectively. Assuming isospin invariance and taking the ratio of charged to neutral B meson lifetimes measured at higher energy machines, we determine the ratio f+−/f00=1.04±0.13 (stat) ±0.12 (syst) ±0.10 (lifetime); further assuming f+−+f00=1 we also determine the partial width Γ(B¯→D*lν¯)=[29.9±1.9 (stat) ±2.7 (syst.) ±2.0 (lifetime)] ns−1 (independent of f+−/f00).From this partial width we calculate B¯→D*lν¯ branching fractions that do not depend on f+−/f00 or the individual B lifetimes, but only on the charged to neutral B lifetime ratio. The product of the CKM matrix element ‖Vcb‖ times the normalization of the decay form factor at the point of no recoil of the D* meson, scrF(y=1), is determined from a linear fit to the combined differential decay rate of the exclusive B¯→D*lν¯ decays: ‖Vcb‖scrF(1)=0.0351±0.0019 (stat) ±0.0018 (syst) ±0.0008 (lifetime). The value for ‖Vcb‖ is extracted using theoretical calculations of the form factor normalization.