Measurement of the B Semileptonic Branching Fraction with Lepton Tags

Creators: Barish, B.; Chadha, M.; Chan, S.; Eigen, G.; Miller, J. S.; O'Grady, C.; Urheim, J.; Würthwein, F.; Weinstein, Alan J.; CLEO Collaboration

Abstract

We have used the CLEO II detector and 2.06fb^(-1) of ϒ(4S) data to measure the B-meson semileptonic branching fraction. The B→Xeν momentum spectrum was obtained over nearly the full momentum range by using charge and kinematic correlations in events with a high-momentum lepton tag and an additional electron. We find B(B→Xeν) = (10.49±0.17±0.43)%, with overall systematic uncertainties less than those of untagged single-lepton measurements. We use this result to calculate the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element V_(cb) and to set an upper limit on the fraction of ϒ(4S) decays to final states other than BB̅ .

Additional Information

© 1996 The American Physical Society. Received 16 October 1995; published in the issue dated 4 March 1996. We are grateful to the CESR staff for providing excellent luminosity and running conditions. We thank A. Vainshtein and M. Shifman for stimulating discussions. This work was supported by the National Science Fundation, the U.S. Department of Energy, the Heisenberg Foundation, the Alexander von Humboldt Stiftung, the Natural Sciences and Engineering Research Council of Canada, and the A.P. Sloan Foundation.

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