Determining Gamma(b ---> ul Nu)/gamma(b ---> CL Nu) from the End-Point Region of the Lepton Momentum Spectrum in B-Meson Decay.
Abstract
An upper limit is placed on Gamma (b to ulnu)/ Gamma(b to c lnu) from lepton production in the end-point region of the lepton momentum spectrum in semileptonic B-meson decay. The B mesons are produced at the Upsilon(4S) resonance from e^ {+}e^{-} annihilations at the Cornell Electron Storage Ring (CESR). The CLEO detector is used to study B-meson semileptonic decay processes. Methods of reducing the continuum background are employed to determine the lepton contribution from B mesons at the upper end of the momentum spectrum. The method of finding Gamma (b to ulnu)/Gamma(b to clnu) has only a small dependence upon the b to clnu model and can be expressed explicitly in terms of the b to ulnu model. If f _{rm u}(2.3) is the fraction of leptons from b to u lnu in the momentum range from 2.3 -2.6 GeV/c, then Gamma({rm b} to {rm u}lnu) over Gamma({rm b}to {rm c}lnu) = (0.000 +/- 0.011) (0.115over{rm f }_{rm u}(2.3) - 0.002). For the various b to {rm u}l nu models considered here, f_ {rm u}(2.3) ranges from 0.0750 to 0.1584, corresponding to 90% confidence level upper limits for Gamma(b to ulnu)/Gamma(b to clnu) between 0.027 and 0.013. These limits are converted into limits on the ratio of the Kobayashi-Maskawa matrix elements V _{rm ub} and V _{rm cb} and are found to range from 0.08 to 0.15. The implications of these limits on the standard model are discussed.
- Publication:
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Ph.D. Thesis
- Pub Date:
- September 1987
- Bibcode:
- 1987PhDT........89G
- Keywords:
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- Physics: Elementary Particles and High Energy