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The authors present a search for the decay B → l+?{sub l} (l =?,?, or e) in (458.9 ± 5.1) x 106 B{bar B} pairs recorded with the BABAR detector at the PEP-II B-Factory. They search for these B decays in a sample of B+B− events where one B-meson is reconstructed as B− → D°{ell}−{bar?}X. Using the method of Feldman and Cousins, they obtain?(B+ →?+?{sub {tau}}) = (1.7 ± 0.8 ± 0.2) x 10−4, which excludes zero at 2.3?. They interpret the central value in the context of the Standard Model and find the B meson decay constant to be f{sub B}2 = (62 ± 31) x 103 MeV2. They find no evidence for B+ → e+?{sub e} and B+ →?+?{sub?} and set upper limits at the 90% C.L.?(B+ → e+?{sub e})
We present a search for the decay B[sup+][yields][tau][sup+][nu][sub[tau]] in 88.9 x 10[sup 6][Upsilon](4S) decays recorded with the BABAR detector at the SLAC B-Factory. A sample of semi-exclusive, semi-leptonic B decays (B[sup -][yields] D[sup 0][ell][sup -][bar[nu]][sub[ell]]X), where X is either a photon, [pi][sup 0], or nothing, is used to identify the daughter particles that are associated with the other B meson in each event. These particles are searched for evidence of a one-prong leptonic B[sup+][yields][tau][sup+][nu][sub[tau]] decay. For this data sample we set a preliminary upper limit on the branching fraction of[Beta](B[sup+][yields][tau][sup+][nu][sub[tau]])
We present a search for the decay B{sup +} {yields} {tau}{sup +}{nu}{sub {tau}} in 88.9 x 10{sup 6} {Upsilon}(4S) decays recorded with the BABAR detector at the SLAC B-Factory. A sample of semi-exclusive, semi-leptonic B decays (B{sup -} {yields} D{sup 0}{ell}{sup -}{bar {nu}}{sub {ell}}X), where X is either a photon, {pi}{sup 0}, or nothing, is used to identify the daughter particles that are associated with the other B meson in each event. These particles are searched for evidence of a one-prong leptonic B{sup +} {yields} {tau}{sup +}{nu}{sub {tau}} decay. For this data sample we set a preliminary upper limit on the branching fraction of {Beta}(B{sup +} {yields} {tau}{sup +}{nu}{sub {tau}})
The fundamental pursuit of physics has always been a deeper understanding of nature's workings. In the last fifty years this pursuit has culminated in a view of the universe as a complex tapestry woven from only a few fundamental particles and interactions. This description of the universe, the Standard Model of Particle Physics, has been highly successful at predicting the behavior of these particles and interactions. However, the model leaves many questions unanswered and the hope is that many precise tests of its predictions will yield inconsistencies, windows into new physical principles. The search for processes that are allowed by the Standard Model but inherently rare provides fruitful ground for such a test. The large sample of B mesons available from the PEP-II/BABAR B-factory furnishes an opportunity to test Standard Model predictions via rare B meson decay modes.
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The authors present a search for the decay B -->?+?{sub?} in 124.1 x 106?(4S) decays recorded with the BABAR detector at the SLAC PEP-II B-Factory. A sample of events with one reconstructed exclusive semi-leptonic B decay (B− --> D*°l−{bar?}{sub {ell}}) is selected, and in the recoil a search for B+ -->?+?{sub?} signal is performed. The? is identified in the following channels:?+ --> e+?{sub e}{bar?}{sub?} -->?+?{sub {mu}}{bar?}{sub?},?+ -->?+{bar {nu}}{sub?}, {tau}+ -->?+?°{bar {nu}}{sub {tau}}, {tau}+ -->?+?−?+{bar {nu}}{sub {tau}}. The authors find no evidence of signal, and they set a preliminary upper limit on the branching fraction of B(B+ --> {tau}+{nu}{sub {tau}}) 4.3 x 10−4 at the 90% confidence level (CL). This result is then combined with a statistically independent BABAR search for B+ -- {tau}+{nu}{sub {tau}} to give a combined preliminary limit of B(B+ --> {tau}+{nu}{sub {tau}})
We present a search for the decay B → l+?{sub l} (l =?,?, or e) in (458.9 ± 5.1) x 106?(4S) decays recorded with the BABAR detector at the SLAC PEP-IIB-Factory. A sample of events with one reconstructed exclusive semi-leptonic B decay (B− → D° l−{bar?}X) is selected, and in the recoil a search for B+ → {ell}+?{sub {ell}} signal is performed. The? is identified in the following channels:?+ → e+?{sub e}?{sub?},?+ →?+?{sub?}?{sub?},?+ →?+?{sub?}, and {tau}+ →?+?°?{sub {tau}}. The analysis strategy and the statistical procedure is set up for branching fraction extraction or upper limit determination. We determine from the dataset a preliminary measurement of?(B+ → {tau}+?{sub {tau}}) = (1.8 ± 0.8 ± 0.1) x 10−4, which excludes zero at 2.4?, and f{sub B} = 230 ± 57 MeV. Combination with the hadronically tagged measurement yields?(B+ → e+?{sub e}) = (1.8 ± 0.6) x 10−4. We also set preliminary limits on the branching fractions at?(B+ → e+?{sub e})
We present a search for the decay B →?+?{sub?} using 288 fb−1 of data collected at the?(4S) resonance with the BABAR detector at the SLAC PEP-II B-Factory. A sample of events with one reconstructed semileptonic B decay (B− → D{sup o}l−{bar?}{sub {ell}}X) is selected, and in the recoil a search for B+ →?+?{sub?} signal is performed. The? is identified in the following channels:?+ → e+?{sub e}{bar?}{sub?},?+ →?+?{sub {mu}}{bar {nu}}{sub {tau}}, {tau}+ →?+?°{bar {nu}}{sub {tau}}. We measure a branching fraction of?(B+ → {tau}+{nu}{sub {tau}}) = 0.88{sub -0.67}{sup +0.68}(stat.) ± 0.11(syst.) x 10−4 and extract an upper limit on the branching fraction, at the 90% confidence level, of?(B+ → {tau}+{nu}{sub {tau}})