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| Author | : Torsten Leddig |
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| Total Pages | : 0 |
| Release | : 2015 |
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| Author | : Torsten Leddig |
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| Total Pages | : 90 |
| Release | : 2014 |
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| Total Pages | : 7 |
| Release | : 2012 |
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We present a search for semileptonic B decays to the charmed baryon [Lambda]{sub c} based on 420 fb−1 of data collected at the [Upsilon](4S) resonance with the BABAR detector at the PEP-II e+e− storage rings. By fully reconstructing the recoiling B in a hadronic decay mode, we reduce non-B backgrounds and determine the flavor of the signal B. We statistically correct the flavor for the effect of the B° mixing. We obtain a 90% confidence level upper limit of [Beta]({bar B} 2![Lambda]{sub c}+ Xl− {bar [nu]}{sub l})/[Beta]({bar B} 2![Lambda]{sub c}+ X)
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| Total Pages | : 10 |
| Release | : 2008 |
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We present a search for the decays B → K*?{bar?} using 454 x 106 B{bar B} pairs collected at the?(4S) resonance with the BABAR detector at the SLAC PEP-II B-Factory. We first select an event sample where one B is reconstructed in a semileptonic or hadronic mode with one charmed meson. The remaining particles in the event are then examined to search for a B → K*?{bar?} decay. The charged K* is reconstructed as K* → K{sub S}°?+ or K*+ → K+?°; the neutral K* is identified in K*° → K+?− mode. We establish upper limits at 90% confidence level of?(B+ → K*+?{bar {nu}})
| Author | : Dana Lindemann |
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| Release | : 2012 |
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"This thesis presents the searches for two rare B meson decays: the radiative leptonic decay B+ -> l+ nu gamma (l = e, mu) and the flavor-changing neutral current B -> K(*) nu nubar. These searches use the full dataset collected by the BaBar experiment, which corresponds to almost 500 million BB pairs. After fully reconstructing the hadronic decay of one of the B mesons in Upsilon(4S) -> BB decays, evidence of B+ -> l+ nu gamma or B -> K(*) nu nubar is looked for in the rest of the event. No significant evidence of either signal decay is observed. Model-independent branching-fraction upper limits are set at BR(B ->e nu gamma)17 x10 {-6}, BR(B -mu nu gamma)24 x10 {-6}, and BR(B -l nu gamma)15.6 x10 {-6}, all at the 90% confidence level. These are currently the most stringent published upper limits for B+ - l+ nu gamma. In addition, branching-fraction upper limits are set at BR(B -> K+ nu nubar)3.7 x10 {-5}, BR(B - K0 nu nubar)8.0 x10 {-5}, BR(B - K*+ nu nubar)11.5 x10 {-5}, and BR(B - K*0 nu nubar)9.2 x10 {-5}, all at the 90% confidence level. For additional sensitivity to New Physics contributions, partial B - K(*) nu nubar branching-fraction upper limits are also determined over the full kinematic range." --
| Author | : Robert Seddon |
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| Release | : 2019 |
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"We present two analyses of the rare B- -> Lambda pbar nu nubar decay. Within the Standard Model, the process B- -> Lambda pbar nu nubar is permitted but highly suppressed, with an expected branching fraction of (7.9 +/- 1.9) x 10^-7. This rarity makes it a sensitive probe for the existence of new physics, which may be discoverable in the form of a higher than predicted branching fraction.The first analysis is conducted on data collected at the BABAR experiment, which ran from 1999-2008. BABAR collected 433 fb^-1 of integrated luminosity at the Upsilon(4S) resonance; Upsilon(4S) decays almost exclusively into B-Bbar pairs, and this analysis uses hadronic tag reconstruction to fully reconstruct one of the B-mesons in this pair. The search for B- -> Lambda pbar nu nubar is then conducted among the decay products of the second, unreconstructed B-meson. Using both real data and Monte Carlo simulations, we develop and implement a signal selection that selects candidates conforming to the expected characteristics of B- -> Lambda pbar nu nubar decays. The result of the analysis is an upper limit on the branching fraction at the 90% confidence level of 3.02 x 10^-5. This is the world's first experimental result in the search for B- -> Lambda pbar nu nubar decays.The second analysis is conducted on Monte Carlo simulations of data that will be collected at Belle II, the world's only next-generation B-meson facility. Over its lifetime Belle II will collect 50 ab^-1 of data, approximately 100 times that of BABAR. This increase in data, along with more capable hardware and software, should allow Belle II to search for B- -> Lambda pbar nu nubar decays with greater sensitivity than BABAR. Using a simulated dataset equivalent in size to that used in our BABAR study, we employ Full Event Interpretation to fully reconstruct the decay of one B-meson in each B-Bbar pair, and conduct our signal selection in the remainder of the data. The result of the analysis is a predicted upper limit on the branching fraction at the 90% confidence level of 1.2 x 10^-4. A comparison of the Belle II and BABAR results highlights several areas where Belle II will need to improve in order to make best use of its projected dataset"--
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| Total Pages | : 7 |
| Release | : 2009 |
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The authors report the observation of the baryonic B-decay {bar B}° → ?{sub c}+{bar p}K−?+, excluding contributions from the decay {bar B}° → ?{sub c}+{bar ?}K−. Using a data sample of 467 million B{bar B} pairs collected with the BABAR detector at the PEP-II storage ring at SLAC, the measured branching fraction is (4.33 ± 0.82){sub stat} ± 0.33{sub syst} ± 1.13{sub ?{sub c}+} x 10−5. In addition they find evidence for the resonant decay {bar B}° → ?{sub c}(2455){sup ++}{bar p}K− and determine its branching fraction to be (1.11 ± 0.30{sub stat} ± 0.09{sub syst} ± 0.29{sub ?{sub c}+}) x 10−5. The errors are statistical, systematic, and due to the uncertainty in the ?{sub c}+ branching fraction. For the resonant decay {bar B}° → ?{sub c}+{bar p}{bar K}*° we obtain an upper limit of 2.42 x 10−5 at 90% confidence level.
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| Total Pages | : 7 |
| Release | : 2010 |
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In a sample of 467 million B{bar B} pairs collected with the BABAR detector at the PEP-II collider at SLAC we have observed the decay {bar B}° →?{sub c}{bar p}?° and measured the branching fraction to be (1.94 ± 0.17 ± 0.14 ± 0.50) x 10−4, where the uncertainties are statistical, systematic, and the uncertainty on the?{sub c}+ → pK−?+ branching fraction, respectively. We determine an upper limit of 1.5 x 10−6 at 90% C.L. for the product branching fraction?({bar B}° →?{sub c}+(2455){bar p}) x?(?{sub c}+ → pK−?+). Furthermore, we observe an enhancement at the threshold of the invariant mass of the baryon-antibaryon pair.
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| Release | : 2010 |
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We measure the branching fraction of the exclusive charmless semileptonic decay B 2![omega]l[nu]{sub l}, where l is either an electron or a muon, with the charged B meson recoiling against a tag B meson decaying in the charmed semileptonic modes B 2!Dl[nu]{sub {ell}} or B 2!D*{ell}[nu]{sub {nu}}. The measurement is based on a dataset of 426.1 fb−1 of ee− collisions at a CM energy of 10.58 GeV recorded with the BABAR detector at the PEP-II asymmetric B Factory located at the SLAC National Accelerator Laboratory. We also calculate the relevant B 2![omega] hadronic form factors to determine the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element.
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| Total Pages | : 7 |
| Release | : 2011 |
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The authors report the observation of the baryonic B decay {bar B}° 2![Lambda]{sub c} {bar [Lambda]}K− with a significance larger than 7 standard deviations based on 471 x 106 B{bar B} pairs collected with the BABAR detector at the PEP-II storage ring at SLAC. They measure the branching fraction for the decay {bar B}° 2![Lambda]{sub c}+ {bar [Lambda]}K− to be (3.8 ± 0.8{sub stat} ± 0.2{sub sys} ± 1.0 {sub {Lambda}{sub c}+}) x 10−5. The uncertainties are statistical, systematic, and due to the uncertainty in the {Lambda}{sub c}+ branching fraction. They find that the {Lambda}{sub c}+ K− invariant mass distribution shows an enhancement above 3.5 GeV/c2.
