Author:
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Category :
Languages : en
Pages : 9

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Author:
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ISBN:
Category :
Languages : en
Pages : 312

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We present the results of a search for B+ meson decays into [gamma]l+vl, where l = e, [mu]. We use a sample of 232 million B$\bar{B}$ meson pairs recorded at the [Upsilon](4S) resonance with the BABAR detector at the PEP-II B factory. We measure a partial branching fraction [Delta][beta] in a restricted region of phase space that reduces the effect of theoretical uncertainties, requiring the lepton energy to be in the range 1.875 and 2.850 GeV, the photon energy to be in the range 0.45 and 2.35 GeV, and the cosine of the angle between the lepton and photon momenta to be less than -0.36, with all quantities computed in the [Upsilon](4S) center-of-mass frame. We find [Delta][beta](B+ 2![gamma]l+vl) = ( -0.31.5+1.3(statistical) -0.6+0.6(systematic) ± 0.1(theoretical)) x 10-6, under the assumption of lepton universality. Interpreted as a 90% confidence-level Bayesian upper limit, the result corresponds to 1.7 x 10-6 for a prior at in amplitude, and 2.3 x 10-6 for a prior at in branching fraction.

Author: Chaoxi Chang
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Category :
Languages : en
Pages :

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Author:
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Category :
Languages : en
Pages : 7

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Radiative and leptonic decays of B-mesons represent an excellent laboratory for the search for New Physics. I present here recent results on radiative and leptonic decays from the Belle and BABAR collaborations. Radiative penguin and leptonic B-meson decays are excellent probes for investigating the effects of New Physics. Although current measurements are in agreement with the Standard Model expectations, they are still quite useful for setting bounds on possible NP models. The B → X{sub s}[gamma] and B → [tau][nu] measurements, for example, put strong constraints on the mass of charged Higgs bosons in Type II two-Higgs double models. The B → X{sub s}[gamma] branching fraction measurements also constrain models with universal extra dimensions.

Author: Y. Ushiroda
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ISBN:
Category :
Languages : en
Pages : 4

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Author: Jennifer Mutschall
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Category :
Languages : en
Pages : 138

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Author: BELLE
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Category :
Languages : en
Pages : 15

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Author:
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ISBN:
Category :
Languages : en
Pages :

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The radiative decays of the B meson to the final states K*(892)[gamma] and[rho](770)[gamma] proceed through virtual effective flavor-changing neutral current processes which are sensitive to contributions from high mass scales from within the Standard Model of particle interactions and from possible new physics. In the context of the Standard Model, these transitions are of interest in probing the weak interaction behavior of the top quark. In particular, the ratio of branching fractions for the two processes can be used to extract the ratio of Cabibbo-Kobayashi-Maskawa matrix elementsV[sub td]/V[sub ts]. Potential new physics contributions in these virtual transitions may induce new sources of direct CP violation and enhancement or suppression of the rate of these processes. The B[yields] K*[gamma] is a manifestation of the b[yields] s[gamma] radiative transition. This process has been previously observed by the CLEO collaboration and its branching fraction measured. While the theoretical prediction for the inclusive rate of b[yields] s[gamma] transitions is more robust than that of the exclusive B[yields] K*[gamma], the prospects for precise measurements of[Beta][B[yields] K*[gamma]] and direct CP violation in this channel has attracted considerable attention. The analysis described here represents an improved measurement of the B[yields] K*[gamma] branching factions and a more sensitive search for direct CP violation. In 22.7 x 10[sup 6] B[bar B] events collected by the BABAR detector in 1999-2000, we measure:[Beta][B[sup 0][yields] K*[sup 0][gamma]]= 4.23[+-] 0.40(stat.)[+-] 0.22(syst.) x 10[sup -5] and[Beta][B[sup+][yields] K*[sup+][gamma]]= 3.83[+-] 0.62(stat.)[+-] 0.22(syst.) x 10[sup -5]. We find no evidence for direct CP violation in the decays and constrain -0.170

Author:
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ISBN:
Category :
Languages : en
Pages : 206

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Radiative decays of the B meson, B 2!X{sub s}[gamma], proceed via virtual flavor changing neutral current processes that are sensitive to contributions from high mass scales, either within the Standard Model of electroweak interactions or beyond. In the Standard Model, these transitions are sensitive to the weak interactions of the top quark, and relatively robust predictions of the inclusive decay rate exist. Significant deviation from these predictions could be interpreted as indications for processes not included in the minimal Standard Model, like interactions of charged Higgs or SUSY particles. The analysis of the inclusive photon spectrum from B 2!X{sub s}[gamma] decays is rather challenging due to high backgrounds from photons emitted in the decay of mesons in B decays as well as ee− annihilation to low mass quark and lepton pairs. Based on 88.5 million B{bar B} events collected by the BABAR detector, the photon spectrum above 1.9 GeV is presented. By comparison of the first and second moments of the photon spectrum with QCD predictions (calculated in the kinetic scheme), QCD parameters describing the bound state of the b quark in the B meson are extracted: m{sub b} = (4.45 ± 0.16) GeV/c2; [mu]{sub {pi}}2 = (0.65 ± 0.29) GeV2. These parameters are useful input to non-perturbative QCD corrections to the semileptonic B decay rate and the determination of the CKM parameter.

Author:
Publisher:
ISBN:
Category : Nuclear energy
Languages : en
Pages : 612

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