Measurement of Inclusive Radiative B -Meson Decay B -] X_s Gamma
Measurement of Inclusive Radiative B -Meson Decay B -] X_s Gamma

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Published: 2006

Total 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.

Radiative Decays of the B Meson
Radiative Decays of the B Meson

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Published: 2003

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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

Radiative B Meson Decay as a Probe of Physics Beyond the Standard Model
Radiative B Meson Decay as a Probe of Physics Beyond the Standard Model

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Published: 2009

Total Pages: 158

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The author presents measurements of radiative B meson decays to the final states Ks0[pi]0[gamma] and K[Phi][gamma] based on data collected at the [Upsilon](4S) resonance with the BABAR detector at the PEP-II e+e- collider at SLAC. In a data sample of 467 million B$\bar{B}$ pairs, the time-dependent CP asymmetry in B0 2!Ks0[pi]0[gamma] decays is measured in two regions of Ks0-[pi]0 invariant mass. In the K* region, 0.8

Studying B --] S Gamma at BABAR Using a Fully Inclusive Method
Studying B --] S Gamma at BABAR Using a Fully Inclusive Method

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Published: 2004

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The b [yields] s[gamma] decay represents a possible electromagnetic ''loop'' penguin decay of the B meson. This FCNC process is of high theoretical interest because various scenarios of new physics are expected to have contributions at the same (one loop) level as the Standard Model. The large sample of B[bar B] meson decays collected by the BaBar experiment makes a precision measurement of this rare decay possible. In conjunction with Standard Model predictions at the 10% level, it brings new physics effects into the realm of detection--or seriously constrains models that could predict them. A fully inclusive technique is presented to study the b [yields] s[gamma] transition as a function of photon energy, using 88.5 [+-] 1.0 x 10[sup 6] B[bar B] meson decays collected by the BaBar experiment in the years 2000 to 2002. The expected statistical and systematic uncertainties have been fully determined which enables first comparisons with theoretical predictions and other experimental results. It also lays the basis for the determination of the inclusive branching fraction [Beta](B [yields] X[sub s][gamma]) and the measurement of the photon energy spectrum.

Radiative and Leptonic B-meson Decays from the B-factories
Radiative and Leptonic B-meson Decays from the B-factories

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Published: 2011

Total 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.

Measurements of B -] V Gamma Decays
Measurements of B -] V Gamma Decays

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Published: 2010

Total Pages: 217

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The standard model has been highly successful at describing current experimental data. However, extensions of the standard model predict particles that have masses at energy scales that are above the electroweak scale. The flavor-changing neutral current processes of the B meson are sensitive to the influences of these new physics contributions. These processes proceed through loop diagrams, thus allowing new physics to enter at the same order as the standard model. New physics may contribute to the enhancement or suppression of rate asymmetries or the decay rates of these processes. The transition B → V[gamma] (V = K*(892), [rho](770), [omega](782), [phi](1020)) represents radiative decays of the B meson that proceed through penguin processes. Hadronic uncertainties limit the theoretical accuracy of the prediction of the branching fractions. However, uncertainties, both theoretical and experimental, are much reduced when considering quantities involving ratios of branching fractions, such as CP or isospin asymmetries. The most dominant exclusive radiative b → s transition is B → K*[gamma]. We present the best measurements of the branching fractions, direct CP, and isospin asymmetries of B → K*[gamma]. The analogous b → d transitions are B → [rho][gamma] and B → [omega][gamma], which are suppressed by a factor of.