Measurement of B \to X \gamma Decays and Determination of PDF Download

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Languages : en
Pages : 7

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Using a sample of 383 million B{bar B} events collected by the BABAR experiment, they measure sums of seven exclusive final states B → X{sub d(s)}[gamma], where X{sub d}(X{sub s}) is a non-strange (strange) charmless hadronic system in the mass range 0.6-1.8 GeV/c2. After correcting for unmeasured decay modes in this mass range, they obtain a branching fraction for b → d[gamma] of (7.2 ± 2.7(stat.) ± 2.3(syst.)) x 10−6. Taking the ratio of X{sub d} to X{sub s} they find [Lambda](b → d[gamma])/[Lambda](b → s[gamma]) = 0.033 ± 0.013(stat.) ± 0.009(syst.), from which they determine.

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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: B. Aubert
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Languages : en
Pages : 15

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We measure the branching fraction of the radiative B{sup -} decay {Beta}(B{sup -} {yields} {phi}K{sup -}{gamma}) = (3.46 {+-} 0.57{sub -0.37}{sup +0.39}) x 10{sup -6}, and set an upper limit on the radiative {bar B}{sup 0} decay {Beta}({bar B}{sup 0} {yields} {phi}{bar K}{sup 0}{gamma})

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Languages : en
Pages : 7

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Using a sample of 471 million B{bar B} events collected with the BABAR detector, we study the sum of seven exclusive final states B → X{sub s(d)[gamma]}, where X{sub s(d)} is a strange (non-strange) hadronic system with a mass of up to 2.0 GeV/c2. After correcting for unobserved decay modes, we obtain a branching fraction for b → d[gamma] of (9.2 ± 2.0(stat.) ± 2.3(syst.)) x 10−6 in this mass range, and a branching fraction for b → s[gamma] of (23.0 ± 0.8(stat.) ± 3.0(syst.)) x 10−5 in the same mass range. We find [Beta](b→d[gamma])/[Beta](b→s{gamma}) = 0.040 ± 0.009(stat.) ± 0.010(syst.), from which we determine.

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Languages : en
Pages : 8

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The photon spectrum in B 2!X{sub s}[gamma] decay, where X{sub s} is any strange hadronic state, is studied using a data sample of 88.5 x 106 ee− 2 2!B{bar B} decays collected by the BABAR experiment at SLAC. The partial branching fraction, [Delta][Beta](B 2!X{sub s}[gamma]) = (3.67 ± 0.29(stat.) ± 0.34(sys.) ± 0.29(model)) x 10−4, the first moment E{sub {gamma}} = 2.288 ± 0.025 ± 0.017 ± 0.015 GeV and the second moment E{sub {gamma}}2 = 0.0328 ± 0.0040 ± 0.0023 ± 0.0036 GeV2 are measured for the photon energy range 1.9 GeV E{sub {gamma}}

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Languages : en
Pages : 3

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We present measurements of the Branching Fraction and photon energy spectrum in B → X{sub S}[gamma] decays in a sample of 89 million B{bar B} pairs collected at the BABAR detector at Stanford Linear Accelerator Center's PEP-II asymmetric B-factory. Results from a fully-inclusive and a sum of 38 exclusive final states techniques are presented and found to be consistent with the Standard Model calculations, as well as experimental results obtained from semileptonic B → X{sub c}lv decays.

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Languages : en
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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.

Author: B. Aubert
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Languages : en
Pages : 7

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The authors present measurements of the B {yields} {eta}K{gamma} branching fractions and upper limits for the B {yields} {eta}'K{gamma} branching fractions. For B{sup +} {yields} {eta}K{sup +}{gamma} they also measure the time-integrated charge asymmetry. The data sample, collected with the BABAR detector at the Stanford Linear Accelerator Center, represents 232 x 10{sup 6} produced B{bar B} pairs. The results for branching fractions and upper limits at 90% C.L. in units of 10{sup -6} are: {Beta}(B{sup 0} {yields} {eta}K{sup 0}{gamma}) = 11.3{sub -2.6}{sup +2.8} {+-} 0.6, {Beta}(B{sup +} {yields} {eta}K{sup +}{gamma}) = 10.0 {+-} 1.3 {+-} 0.5, {Beta}(B{sup 0} {yields} {eta}'K{sup 0}{gamma})

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Languages : en
Pages : 9

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We present a measurement of the branching fraction and photon energy spectrum for the decay B → X{sub s}[gamma] using data from the BABAR experiment. The data sample corresponds to an integrated luminosity of 210 fb−1, from which approximately 680,000 B{bar B} events are tagged by a fully reconstructed hadronic decay of one of the B mesons. In the decay of the second B meson, an isolated high-energy photon is identified. We measure [Beta](B → X{sub s}[gamma]) = (3.66 ± 0.85{sub stat} ± 0.60{sub syst}) x 10−4 for photon energies E{sub {gamma}} above 1.9 GeV in the B rest frame. From the measured spectrum we calculate the first and second moments for different minimum photon energies, which are used to extract the heavy-quark parameters m{sub b} and [mu]{sub {pi}}2. In addition, measurements of the direct CP asymmetry and isospin asymmetry are presented.

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Languages : en
Pages : 8

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The authors search for the decays B− →?K−? and {bar B}° →?{bar K}°? in a data sample of 228 million B{bar B} pairs collected at the?(4S) resonance with the BABAR detector. They measure the branching fraction?(B− →?K−?) = (3.5 ± 0.6 ± 0.4) x 10−6 and set an upper limit?({bar B}° →?{bar K}°?)