Preliminary Measurement of the Inclusive Electron Spectrum in Charmless Semileptonic B Decays Near the Kinematic Endpoint and Determination of [verticalV[sub Ub][vertical PDF Download
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The authors study the inclusive electron spectrum of B --> X[sub u]e[nu] decays near the kinematic limit for B --> X[sub c]e[nu] transitions using a sample of 88 million [Upsilon](4S) decays recorded by the BABAR detector at the PEP II e[sup +]e[sup -] storage rings. For the electron momentum interval of 2.0-2.6GeV/c the partial branching fraction is measured to be [Delta]B(B --> X[sub u]e[nu]) = (0.480 [+-] 0.029(stat) [+-] 0.053(syst) x 10[sup -3]). Combining this result on [Delta]B with measurements of the inclusive photon spectrum in B --> X[sub s][gamma] transition the authors find V[sub ub] = 3.94 [+-] 0.25exp [+-] 0.37 f[sub u] [+-] 0.19 theory x 10[sup -3], where the first error represents the combined statistical and systematic experimental uncertainty of the partial branching fraction measurement, the second refers to the uncertainty of the determination of the fraction f[sub u] of the inclusive electron spectrum that falls within the cuts, and the third error is due to theoretical uncertainties in the QCD corrections, plus the uncertainty in the b-quark mass. All results are preliminary.
![Preliminary Measurement of the Inclusive Electron Spectrum in Charmless Semileptonic B Decays Near the Kinematic Endpoint and Determination of [verticalV[sub Ub][vertical PDF](https://books.google.com/books/content/images/frontcover/BhkJkAEACAAJ?fife=w80-h100)
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The authors study the inclusive electron spectrum of B --> X[sub u]e[nu] decays near the kinematic limit for B --> X[sub c]e[nu] transitions using a sample of 88 million [Upsilon](4S) decays recorded by the BABAR detector at the PEP II e[sup +]e[sup -] storage rings. For the electron momentum interval of 2.0-2.6GeV/c the partial branching fraction is measured to be [Delta]B(B --> X[sub u]e[nu]) = (0.480 [+-] 0.029(stat) [+-] 0.053(syst) x 10[sup -3]). Combining this result on [Delta]B with measurements of the inclusive photon spectrum in B --> X[sub s][gamma] transition the authors find V[sub ub] = 3.94 [+-] 0.25exp [+-] 0.37 f[sub u] [+-] 0.19 theory x 10[sup -3], where the first error represents the combined statistical and systematic experimental uncertainty of the partial branching fraction measurement, the second refers to the uncertainty of the determination of the fraction f[sub u] of the inclusive electron spectrum that falls within the cuts, and the third error is due to theoretical uncertainties in the QCD corrections, plus the uncertainty in the b-quark mass. All results are preliminary.
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Pages : 5
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The authors study the inclusive electron spectrum of B --> X{sub u}e[nu] decays near the kinematic limit for B --> X{sub c}e[nu] transitions using a sample of 88 million [Upsilon](4S) decays recorded by the BABAR detector at the PEP II ee− storage rings. For the electron momentum interval of 2.0-2.6GeV/c the partial branching fraction is measured to be [Delta]B(B --> X{sub u}e[nu]) = (0.480 ± 0.029(stat) ± 0.053(syst) x 10−3). Combining this result on [Delta]B with measurements of the inclusive photon spectrum in B --> X{sub s}[gamma] transition the authors find.
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A preliminary result on the study of the inclusive electron spectrum in B[yields] X[sub u]e[nu] decays above the kinematic limit for the dominant B[yields] X[sub c]e[nu] transitions is presented. This study is performed at the PEP-II asymmetric B Factory, where B meson pairs are produced in the decay of the[Upsilon](4S) resonance. For the electron momentum range of 2.3-2.6 GeV/c in the[Upsilon](4S) rest frame, the partial branching ratio is measured to be[Delta][Beta](B[yields] X[sub u]e[nu])= (0.152[+-] 0.014[+-] 0.014)[center-dot] 10[sup -3].
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A preliminary determination of the first moment of the hadronic mass distributionM[sub X][sup 2] -[bar m][sub D][sup 2] in semileptonic B decays has been obtained as a function of the minimum lepton momentum, ranging from 0.9 to 1.6 GeV/c. The measurement is based on a new technique involving B[bar B] events in which one fully reconstructed B meson decays hadronically and the recoiling B decays semileptonically. The mass of the hadrons in the semileptonic decay is determined from a kinematic fit to the whole event. For different minimum lepton momenta, the mass distribution is decomposed into contributions from various charm resonant states and a non-resonant contribution, allowing for the determination of the first moment. From these moments the Heavy Quark Effective Theory (HQET) parameters[lambda][sub 1] and[bar[Lambda]] can be derived. For lepton momenta in the B rest frame above 1.5 GeV/c, we find a first moment that is compatible with existing measurements. However, if we extend the measurement to lower values of lepton momenta, the data can only be described by Operator Product Expansion calculations if we use significantly different values for[bar[Lambda]] and[lambda][sub 1] than obtained from earlier measurements based on lepton momentum spectra and the photon spectrum in b[yields] s[gamma] transitions.
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Languages : en
Pages : 19
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Charmless semileptonic decays, {bar B} 2!X{sub u}l{bar {nu}}, are studied in a sample of 232 million B{bar B} decays recorded with the BABAR detector, in events where the decay of the second B meson is fully reconstructed. Inclusive charmless decays are selected in kinematic regions where the dominant background from semileptonic B decays to charm is reduced by requirements on the hadronic mass M{sub X} and the momentum transfer q2. The partial branching fraction for {bar B} 2!X{sub u}l{bar {nu}} decays for M{sub X} 1.7 GeV/c2 and q2 8 GeV2/c4 is measured to be [Delta][Beta]({bar b} 2!X{sub u}l{bar {nu}}) = (0.87 ± 0.09{sub stat} ± 0.09{sub sys} ± 0.01{sub th}) x 10−3. The CKM matrix element.
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A largely model-independent measurement of the inclusive electron momentum spectrum and branching fraction for semileptonic decays of B mesons is presented based on data recorded at the[Upsilon](4S) resonance with the BABAR detector. Backgrounds from secondary charm decays are separated from prompt B decays using charge and angular correlations between the electron from one B meson and a high momentum electron tag from the second B meson. The resulting branching fraction is[Beta](B[yields] Xe[nu])= (10.87[+-] 0.18(stat)[+-] 0.30(syst))%. Based on this measurement we determine the CKM matrix elementV[sub cb].
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Category : Nuclear physics
Languages : en
Pages : 442
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Pages : 37
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Pages : 8
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A measurement of the first four moments of the hadronic mass distribution in B → C{sub c}l{bar [nu]} decays is presented for minimum lepton momenta varying between 0.9 and 1.6 GeV, using data recorded with the BABAR detector. Furthermore, a measurement of the inclusive electron energy spectrum for semileptonic B decays together with a measurement of its first, second and third moments for minimum electron energies between 0.6 and 1.5 GeV is reported. We determine the inclusive B → X{sub c}l{bar {nu}} branching fraction, [Beta]{sub c{ell}{nu}}, the CKM matrix element.
![Measurement of the Partial Branching Fraction for Inclusive Semileptonic B Meson Decays to Light Hadrons B-]Xu L Nu and an Improved Determination of the Quark-Mixing Matrix Element |V_ub| PDF](https://books.google.com/books/content/images/frontcover/jR1jnQAACAAJ?fife=w80-h100)
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This thesis presents an analysis of inclusive semileptonic $B \to X_u e \nu$ decays using approximately 454 million $\Upsilon(4S) \to B \bar{B}$ decays collected during the years 1999 to 2008 with the BABAR detector. The electron energy, $E_e$, and the invariant mass squared of the electron-neutrino pair, $ q^2$, are reconstructed, where the neutrino kinematics is deduced from the decay products of both B mesons. The final hadronic state, $ X_u$, consists of a sum of many hadronic channels, each of which contains at least one $u$ quark. The variables $q^2$ and $E_e$ are then combined to compute the maximum kinematically allowed invariant mass squared of the hadronic system, $s_h^{max}$. Using these kinematic quantities, the partial branching fraction, $\Delta BR(B \to X_u e \nu)$, unfolded for detector effects, is measured to be $\Delta BR(E_e>2.0 GeV, s_h^{max}3.52 GeV^2) = (3.33 \pm 0.18 \pm 0.21) \times 10^{-4} in the $\Upsilon(4S)$ and \Delta \tilde{\BR}(\tilde E_e1.9 GeV, \tilde {s}^{max}_{h}
