246 research outputs found

    QCD-Factorization of inclusive B decays and |Vub|

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    Recent progress in the theoretical description of inclusive B to X_u l nu decays in the shape-function region is reported. Finite moments of the shape function are related to HQET parameters. Event fractions for several experimental cuts are presented, with a particular emphasis on the hadronic variable P+. The aim of this talk is to introduce the P+ spectrum, to compare it to the hadronic invariant mass spectrum and the charged-lepton energy spectrum, and to study the prospect of evaluating |Vub| in the presence of a large background from B to X_c decays.Comment: 8 pages, 7 figures, uses espcrc2.sty (included). Talk presented at the Sixth International Conference on Hyperons, Charm and Beauty Hadrons, IIT, Chicago, June 27--July 3 200

    A two-loop relation between inclusive radiative and semileptonic B-decay spectra

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    A shape-function independent relation is derived between the partial B->X_u+l+nu decay rate with a cut on P_+=E_X-P_X<Delta and a weighted integral over the normalized B->X_s+gamma photon-energy spectrum. The leading-power contribution to the weight function is calculated at next-to-next-to-leading order in renormalization-group improved perturbation theory, including exact two-loop matching corrections at the scale mu_i^2 ~ m_b*Lambda_{QCD}. The overall normalization of the weight function is obtained up to yet unknown corrections of order [alpha_s(m_b)]^2. Power corrections from phase-space factors are included exactly, while the remaining subleading contributions are included at first order in 1/m_b. At this level unavoidable hadronic uncertainties enter, which are estimated in a conservative way. The combined theoretical accuracy in the extraction of |V_{ub}| is at the level of 5% if a value of Delta near the charm threshold can be achieved experimentally.Comment: 22 pages, 4 figures; few comments and one reference added; version to appear in JHE

    Proposal for a Precision Measurement of |Vub|

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    A new method for a precision measurement of the CKM matrix element |Vub| is discussed, which combines good theoretical control with high efficiency and a powerful discrimination against charm background. The resulting combined theoretical uncertainty on |Vub| is estimated to be 10%.Comment: 4 pages, 2 figures, RevTe

    Factorization and the Soft Overlap Contribution to Heavy-to-Light Form Factors

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    Using the formalism of soft-collinear effective theory, a complete separation of short- and long-distance contributions to heavy-to-light transition form factors at large recoil is performed. The universal functions ζM(E)\zeta_M(E) parameterizing the ``soft overlap'' contribution to the form factors are defined in terms of matrix elements in the effective theory. Endpoint configurations corresponding to kinematic situations where one of the valence partons in the external mesons carries very small momentum are accounted for in terms of operators involving soft-collinear messenger fields. They contribute at leading order in ΛQCD/E\Lambda_{\rm QCD}/E and spoil factorization. An analysis of operator mixing and renormalization-group evolution in the effective theory reveals that the intermediate scale EΛ\sqrt{E\Lambda} is without significance to the soft functions ζM(E)\zeta_M(E), and that the soft overlap contribution does not receive a significant perturbative (Sudakov) suppression.Comment: 30 pages, 6 figures. Erratum adde

    Quality-control procedures for ship-board biogeochemical time series data

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    Framework of the envisioned time-series synthesis product used to indicate the consistency of biogeochemical time-series data (in-)between different ship-based sites
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