2,692 research outputs found

    Bs→KℓνB_s \to K \ell \nu form factors from lattice QCD

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    We report the first lattice QCD calculation of the form factors for the standard model tree-level decay Bs→KℓνB_s\to K \ell\nu. In combination with future measurement, this calculation will provide an alternative exclusive semileptonic determination of ∣Vub∣|V_{ub}|. We compare our results with previous model calculations, make predictions for differential decay rates and branching fractions, and predict the ratio of differential branching fractions between Bs→KτνB_s\to K\tau\nu and Bs→KμνB_s\to K\mu\nu. We also present standard model predictions for differential decay rate forward-backward asymmetries, polarization fractions, and calculate potentially useful ratios of Bs→KB_s\to K form factors with those of the fictitious Bs→ηsB_s\to\eta_s decay. Our lattice simulations utilize NRQCD bb and HISQ light quarks on a subset of the MILC Collaboration's 2+12+1 asqtad gauge configurations, including two lattice spacings and a range of light quark masses.Comment: 24 pages, 21 figures; Ver. 2 matches published versio

    B→Dlν form factors at nonzero recoil and extraction of |Vcb|

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    We present a lattice QCD calculation of the B→Dlν semileptonic decay form factors f+(q2) and f0(q2) for the entire physical q2 range. Nonrelativistic QCD bottom quarks and highly improved staggered quark charm and light quarks are employed together with Nf=2+1 MILC gauge configurations. A joint fit to our lattice and BABAR experimental data allows an extraction of the Cabibbo-Kobayashi-Maskawa matrix element |Vcb|. We also determine the phenomenologically interesting ratio R(D)=B(B→Dτντ)/B(B→Dlνl) (l=e,μ). We find |Vcb|B→Dexcl=0.0402(17)(13), where the first error consists of the lattice simulation errors and the experimental statistical error and the second error is the experimental systematic error. For the branching fraction ratio we find R(D)=0.300(8)

    B and Bs semileptonic decay form factors with NRQCD/HISQ quarks

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    We discuss our ongoing effort to calculate form factors for several B and Bs semileptonic decays. We have recently completed the first unquenched calculation of the form factors for the rare decay B -> K ll. Extrapolated over the full kinematic range of q^2 via model-independent z expansion, these form factor results allow us to calculate several Standard Model observables. We compare with experiment (Belle, BABAR, CDF, and LHCb) where possible and make predictions elsewhere. We discuss preliminary results for Bs -> K l nu which, when combined with anticipated experimental results, will provide an alternative exclusive determination of |Vub|. We are exploring the possibility of using ratios of form factors for this decay with those for the unphysical decay Bs -> eta_s as a means of significantly reducing form factor errors. We are also studying B -> pi l nu, form factors for which are combined with experiment in the standard exclusive determination of |Vub|. Our simulations use NRQCD heavy and HISQ light valence quarks on the MILC 2+1 dynamical asqtad configurations.Comment: 7 pages, 5 figures, presented at the 31st International Symposium on Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, German

    Bs→DsℓνB_s \to D_s \ell \nu Form Factors and the Fragmentation Fraction Ratio fs/fdf_s/f_d

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    We present a lattice quantum chromodynamics determination of the scalar and vector form factors for the Bs→DsℓνB_s \rightarrow D_s \ell \nu decay over the full physical range of momentum transfer. In conjunction with future experimental data, our results will provide a new method to extract ∣Vcb∣|V_{cb}|, which may elucidate the current tension between exclusive and inclusive determinations of this parameter. Combining the form factor results at non-zero recoil with recent HPQCD results for the B→DℓνB \rightarrow D \ell \nu form factors, we determine the ratios f0Bs→Ds(Mπ2)/f0B→D(MK2)=1.000(62)f^{B_s \rightarrow D_s}_0(M_\pi^2) / f^{B \rightarrow D}_0(M_K^2) = 1.000(62) and f0Bs→Ds(Mπ2)/f0B→D(Mπ2)=1.006(62)f^{B_s \rightarrow D_s}_0(M_\pi^2) / f^{B \rightarrow D}_0(M_\pi^2) = 1.006(62). These results give the fragmentation fraction ratios fs/fd=0.310(30)stat.(21)syst.(6)theor.(38)latt.f_s/f_d = 0.310(30)_{\mathrm{stat.}}(21)_{\mathrm{syst.}}(6)_{\mathrm{theor.}}(38)_{\mathrm{latt.}} and fs/fd=0.307(16)stat.(21)syst.(23)theor.(44)latt.f_s/f_d = 0.307(16)_{\mathrm{stat.}}(21)_{\mathrm{syst.}}(23)_{\mathrm{theor.}}(44)_{\mathrm{latt.}}, respectively. The fragmentation fraction ratio is an important ingredient in experimental determinations of BsB_s meson branching fractions at hadron colliders, in particular for the rare decay B(Bs→μ+μ−){\cal B}(B_s \rightarrow \mu^+ \mu^-). In addition to the form factor results, we make the first prediction of the branching fraction ratio R(Ds)=B(Bs→Dsτν)/B(Bs→Dsℓν)=0.301(6)R(D_s) = {\cal B}(B_s\to D_s\tau\nu)/{\cal B}(B_s\to D_s\ell\nu) = 0.301(6), where ℓ\ell is an electron or muon. Current experimental measurements of the corresponding ratio for the semileptonic decays of BB mesons disagree with Standard Model expectations at the level of nearly four standard deviations. Future experimental measurements of R(Ds)R(D_s) may help understand this discrepancy.Comment: 21 pages, 15 figure

    Contours and Contouring in Hydrography Part II - Interpolation

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    In Part I of this series, the authors discussed those issues which we feel are fundamentally important and which must be addressed by any method which aims to mechanize the drawing of depth contours for hydrographic charts. In this article we begin the discussion of the How of contouring. In particular, we concentrate on some of the most common methods used in the interpolation of the synthetic surface upon which computed contours will lie
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