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$B\to Kl^+l^-$ Decay Form Factors from Three-flavor Lattice QCD.

$B\to Kl^+l^-$ Decay Form Factors from Three-flavor Lattice QCD.
Author:
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Total Pages:
Release: 2016
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ISBN:

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We compute the form factors for the B → Kl+l- semileptonic decay process in lattice QCD using gauge-field ensembles with 2+1 flavors of sea quark, generated by the MILC Collaboration. The ensembles span lattice spacings from 0.12 to 0.045 fm and have multiple sea-quark masses to help control the chiral extrapolation. The asqtad improved staggered action is used for the light valence and sea quarks, and the clover action with the Fermilab interpretation is used for the heavy b quark. We present results for the form factors f+(q2), f0(q2), and fT(q2), where q2 is the momentum transfer, together with a comprehensive examination of systematic errors. Lattice QCD determines the form factors for a limited range of q2, and we use the model-independent z expansion to cover the whole kinematically allowed range. We present our final form-factor results as coefficients of the z expansion and the correlations between them, where the errors on the coefficients include statistical and all systematic uncertainties. Lastly, we use this complete description of the form factors to test QCD predictions of the form factors at high and low q2.


B Meson Semileptonic Form Factors Using Unquenched Lattice QCD

B Meson Semileptonic Form Factors Using Unquenched Lattice QCD
Author: Emel Gulez
Publisher:
Total Pages: 116
Release: 2006
Genre: B mesons
ISBN:

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Abstract: We present state-of-the-art unquenched lattice QCD results for B meson semileptonic decay, B [rightarrow] [pi]lv, form factors. We use gauge configurations prepared by the MILC collaboration, which include the effects of the sea quarks, the s quark and two very light quarks (u and d). We employ the nonrelativistic NRQCD action to simulate the heavy b quark and a highly improved staggered quark action (AsqTad) to simulate the sea and valence light quarks. To reduce the uncertainties, we perform matching of the heavy-light current with these highly improved actions through one loop. The perturbative matching accounts for the effects of mixing with dimension 4 operators that are O(1/M) and O(a). We extrapolate the form factors f+(q2) and f0(q2) to their values at the physical pion mass using chiral perturbation theory formulas. Integrating this result, we obtain [integral] [from] 16 GeV2 [to] q2_max [d[gamma]/dq2]d2 (V_ub)2 = 1.46(35) ps−1. Combining this with a preliminary average by the Heavy Flavor Averaging Group (HFAG'05) of recent branching fraction data for exclusive B semileptonic decays from the BaBar, Belle and CLEO collaborations, leads to V_ub = 4.22(30)(51) x 10−3.


Form Factors for $B$ to $Kll$ Semileptonic Decay from Three-Flavor Lattice QCD.

Form Factors for $B$ to $Kll$ Semileptonic Decay from Three-Flavor Lattice QCD.
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Total Pages: 7
Release: 2011
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ISBN:

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We study the B 2!Kll− semileptonic decay process in three-flavor lattice QCD. We analyze several ensembles generated by theMILC collaboration at different lattice spacings and sea-quark masses. We use the asqtad improved staggered action for the light quarks and the clover action with the Fermilab interpretation for the heavy b quark. We present preliminary results for the vector current induced form factors for a range of kaon energies. Our analysis includes chiral and continuum extrapolations based on SU(2) staggered [chi]PT.


Visualization of Semileptonic Form Factors from Lattice QCD.

Visualization of Semileptonic Form Factors from Lattice QCD.
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Total Pages: 6
Release: 2009
Genre:
ISBN:

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Comparisons of lattice-QCD calculations of semileptonic form factors with experimental measurements often display two sets of points, one each for lattice QCD and experiment. Here we propose to display the output of a lattice-QCD analysis as a curve and error band. This is justified, because lattice-QCD results rely in part on fitting, both for the chiral extrapolation and to extend lattice-QCD data over the full physically allowed kinematic domain. To display an error band, correlations in the fit parameters must be taken into account. For the statistical error, the correlation comes from the fit. To illustrate how to address correlations in the systematic errors, we use the Becirevic-Kaidalov parametrization of the D → [pi]l[nu] and D → Kl[nu] form factors, and a analyticity-based fit for the B → [pi]l[nu] form factor f+.


B → K*μ+μ- and Form Factors for Semi-leptonic and Radiative B Decays

B → K*μ+μ- and Form Factors for Semi-leptonic and Radiative B Decays
Author: Aoife Katy Manek Bharucha
Publisher:
Total Pages:
Release: 2010
Genre:
ISBN:

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The hadronic environment of the LHC favours the study of exclusive modes, and of these semi-leptonic and radiative B decays will play a leading role in the search for new physics (NP). A prime example is the rare decay B?K?(? K?)?+??, where the many measurable quantities offer important new tests of the Standard Model and its extensions. We de?ne sets of CP-conserving and CP-violating observables which are studied in terms of the full form factors, calculated in QCD sum rules on the light-cone (LCSR), and QCD factorisation. Those with reduced dependence on hadronic quantities and sensitivity to NP are identi?ed. In the ?rst few years of data?taking at the LHC, the focus will be on quantities which are simple to extract while maximising the available NP sensitivity. Out of three such observables, two are well known to the experimental community. However a third, one of the CP-conserving angular observables, leads to signi?cant additional constraints on parameter space. We then study form factors for rare semi-leptonic and radiative B decays to K(?) , ? and ?s mesons, combining theoretical and phenomenological constraints from Lattice QCD, LCSR, and dispersive bounds. We pay particular attention to form factor parameterisations which are based on the so-called series expansion, and study the related systematic uncertainties on a quantitative level. Finally we calculate the leading-twist O(?s?0) corrections to the B ? ? transition form factor f+ (0) in LCSR, allowing an improved determination of the CKM matrix element |Vub |.