Form factors for B to Kll semileptonic decay from three-flavor lattice QCD (original) (raw)
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Physical Review D, 2009
We calculate the form factor f + (q 2 ) for B-meson semileptonic decay in unquenched lattice QCD with 2+1 flavors of light sea quarks. We use Asqtad-improved staggered light quarks and a Fermilab bottom quark on gauge configurations generated by the MILC Collaboration. We simulate with several light quark masses and at two lattice spacings, and extrapolate to the physical quark mass and continuum limit using heavy-light meson staggered chiral perturbation theory. We then fit the lattice result for f + (q 2 ) simultaneously with that measured by the BABAR experiment using a parameterization of the form factor shape in q 2 which relies only on analyticity and unitarity in order to determine the CKM matrix element |V ub |. This approach reduces the total uncertainty in |V ub | by combining the lattice and experimental information in an optimal, model-independent manner. We find a value of |V ub | × 10 3 = 3.38 ± 0.35.
Form factors for semi-leptonic B decays
We report on form factors for the B->K l^+ l^- semi-leptonic decay process. We use several lattice spacings from a=0.12 fm down to 0.06 fm and a variety of dynamical quark masses with 2+1 flavors of asqtad quarks provided by the MILC Collaboration. These ensembles allow good control of the chiral and continuum extrapolations. The b-quark is treated as a clover quark with the Fermilab interpretation. We update our results for f_\parallel and f_\perp, or, equivalently, f_+ and f_0. In addition, we present new results for the tensor form factor f_T. Model independent results are obtained based upon the z-expansion.
Semileptonic B to Tensor Meson Decays in Standard Model with Fourth Generation
Arxiv preprint arXiv:1103.3934, 2011
The B → K * 2 (1430)l + l − (l = µ, τ ) decays are analyzed in the Standard Model extended to fourth generation of quarks (SM4). The decay rate, forward-backward asymmetry, lepton polarization asymmetries and the helicity fractions of the final state K * 2 (1430) meson are obtained using the form factors calculated in the light cone sum rules (LCSR) approach. We have utilized the constraints on different fourth generation parameters obtained from the experimental information on K, B and D decays and from the electroweak precision data to explore their impact on the B → K * 2 (1430)l + l − decay. We find that the values of above mentioned physical observables deviate deviate significantly from their minimal SM predications. We also identify a number of correlations between various observables in B → K * 2 (1430)l + l − and B → K * (892)l + l − decays. Therefore a combined analysis of these two decays will compliment each other in the searches of SM4 effects in flavor physics. * Electronic address: mjunaid@ncp.edu.pk † Electronic address: jamil@ncp.edu.pk 1 arXiv:1103.3934v3 [hep-ph] 30 Sep 2011
Lattice study of semileptonic B decays: B¯→Dlν¯ decays
Physical Review D, 1995
We present a study of semi-leptonicB → Dℓν decays in quenched lattice QCD through a calculation of the matrix element D|cγ µ b|B on a 24 3 × 48 lattice at β = 6.2, using an O (a)-improved fermion action. We perform the calculation for several values of the initial and final heavy-quark masses around the charm mass, and three values of the light-(anti)quark mass around the strange mass. Because the charm quark has a bare mass which is almost 1/3 the inverse lattice spacing, we study the ensuing mass-dependent discretization errors, and propose a procedure for subtracting at least some of them non-perturbatively.
An estimate of the B--> K* gamma form factor
2006
We present the results of a lattice QCD calculation of the form factor relevant to B → K * γ decay. Our final value, T (0) = 0.24 ± 0.03 +0.04 −0.01 , is obtained in the quenched approximation, and by extrapolating M 3/2 H × T H→K * (q 2 = 0) from the directly accessed H-heavy mesons to the meson B. We also show that the extrapolation from B → K * γ * (q 2 = 0) to B → K * γ (q 2 = 0), leads to a result consistent with the one quoted above. On the other hand, our results are not accurate enough to solve the SU (3) flavor breaking effects in the form factor and we quote T B→K * (0)/T B→ρ (0) = 1.2(1), as our best estimate.
Form factorA0(q2), nonleptonicD(B)→PVtransitions, and rareB→K*γ decays
Physical Review D, 1995
We use three-point function QCD sum rules to calculate the form factor A 0 (q 2) appearing in the matrix element of the flavour-changing axial current between the D(B) state and a vector meson state. We describe the role of this form factor in nonleptonic D(B) → P V decays and analyze the light SU (3) F symmetry breaking effects. We also discuss a proposal to relate the branching ratio of B → K * γ to the spectrum of the semileptonic B → ρℓν decay.
A proposal for B physics on current lattices
Journal of High Energy Physics, 2010
A method to extract B-physics parameters (b-quark mass and f B , $ {f_{{B_s}}} $ decay constants) from currently available lattice data is presented and tested. The approach is based on the idea of constructing appropriate ratios of heavy-light meson masses and decay constants, respectively, possessing a precisely known static limit, and evaluating them at various pairs of heavy quark masses around the charm. Via a smooth interpolation in the heavy quark mass from the easily accessible charm region to the asymptotic point, B-physics parameters are computed with a few percent (statistical + systematic) error using recently produced N f = 2 maximally twisted Wilson fermions data.
$B\to\pi$ semileptonic form factors from unquenched lattice QCD
Proceedings of The 32nd International Symposium on Lattice Field Theory — PoS(LATTICE2014)
We compute the B → π ν semileptonic form factors and update the determination of the CKM matrix element |V ub |. We use the MILC asqtad ensembles with N f = 2 + 1 sea quarks at four different lattice spacings in the range a ≈ 0.045 fm to 0.12 fm. The lattice form factors are extrapolated to the continuum limit using SU(2) staggered chiral perturbation theory in the hard pion limit, followed by an extrapolation in q 2 to the full kinematic range using a functional zparameterization. The extrapolation is combined with the experimental measurements of the partial branching fraction to extract |V ub |. Our preliminary result is |V ub | = (3.72 ± 0.14) × 10 −3 , where the error reflects both the lattice and experimental uncertainties, which are now on par with each other.