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We present the first unquenched lattice-QCD calculation of the hadronic form factors for the exclusive decay $overline{B} rightarrow D ell overline{ u}$ at nonzero recoil. We carry out numerical simulations on fourteen ensembles of gauge-field configurations generated with 2+1 flavors of asqtad-improved staggered sea quarks. The ensembles encompass a wide range of lattice spacings (approximately 0.045 to 0.12 fm) and ratios of light (up and down) to strange sea-quark masses ranging from 0.05 to 0.4. For the $b$ and $c$ valence quarks we use improved Wilson fermions with the Fermilab interpretation, while for the light valence quarks we use asqtad-improved staggered fermions. We extrapolate our results to the physical point using rooted staggered heavy-light meson chiral perturbation theory. We then parameterize the form factors and extend them to the full kinematic range using model-independent functions based on analyticity and unitarity. We present our final results for $f_+(q^2)$ and $f_0(q^2)$, including statistical and systematic errors, as coefficients of a series in the variable $z$ and the covariance matrix between these coefficients. We then fit the lattice form-factor data jointly with the experimentally measured differential decay rate from BaBar to determine the CKM matrix element, $|V_{cb}|=(39.6 pm 1.7_{rm QCD+exp} pm 0.2_{rm QED})times 10^{-3}$. As a byproduct of the joint fit we obtain the form factors with improved precision at large recoil. Finally, we use them to update our calculation of the ratio $R(D)$ in the Standard Model, which yields $R(D) = 0.299(11)$.
We present the first unquenched lattice-QCD calculation of the form factors for the decay $Bto D^astell u$ at nonzero recoil. Our analysis includes 15 MILC ensembles with $N_f = 2+1$ flavors of asqtad sea quarks, with a strange quark mass close to it
I discuss recent progress in lattice calculations of $B to D^{(*)} ell u$ form factors, important for the precision determination of $|V_{cb}|$ in the Standard Model (SM), and for testing SM expectations of lepton flavor universality in observables
We calculate the $B topiell u$ and $B_s to K ell u$ form factors in dynamical lattice QCD. We use the (2+1)-flavor RBC-UKQCD gauge-field ensembles generated with the domain-wall fermion and Iwasaki gauge actions. For the $b$ quarks we use the anisotr
We report on our calculation of the B to D^(*) ell u form factors in 2+1 flavor lattice QCD. The Mobius domain-wall action is employed for light, strange, charm and bottom quarks. At lattice cutoffs 1/a sim 2.4, 3.6 and 4.5 GeV, we simulate bottom q
We report on our study of the B to D^(*) ell u semileptonic decays at zero and nonzero recoils in 2+1 flavor QCD. The Mobius domain-wall action is employed for light, charm and bottom quarks at lattice cutoffs 1/a = 2.5 and 3.6 GeV. We take bottom q