D meson semileptonic form factors in Nf=3 QCD with M\"obius domain-wall quarks

We present our calculation of D \to pi and D \to K semileptonic form factors in Nf = 2+1 lattice QCD. We simulate three lattice cutoffs 1/a \sim 2.5, 3.6 and 4.5 GeV with pion masses as low as 230 MeV. The M\"obius domain-wall action is employed for both light and charm quarks. We present our results for the vector and scalar form factors and discuss their dependence on the lattice spacing, light quark masses and momentum transfer.Comment: 8 pages, 5 figures, talk presented at the 35th International Symposium on Lattice Field Theory (Lattice 2017), 18-24 June 2017, Granada, Spai

Semileptonic BcB_c decays from full lattice QCD

We present first lattice QCD results for semileptonic form factors for the decays $B_c \to \eta_c l \nu$ and $B_c \to J/\psi l \nu$ over the full $q^2$ range, using both improved non-relativistic QCD (NRQCD) and fully relativistic (HISQ) formalisms. These can be viewed as prototype calculations for pseudoscalar to pseudoscalar and pseudoscalar to vector decays involving a $b \to c$ transition. In particular we can use information from the relativistic computations to fix the NRQCD current normalisations, which can then be used in improved computations of decays such as $B \to D l \nu$ and $B \to D^* l \nu$.Comment: 3 pages, 3 figures. Poster presented at the 16th International Conference on B-Physics at Frontier Machines, 2-6 May 2016, Marseille, Franc

The B(s)→D(s)lνB_{(s)} \to D_{(s)}l\nu Decay with Highly Improved Staggered Quarks and NRQCD

We report on progress of a lattice QCD calculation of the $B\to Dl\nu$ and $B_s\to D_s l\nu$ semileptonic form factors. We use a relativistic staggered action (HISQ) for light and charm quarks, and an improved non-relativistic (NRQCD) action for bottom, on the second generation MILC ensembles.Comment: Presented at Lattice 2017, the 35th International Symposium on Lattice Field Theory at Granada, Spain (18-24 June 2017

Bottomonium and B physics with lattice NRQCD b quarks

Lattice Nonrelativistic QCD (NRQCD) is a formalism that allows $b$ quarks to be simulated in their bound states in lattice QCD. It requires only a relatively straightforward evolution equation and is therefore much faster than other lattice QCD formalisms. We perform calculations using radially improved NRQCD for mesons that contain $b$ quarks on gluon field configurations generated by the MILC collaboration with $2+1+1$ flavours of sea quarks, and including light quarks down to their physical masses. We calculate properties of bottomonium mesons; in particular, the $\Upsilon$ and $\eta_b$. The kinetic mass of these states over a range of momenta is calculated and shown to be stable. We determine the $\Upsilon$ and $\Upsilon^{\prime}$ leptonic widths for the first time in lattice QCD after determining a renormalisation factor matching NRQCD to QCD using temporal moments of the meson correlators. We also compare these temporal moments to continuum temporal moments derived from $q^2$-derivative moments of the $b$ quark polarisation function in continuum QCD perturbation theory. Finally, we use the NRQCD moments to determine the mass of the $b$ quark and the contribution of a $b$ quark loop to the hadronic piece of the muon anomalous magnetic moment. The same NRQCD action can be used to simulate the $b$ quark in heavy-light mesons. We present results here for the form factor $f_0{(q^2_{\mathrm{max}})}$ of the semileptonic $B\rightarrow \pi \ell \nu$ decay. We show that the soft pion theorem, which states that $f_0{(q^2_{\mathrm{max}})}=f_B/f_{\pi}$ in the chiral limit, holds. This was uncertain previously as simulations were carried out with light quarks that were much heavier than their physical masses. The lattice gluon field configurations with physical light quarks allow us to overcome this issue and simulate at the physical pion mass. Finally, we briefly discuss the decays $B_s \rightarrow K \ell \nu$ and the fictitious $B_s \rightarrow \eta_s$ decay. These processes again utilise NRQCD $b$ quarks

Form factors of B→πℓνB\to\pi\ell\nu and a determination of ∣Vub∣|V_{ub}| with M\"{o}bius domain-wall-fermions

Using a fully relativistic lattice fermion action, we compute the form factors of the semileptonic decay $B\to\pi\ell\nu$, which is required for the determination of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{ub}|$. We employ the M\"{o}bius domain-wall fermion formalism for the generation of lattice ensembles with 2+1 sea quark flavours as well as for the valence heavy and light quarks. We compute the form factors at various values of the lattice spacing and multiple light and heavy quark masses, and extrapolate the results to the physical point. We combine our lattice results with the available experimental data to obtain $|V_{ub}| = (3.93\pm 0.41)\times 10^{-3}$.Comment: 33 pages, 20 figures, 12 tables. Plus supplementary material: 20 pages, 7 figures, 8 table