0000000000682132
AUTHOR
J. M. Flynn
Vertical bar V(ub)vertical bar from exclusive semileptonic B -> rho decays
We use Omnes representations of the form factors V, A(1) and A(2) for exclusive semileptonic B -> rho decays, and apply them to combine experimental partial branching fraction information with theoretical calculations of the three form factors to extract vertical bar V-ub vertical bar. We find vertical bar V-ub vertical bar = (2.8 +/- 0.2(stat)+/- 0.5(sys)) x 10(-3). where we have conservatively assumed a 20% systematic error to account for the use of the quenched approximation in the lattice QCD calculations of the form factors. This value of vertical bar V-ub vertical bar is slightly lower than the values extracted from exclusive semileptonic B -> pi decays, (3.47 +/- 0.29 +/- 0.03) x 10(…
Form factors for semileptonic B -> pi and D -> pi decays from the Omnes representation
We use the Omnes representation to obtain the q-squared dependence of the form factors f+ and f0 for semileptonic H -> pi decays from the elastic pi H -> pi H scattering amplitudes, where H denotes a B or D meson. The scattering amplitudes used satisfy elastic unitarity and are calculated from two-particle irreducible amplitudes obtained using tree-level heavy meson chiral perturbation theory (HMChPT). The q-squared dependences for the form factors agree with lattice QCD results when the HMChPT coupling constant, g, takes values smaller than 0.32, and confirm the milder dependence of f0 on q-squared found in sumrule calculations.
A nonrelativistic quark model evaluation of exclusive $b\to c$ semileptonic decay of triply heavy baryons and $c\to s,d$ semileptonic decay of $cb$ baryons
We present results for exclusive $b\to c$ semileptonic decays of ground state triply-heavy baryons and for semileptonic $c\to s,d$ decays of doubly heavy ground state $cb$ baryons. In both cases, we have derived for the first time heavy quark spin symmetry relations for the hadronic amplitudes near zero recoil. Though strictly valid in the limit of very large heavy quark masses and near zero recoil, they turn out to be reasonable accurate for the whole available phase space in these decays and for the actual heavy quark masses we use. With these relations we have made approximate, but model independent, predictions for ratios of decay widths. In the case of spin-1/2 $cb$ baryons, we find th…
Kl3 and pion form factors using partially twisted boundary conditions
We compute the Kl3 and pion form factors using partially twisted boundary conditions. The twists are chosen so that the Kl3 form factors are calculated directly at zero momentum transfer (q^2=0), removing the need for a q^2 interpolation, while the pion form factor is determined at values of q^2 close to q^2=0. The simulations are performed on an ensemble of the RBC/UKQCD collaboration's gauge configurations with Domain Wall Fermions and the Iwaski gauge action with an inverse lattice spacing of 1.73(3) GeV. Simulating at a single pion mass of 330 MeV, we find the pion charge radius to be _{330 MeV}=0.354(31) fm^2 which, using NLO SU(2) chiral perturbation theory, translates to a value of =…