V. Morenas

Computing for LQCD: apeNEXT

apeNEXT is the latest in the APE collaborations series of parallel computers for computationally intensive calculations such as quantum chromo dynamics on the lattice. The authors describe the computer architectural choices that have been shaped by almost two decades of collaboration activity.

Strong Running Coupling at τ and Z 0 Mass Scales from Lattice QCD

This Letter reports on the first computation, from data obtained in lattice QCD with u, d, s, and c quarks in the sea, of the running strong coupling via the ghost-gluon coupling renormalized in the momentum-subtraction Taylor scheme. We provide readers with estimates of α(MS[over ¯])(m(τ)(2)) and α(MS[over ¯])(m(Z)(2)) in very good agreement with experimental results. Including a dynamical c quark makes the needed running of α(MS[over ¯]) safer.

High statistics determination of the strong coupling constant in Taylor scheme and its OPE Wilson coefficient from lattice QCD with a dynamical charm

We are particularly indebted to A. Le Yaouanc, J. P. Leroy, and J. Micheli for participating in many fruitful discussions at the preliminary stages of this work. We thank the support of the Spanish MICINN FPA2011-23781 research project and the IN2P3 (CNRS-Lyon), IDRIS (CNRS-Orsay), TGCC (Bruyes-Le-Chatel), and CINES (Montpellier). K. Petrov is part of the P2IO Laboratory of Excellence.

Testing QCD factorization and charming penguins in charmless B ---> PV

We try a global fit of the experimental branching ratios and CP-asymmetries of the charmless

Quantitative predictions for B semileptonic decays into D , D * , and the orbitally excited D * * in quark models in the manner of Bakamjian and Thomas

B\to PV

Semileptonic inclusive heavy meson decay: Duality in a nonrelativistic potential model in the Shifman-Voloshin limit

decays according to QCD factorisation. We find it impossible to reach a satisfactory agreement, the confidence level (CL) of the best fit is smaller than .1 %. The main reason for this failure is the difficulty to accomodate several large experimental branching ratios of the strange channels. Furthermore, experiment was not able to exclude a large direct CP asymmetry in

Lattice measurement of the Isgur-Wise functions τ1/2 and τ3/2

\bar {B^0}\to\rho^+ \pi^-

Duality in semileptonic inclusive B decays in potential models: Regular versus singular potentials

, which is predicted very small by QCD factorisation. Trying a fit with QCD factorisation complemented by a charming-penguin inspired model we reach a best fit which is not excluded by experiment (CL of about 8 %) but is not fully convincing. These negative results must be tempered by the remark that some of the experimental data used are recent and might still evolve significantly.

Uraltsev sum rule in Bakamjian-Thomas quark models

Once chosen the dynamics in one frame, the rest frame in this paper, the Bakamjian and Thomas method allows to define relativistic quark models in any frame. These models have been shown to provide, in the infinite quark mass limit, fully covariant current form factors as matrix elements of the quark current operator. In this paper we use the rest frame dynamics fitted from the meson spectrum by various authors, already shown to provide a reasonable value for

B → D∗∗ semileptonic decay in covariant quark models à la Bakamjian-Thomas

\rho^2