Heavy Quark Phenomenology from Lattice QCD

Recent results relevant for the B-physics phenomenology, obtained from lattice QCD simulations by the APE Collaboration, are reviewed. This includes the B0-B0bar mixing amplitude, B-> pi semileptonic decay and the relative width difference of B0_s mesons, $(\Delta \Gamma/\Gamma)_{B_s}$.Comment: 4 page

Theoretical progress in describing the B-meson lifetimes

The present status of the theoretical estimates of the difference between the widths of the neutral Bs-mesons and of the B-meson lifetime ratios is reviewed. In particular, the lattice results for the matrix elements of the relevant (delta B=2)-operators are updated and the first lattice QCD results for the matrix elements of (delta B=0)-operators are presented. In both cases, the NLO perturbative QCD corrections in the coefficient functions have been included. The theoretically updated results are: (delta Gamma/Gamma)_{Bs} = (7 +/- 4) %, tau(B+)/tau(Bd) = 1.07(3) and tau(Bs)/tau(Bd) = 1.00(2).Comment: 14 pages (5 figures), Extended version of the talk given at IEC-HEP Budapest, 200

A model to accommodate the BB-physics anomalies

After briefly reviewing the status of the $B$-physics anomalies, describing the challenges of building a scenario of physics beyond the Standard Model that can accommodate the observed departures from lepton flavor universality, I discuss a new model, based on extending the Standard Model by two light [$\mathcal{O}(1\,\mathrm{TeV})$] scalar leptoquarks. That model, in addition to satisfying a number of flavor physics constraints both at low and high energies, also allows for a $SU(5)$ unification.Comment: 8 pages writeup, talk given at the 53rd Rencontres de Moriond EW201

g(B*Bpi)-coupling in the static heavy quark limit

By means of QCD simulations on the lattice, we compute the coupling of the heavy-light mesons to a soft pion in the static heavy quark limit. The gauge field configurations used in this calculations include the effect of N_f=2 dynamical Wilson quarks, while for the static quark propagator we use its improved form (so called HYP). On the basis of our results we obtain that the coupling g=0.44 +/- 0.03 (+0.07/-0.00), where the second error is flat (not gaussian).Comment: 7 pages, 3 figs (published version

Radiative decays of charmonia on the lattice

We present the results of our lattice QCD study of the hadronic matrix elements relevant to the physical radiative J/psi -> eta_c gamma and hc -> eta_c gamma decays. From computations with Nf=2 dynamical quark in twisted mass QCD at four lattice spacings, we were able to take the continuum limit and obtained Gamma(J/psi -> eta_c gamma) = 2.64(11) keV and Gamma(hc -> eta_c gamma) = 0.72(5) MeV. We also computed the the hyperfine splitting and found that it does not depend from the sea quark mass and we obtain Delta = m_J/psi - m_eta_c = 112(4) MeV.Comment: 8 pages, 4 figures. Proceedings of the "Xth Quark Confinement and the Hadron Spectrum", 8-12 October 2012, TUM Campus Garching, Munich, German

Parametrisations of the D -> K l nu form factor and the determination of \hat{g}

The vector form factor f_+(t) of the semileptonic decay D -> K l nu, measured recently with a high accuracy, can be used to determine the strong coupling constant g_{D_s^* D K}. The latter is related to the normalised coupling \hat{g} releveant in heavy-meson chiral perturbation theory. This determination relies on the estimation of the residue of the form factor at the D_s^* pole and thus on an extrapolation of the form factor in the unphysical region (m_D-m_K)^2<t<(m_D+m_K)^2. We test this extrapolation for several parametrisations of the form factors by determining the value of \hat{g}, whose value can be compared to other (experimental and theoretical) estimates. Several unsophisticated parametrisations, differing by the amount of physical information that they embed, are shown to pass this test. An apparently more elaborated parametrisation of form factors, the so-called z-expansion, is at variance with the other models, and we point out some significant shortcomings of this parametrisation for the problem under consideration.Comment: 16 pages, 2 figures. A few references added. Accepted for publication in JoP

Operator product expansion and quark condensate from Lattice QCD in coordinate space

We present a Lattice QCD determination of the chiral quark condensate based on a new method. We extract the quark condensate from the operator product expansion of the quark propagator at short euclidean distances, where it represents the leading contribution in the chiral limit. From this study we obtain ^ms(2 GeV)=-(265+-5+-22 MeV)^3$, in good agreement with determinations of this quantity based on different approaches. The simulation is performed by using the O(a)-improved Wilson action at beta=6.45 on a volume 32^3\times70 in the quenched approximation

BK from the lattice with Wilson quarks

We report our results for the bag-parameter BK obtained from the quenched simulations on the lattice with Wilson fermions at three values of the lattice spacing. We implemented the method by which no subtraction of the mixing with other four-fermion dS=2 operators is needed. Our final result, in terms of the renormalisation group invariant bag-parameter, is BK = 0.96 +/- 0.10.Comment: 12 pages, 3 figures [version published in Eur.Phys.J.C