7 research outputs found
Towards a lattice determination of the coupling
The coupling is related to the form factor at zero
momentum of the axial current between - and -states. This form
factor is evaluated on the lattice using static heavy quarks and light quark
propagators determined by a stochastic inversion of the fermionic bilinear. The
\gBBP coupling is related to the coupling between heavy mesons and
low-momentum pions in the effective heavy meson chiral lagrangian. The coupling
of the effective theory can therefore be computed by numerical simulations. We
find the value . Besides its theoretical interest, the
phenomenological implications of such a determination are discussed.Comment: 20 pages, 6 figure
Sea quark effects in B_K from N_f=2 clover-improved Wilson fermions
We report calculations of the parameter B_K appearing in the Delta S=2
neutral kaon mixing matrix element, whose uncertainty limits the power of
unitarity triangle constraints for testing the standard model or looking for
new physics. We use two flavours of dynamical clover-improved Wilson lattice
fermions and look for dependence on the dynamical quark mass at fixed lattice
spacing. We see some evidence for dynamical quark effects and in particular B_K
decreases as the sea quark masses are reduced towards the up/down quark mass.Comment: 17 pages, 4 figures, uses JHEP3.cls, added comments and reference
Lifetimes of b-flavoured hadrons
I discuss the heavy quark expansion for the inclusive widths of heavy-light
hadrons, which predicts quite well the experimental ratios of B_q meson
lifetimes. As for , current determinations of
contribution to do not allow to explain the small measured
value of . As a final topic, I discuss the
implications of the measurement of the B_c lifetime.Comment: LaTex, 4 pages, 1 figure. Talk given at the "U.K. Phenomenology
Workshop on Heavy Flavours and CP violation" Durham, 17-22 Sep. 2000 (Mixing
and Lifetimes Working Group
Quenched charmonium spectrum
We study charmonium using the standard relativistic formalism in the quenched
approximation, on a set of lattices with isotropic lattice spacings ranging
from 0.1 to 0.04 fm. We concentrate on the calculation of the hyperfine
splitting between eta_c and J/psi, aiming for a controlled continuum
extrapolation of this quantity. The splitting extracted from the
non-perturbatively improved clover Dirac operator shows very little dependence
on the lattice spacing for fm. The dependence is much stronger for
Wilson and tree-level improved clover operators, but they still yield
consistent extrapolations if sufficiently fine lattices, fm (), are used. Our result for the hyperfine splitting is
77(2)(6) MeV (where Sommer's parameter, r_0, is used to fix the scale). This
value remains about 30% below experiment. Dynamical fermions and OZI-forbidden
diagrams both contribute to the remainder. Results for the eta_c and J/psi wave
functions are also presented.Comment: 22 pages, 7 figure
Spectroscopy of doubly-charmed baryons in lattice QCD
We present results for masses of spin-1/2 and spin-3/2 double-charm baryons in quenched lattice QCD, from an exploratory study using a non-perturbatively improved clover action at ?=6.2. We have studied local operators and we observe, after appropriate projections, a good signal for the ground states. We also present results for single-charmed baryons and spin-splittings for both double- and single-charmed states