17 research outputs found
Form Factors for B -> pi l nu-bar_l and B -> K* gamma Decays on the Lattice
We present a unified method for analysing form factors in B -> pi l nu-bar_l
and B -> K* gamma decays. The analysis provides consistency checks on the q^2
and 1/M extrapolations necessary to obtain the physical decay rates. For the
first time the q^2 dependence of the form factors is obtained at the B scale.
In the B -> pi l nu-bar_l case, we show that pole fits to f^+ may not be
consistent with the q^2 behaviour of f^0, leading to a possible factor of two
uncertainty in the decay rate and hence in the value of |V_{ub}|^2 deduced from
it. For B -> K* gamma, from the combined analysis of form factors T_1 and T_2,
we find the hadronisation ratio R_{K^*} of the exclusive B -> K* gamma to the
inclusive b -> s gamma rates is of order 35% or 15% for constant and pole-type
behaviour of T_2 respectively.Comment: 13 pages, uuencoded compressed postscript file (including five
figures). Also available from
http://wwwhep.phys.soton.ac.uk/hepwww/papers/shep9509
Gauge Theories on a 2+2 Anisotropic Lattice
The implementation of gauge theories on a four-dimensional anisotropic
lattice with two distinct lattice spacings is discussed, with special attention
to the case where two axes are finely and two axes are coarsely discretized.
Feynman rules for the Wilson gauge action are derived and the renormalizability
of the theory and the recovery of the continuum limit are analyzed. The
calculation of the gluon propagator and the restoration of Lorentz invariance
in on-shell states is presented to one-loop order in lattice perturbation
theory for on both 2+2 and 3+1 lattices.Comment: 27 pages, uses feynmf. Font compatibility adjuste
The semileptonic B->pi decay in a Constituent Quark-Meson model
We evaluate the form factors describing the exclusive decay B-> pi l nu by
using a Constituent Quark-Meson model based on an effective quark-meson
Lagrangian (CQM). The model allows for an expansion in the pion momenta and we
consider terms up to the first order in the pion field derivatives. We compute
the leading terms in the soft pion limit and consider corrections to this
limit.Comment: 6 pages, 3 figures, LaTeX (uses aps, epsf, revtex), formula 26
corrected, discussion enlarged, references updated and other minor change
Strong Couplings of Heavy Mesons to A Light Vector Meson in QCD
We make a detailed analysis of the and
strong couplings and
using QCD light cone sum rules(LCSR). The
existing some negligence is pointed out in the previous LCSR calculation on
) and an updated estimate is presented. Our
findings can be used to understand the behavior of the
semileptonic form factors at large momentum transitions.Comment: 15 pages, latex, 2 figures, version appearing in PRD, typos correcte
Charming penguins in B => K* pi, K (rho,omega,phi) decays
We evaluate the decays B => K* pi, K (rho,omega,phi) adding the long distance
charming penguin contributions to the short distance: Tree+Penguin amplitudes.
We estimate the imaginary part of the charming penguin by an effective field
theory inspired by the Heavy Quark Effective Theory and parameterize its real
part. The final results for branching ratios depend on only two real parameters
and show a significant role of the charming penguins. The overall agreement
with the available experimental data is satisfactory.Comment: 13 pages, 1 figur
The transition form factors for semi-leptonic weak decays of in QCD sum rules
Within the Standard Model, we investigate the semi-leptonic weak decays of
. The various form factors of transiting to a single charmed
meson () are studied in the framework of the QCD sum rules.
These form factors fully determine the rates of the weak semi-leptonic decays
of and provide valuable information about the non-perturbative QCD
effects. Our results indicate that the decay rate of the semi-leptonic weak
decay mode is at order of .Comment: 28 pages, 6 figures, revised version to be published in Eur.Phys.J.
Hadronic physics in lattice QCD
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