434 research outputs found
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
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
Quark Masses and Renormalization Constants from Quark Propagator and 3-point Functions
We have computed the light and strange quark masses and the renormalization
constants of the quark bilinear operators, by studying the large-p^2 behaviour
of the lattice quark propagator and 3-point functions. The calculation is
non-perturbatively improved, at O(a), in the chiral limit. The method used to
compute the quark masses has never been applied so far, and it does not require
an explicit determination of the quark mass renormalization constant.Comment: LATTICE99 (Improvement and Renormalization) - 3 pages, 2 figure
Decays of Heavy Mesons
We present preliminary results for heavy to light transitions of pseudoscalar
mesons, induced by the vector and tensor operators. This lattice study is
performed in quenched approximation, by using the nonperturbatively improved
Wilson action and operators. We also update the values of the heavy-light meson
decay constants.Comment: LATT99(Heavy Quarks), 3 pages, 2 figure
Perturbative renormalization for static and domain-wall bilinears and four-fermion operators with improved gauge actions
We calculate one-loop renormalization factors for heavy-light bilinears as
well as four-fermion operators relevant for mixing
calculations on the lattice. We use the static approximation for heavy quarks
and the domain-wall formulation for light quarks. We present results for
different choices of improved gauge action.Comment: 21 pages, 3 figures, 3 tables, revtex
Lattice calculation of SU(3) flavor breaking ratios in B - anti-B mixing
We present an unquenched lattice calculation for the SU(3) flavor breaking
ratios of the heavy-light decay constants and the matrix
elements. The calculation was performed on lattices with two
dynamical flavors of domain-wall quarks and inverse lattice spacing GeV. Heavy quarks were implemented using an improved lattice
formulation of the static approximation. In the infinite heavy-quark mass limit
we obtain , , where the first error is statistical and the second systematic.Comment: 23 pages, 8 figures, RevTeX4; mentioned existence of 1/m_b
corrections, minor changes improving readabilit
Heavy --> Light semileptonic decays of pseudoscalar mesons from lattice QCD
We have computed the form factors for B --> pi and D --> K(pi) semileptonic
decays on the lattice by using full non-perturbative O(a) improvement, in the
quenched approximation. Our results are expressed in terms of few parameters
which describe the q^2-dependence and normalization of the form factors.Comment: 28 pages (LaTeX2e), 11 PostScript figures (version to appear in
Nucl.Phys.B
B-parameters of the complete set of matrix elements of (Delta B = 2) operators from the lattice
We compute on the lattice the ``bag'' parameters of the five (Delta B = 2)
operators of the supersymmetric basis, by combining their values determined in
full QCD and in the static limit of HQET. The extrapolation of the QCD results
from the accessible heavy-light meson masses to the B-meson mass is constrained
by the static result. The matching of the corresponding results in HQET and in
QCD is for the first time made at NLO accuracy in the MSbar(NDR)
renormalization scheme. All results are obtained in the quenched approximation.Comment: 27 pages (5 figures
Matrix elements of the complete set of \Delta B = 2 and \Delta C = 2 operators in heavy meson chiral perturbation theory
Using heavy meson chiral perturbation theory, we consider the light
quark-mass and spatial volume dependence of the matrix elements of \Delta B=2
and \Delta C=2 four-quark operators relevant for
B^{0}_{(s)}{-}\bar{B}^{0}_{(s)} and D^{0}{-}\bar{D}^{0} mixing, and the B_{s}
meson width difference. Our results for these matrix elements are obtained in
the N_{f}=2+1 partially quenched theory, which becomes full QCD in the limit
where sea and valence quark masses become equal. They can be used in
extrapolation of lattice calculations of these matrix elements to the physical
light quark masses and to infinite volume. An important conclusion of this
paper is that the chiral extrapolations for matrix elements of heavy-light
meson mixing beyond the Standard Model, and those relevant for the B_s width
difference are more complicated than that for the Standard Model mixing matrix
elements.Comment: 13 pages; version accepted for publicatio
Combined Relativistic and static analysis for all Delta B=2 operators
We analyse matrix elements of Delta B=2 operators by combining QCD results
with the ones obtained in the static limit of HQET. The matching of all the QCD
operators to HQET is made at NLO order. To do that we have to include the
anomalous dimension matrix up to two loops, both in QCD and HQET, and the one
loop matching for all the Delta B=2 operators. The matrix elements of these
operators are relevant for the prediction of the B-\bar B mixing, B_s meson
width difference and supersymmetric effects in Delta B=2 transitions.Comment: 3 pages, 1 figure. Lattice2001(heavyquark
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