277 research outputs found
Static quarks with improved statistical precision
We present a numerical study for different discretisations of the static
action, concerning cut-off effects and the growth of statistical errors with
Euclidean time. An error reduction by an order of magnitude can be obtained
with respect to the Eichten-Hill action, for time separations beyond 1.3 fm,
keeping discretization errors small. The best actions lead to a big improvement
on the precision of the quark mass Mb and F_Bs in the static approximation.Comment: 3 pages, 4 figures, Lattice2003(heavy
Non-perturbative scaling tests of twisted mass QCD
We present a scaling study of lattice QCD with O(a) improved Wilson fermions
and a chirally twisted mass term. In order to get precise results with a
moderate computational effort, we have considered a system of physical size of
0.75^3 * 1.5 fm^4 with Schroedinger functional boundary conditions in the
quenched approximation. Looking at meson observables in the pseudoscalar and
vector channels, we find that O(a) improvement is effective and residual cutoff
effects are fairly small.Comment: 5 pages, 4 figures, Lattice 2000 (Improvement and Renormalization),
two misprints correcte
Cutoff effects in twisted mass lattice QCD
We present a first numerical study of lattice QCD with O(a) improved Wilson
quarks and a chirally twisted mass term. Renormalized correlation functions are
derived from the Schroedinger functional and evaluated in an intermediate
space-time volume of size 0.75^3 x 1.5 fm^4. In the quenched approximation
precise results are then obtained with a moderate computational effort,
allowing for a detailed study of the continuum approach. The latter is
discussed in terms of observables which converge to meson masses and decay
constants in the limit of large space-time volume. In the O(a) improved theory
we find residual cutoff effects to be at the level of a few percent for lattice
spacings of about 0.1 fm.Comment: 20 pages, 5 figures. Comments about the uncertainties on improvement
coefficients adde
Quenched twisted mass QCD at small quark masses and in large volume
As a test of quenched lattice twisted mass QCD, we compute the
non-perturbatively O() improved pseudoscalar and vector meson masses and the
pseudoscalar decay constant down to at
in large volume. We check the absence of exceptional configurations
and -- by further data at -- the size of scaling violations. The
CPU time cost for reaching a given accuracy is close to that with ordinary
Wilson quarks at and grows smoothly as
decreases.Comment: 4 pages, 3 figures, to appear in Nucl. Phys. B (Proc. Suppl.
Heavy pseudoscalar-meson decay constants with strangeness from the extended nonlocal chiral-quark model
We study the weak-decay constants for the heavy pseudoscalar mesons, D, Ds,
B, and Bs. For this purpose, we employ the extended nonlocal chiral-quark model
(ExNLChQM), motivated by the heavy-quark effective field theory as well as the
instanton-vacuum configuration. In addition to the heavy-quark symmetry and the
nonlocal interactions between quarks and pseudoscalar mesons in ExNLChQM, a
correction for the strange-quark content inside Ds and Bs is also taken into
account and found to be crucial to reproduce the empirical values. From those
numerical results, we obtain f_{D,Ds,B,Bs}=(207.53, 262.56, 208.13, 262.39)
MeV, which are in good agreement with experimental data and other theoretical
estimations. Using those numerical results, we compute the CKM matrix elements
and the Cabibbo angle, using various mesonic and leptonic heavy-meson decay
channels, resulting in
(|V_{cd}|,|V_{cs}|,|V_{ub}|,|V_{td}|/|V_{ts}|)=(0.224,0.968,<5.395*10^{-3},0.215)
and theta_C=12.36^o which are well compatible with available data.Comment: 12 pages, 7 figures, accepted for publication in Mod. Phys. Lett.
Towards a precision computation of f_Bs in quenched QCD
We present a computation of the decay constant f_Bs in quenched QCD. Our
strategy is to combine new precise data from the static approximation with an
interpolation of the decay constant around the charm quark mass region. This
computation is the first step in demonstrating the feasability of a strategy
for f_B in full QCD. The continuum limits in the static theory and at finite
mass are taken separately and will be further improved.Comment: Lattice2003(heavy), 3 pages, 2 figure
Categories of Product Innovations. A Prospective Categorization Framework for Innovation Projects in Early Development Phases Based on Empirical Data
AbstractMost of the categorization frameworks for innovation projects in early development phases are not designed for supporting the product engineer in decision making and leave space for further improvement. Based on empirical data from 13 innovation projects, the authors introduce a novel categorization framework for innovation projects and discuss the relevance of identified key criteria. The focus is to provide a fundamental understanding of the varieties of product innovation projects and establish a basis for decision support frameworks regarding the adoption of tools and methods
Non-perturbative Heavy Quark Effective Theory
We explain how to perform non-perturbative computations in HQET on the
lattice. In particular the problem of the subtraction of power-law divergences
is solved by a non-perturbative matching of HQET and QCD. As examples, we
present a full calculation of the mass of the b-quark in the combined static
and quenched approximation and outline an alternative way to obtain the B-meson
decay constant at lowest order. Since no excessively large lattices are
required, our strategy can also be applied including dynamical fermions.Comment: 27 pages including figures and tables, latex2e; version published in
JHEP, typos corrected and 1 reference adde
Quark bilinear step scaling functions and their continuum limit extrapolation
Some new results on nonperturbative renormalisation of quark bilinears in
quenched QCD with Schroedinger Functional techniques are presented. Special
emphasis is put on a study of the universality of the continuum limit for step
scaling functions computed with different levels of O(a) improvement.Comment: Lattice2003(improve), 3 pages, 3 figure
- …