6,313 research outputs found
semileptonic form factors with Twisted Mass fermions
We present a lattice QCD determination of the vector and scalar form factors
of the semileptonic decay which are relevant for the
extraction of the CKM matrix element from experimental data. Our
results are based on the gauge configurations produced by the European Twisted
Mass Collaboration with dynamical fermions, which include in the
sea, besides two light mass degenerate quarks, also the strange and the charm
quarks. We use data simulated at three different values of the lattice spacing
and with pion masses as small as MeV. Our final result for the vector
form factor at zero momentum transfer is , where the
uncertainty is both statistical and systematic combined in quadrature. Using
the latest experimental value of from decays, we
obtain , which allows to test the unitarity constraint
of the Standard Model below the permille level once the determination of
from superallowed nuclear decays is adopted. A slight
tension with unitarity at the level of standard deviations is
observed. Moreover we present our results for the semileptonic scalar
and vector form factors in the whole range of values of
the squared four-momentum transfer measured in decays,
obtaining a very good agreement with the momentum dependence of the
experimental data. We provide a set of synthetic data points representing our
results for the vector and scalar form factors at the physical point for
several selected values of .Comment: 37 pages, 5 tables, 9 figures; version to appear in PR
\Delta S=2 and \Delta C=2 bag parameters in the SM and beyond from Nf=2+1+1 twisted-mass LQCD
We present unquenched lattice QCD results for the matrix elements of
four-fermion operators relevant to the description of the neutral K and D
mixing in the Standard Model and its extensions. We have employed simulations
with Nf = 2 + 1 + 1 dynamical sea quarks at three values of the lattice
spacings in the interval 0.06 - 0.09 fm and pseudoscalar meson masses in the
range 210 - 450 MeV. Our results are extrapolated to the continuum limit and to
the physical pion mass. Renormalization constants have been determined
non-perturbatively in the RI-MOM scheme. In particular, for the Kaon
bag-parameter, which is relevant for the \overline{K}^0-K^0 mixing in the
Standard Model, we obtain B_K^{RGI} = 0.717(24).Comment: Added comments to error budget discussion; fig.19 corrected. Version
to appear in PR
Mixed-mode impedance and reflection coefficient of two-port devices
From the point of view of mixed-mode scattering parameters, Smm, a two-port device can be excited using different driving conditions. Each condition leads to a particular set of input reflection and input impedance coefficient definitions that should be carefully applied depending on the type of excitation and symmetry of the two-port device. Therefore, the aim of this paper is to explain the general analytic procedure for the evaluation of such reflection and impedance coefficients in terms of mixed-mode scattering parameters. Moreover, the driving of a two-port device as a one-port device is explained as a particular case of a two-port mixed-mode excitation using a given set of mixed-mode loads. The theory is applied to the evaluation of the quality factor, Q, of symmetrical and non- symmetrical inductors.Ministerio de Innovación y Ciencia TEC2010-14825/MIC, TEC2010-21484Junta de AndalucÃa TIC-253
Monoartritis gotosa de muñeca asociada a necrosis del semilunar: a propósito de un caso clÃnico
Se presenta un caso de monoartritis de muñeca asociada a imágenes radiológicas
de necrosis avascular del semilunar que, tras biopsia de la sinovial, se diagnostica de artritis gotosa.
Esta asociación es rara. La alteración metabólica que se produce en la gota da lugar a una sinovitis,
que provoca un aumento de presión intraarticular. Esta hiperpresión en el carpo podrÃa determinar
una necrosis isquémica del semilunar, pero con una evolución diferente a la enfermedad de
Kienböck. Es por ello que una artropatÃa metabólica, debe considerarse como diagnóstico diferencial
con la enfermedad de Kiemböck cuando se asocian imágenes geódicas en el carpo y radio.We report a case of monoarthritis of the wrist associated with radiological signs
of avascular necrosis of lunate. The synovial biopsy confirmed the diagnosis of gout. This is a
very rare association. Differential diagnosis should be make with a metabolic arthritis when bone
necrosis is associated with osseous lesions in carpal bones and radius
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