1,547 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
Phenomenological Implications of Supersymmetric Family Non-universal U(1)-prime Models
We construct a class of anomaly-free supersymmetric U(1)' models that are
characterized by family non-universal U(1)' charges motivated from E_6
embeddings. The family non-universality arises from an interchange of the
standard roles of the two SU(5) 5* representations within the 27 of E_6 for the
third generation. We analyze U(1)' and electroweak symmetry breaking and
present the particle mass spectrum. The models, which include additional Higgs
multiplets and exotic quarks at the TeV scale, result in specific patterns of
flavor-changing neutral currents in the b to s transitions that can accommodate
the presently observed deviations inthis sector from the SM predictions.Comment: 25 pages, 3 figure
Experimental investigation and monitoring of a polypropylene-based fiber reinforced concrete road pavement
Abstract In this work, basic guidelines are provided for the design of a polypropylene-based fiber reinforced concrete (PFRC) road pavement, as applied in an actual testing section resting inside a tunnel of the "Quadrilatero Marche-Umbria" road empowerment project, Italy. Results of a six-month monitoring carried out on actual traffic loads are also presented, as a feedback to the designing stage. Monitoring encompasses direct measurement of the strain level inside the cast as well as acoustic measurement. It is shown that the fiber reinforced concrete technology provides an efficient, safe as well as cost-effective design solution for roadways, especially inside tunnels
Effective thermal properties of fibre reinforced materials
The thermal behaviour of an elastic matrix reinforced with synthetic micro or macro fibres subjected to a constant heat flow is investigated in the present work. Steady-state condition for the heat flux is considered and isotropic thermal conductivity for both the matrix and fibres is assumed. Owing to the geometry of the system, reference is made to bipolar cylindrical coordinates.
Various boundary conditions can be considered on the contours of the fibres. In particular, for a matrix reinforced with two fibres taken as insulated inclusions, a vanishing heat flow across the contour of the fibres must be imposed.
After the temperature field has benn determined analytically, a homogeneization procedure is performed in order to find the equivalent thermal properties of the fibre reinforced composite material
Composition-induced structural phase transitions in the (Ba1xLax)2In2O5+x (0pxp0.6) system
Composition-induced structural phase changes across the high temperature, fast oxide ion conducting (Ba1xLax)2In2O5+x, 0pxp0.6, system have been carefully analysed using hard mode infrared (IR) powder absorption spectroscopy, X-ray powder diffraction and electron diffraction. An orthorhombic brownmillerite to three-dimensionally disordered cubic perovskite phase transition in this system is signalled by a drastic change in slope of both wavenumber and average line widths of IR spectra as a function of composition. Some evidence is found for the existence of an intermediate tetragonal phase (previously reported to exist from electron diffraction data) around x 0:2: The new spectroscopic data have been used to compare microscopic and macroscopic strain parameters arising from variation in composition. The strain and spectroscopic data are consistent with firstorder character for the tetragonal-orthorhombic transition, while the cubic-tetragonal transition could be continuous. Differences between the variation with composition of spectral parameters and of macroscopic strain parameters are consistent with a substantial order/disorder component for the transitions. There is also evidence for precursor effects within the cubic structure before symmetry is broken
Tensor form factor of and decays with twisted-mass fermions
We present the first lattice Nf=2+1+1 determination of the tensor form factor
corresponding to the semileptonic and rare
decays as a function of the squared 4-momentum transfer . Together with
our recent determination of the vector and scalar form factors we complete the
set of hadronic matrix elements regulating the semileptonic and rare transitions within and beyond the Standard Model, when a non-zero
tensor coupling is possible. Our analysis is based on the gauge configurations
produced by ETMC with Nf=2+1+1 flavors of dynamical quarks, which include in
the sea, besides two light mass-degenerate quarks, also the strange and charm
quarks with masses close to their physical values. We simulated at three
different values of the lattice spacing and with pion masses as small as 220
MeV. The matrix elements of the tensor current are determined for plenty of
kinematical conditions in which parent and child mesons are either moving or at
rest. As in the case of the vector and scalar form factors, Lorentz symmetry
breaking due to hypercubic effects is clearly observed also in the data for the
tensor form factor and included in the decomposition of the current matrix
elements in terms of additional form factors. After the extrapolations to the
physical pion mass and to the continuum and infinite volume limits we determine
the tensor form factor in the whole kinematical region accessible in the
experiments. A set of synthetic data points, representing our results for
for several selected values of , is provided and the
corresponding covariance matrix is also available. At zero four-momentum
transfer we get and ,
which correspond to and .Comment: 22 pages, 7 figures, 10 tables. Conclusions unchanged. Version to
appear in PRD. arXiv admin note: text overlap with arXiv:1710.07121 and
substantial text overlap with arXiv:1706.0301
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