1,082 research outputs found
Vacuum Induced CP Violation Generating a Complex CKM Matrix with Controlled Scalar FCNC
We propose a viable minimal model with spontaneous CP violation in the
framework of a Two Higgs Doublet Model. The model is based on a generalised
Branco-Grimus-Lavoura model with a flavoured symmetry, under
which two of the quark families are even and the third one is odd. The
lagrangian respects CP invariance, but the vacuum has a CP violating phase,
which is able to generate a complex CKM matrix, with the rephasing invariant
strength of CP violation compatible with experiment. The question of scalar
mediated flavour changing neutral couplings is carefully studied. In particular
we point out a deep connection between the generation of a complex CKM matrix
from a vacuum phase and the appearance of scalar FCNC. The scalar sector is
presented in detail, showing that the new scalars are necessarily lighter than
1 TeV. A complete analysis of the model including the most relevant constraints
is performed, showing that it is viable and that it has definite implications
for the observation of New Physics signals in, for example, flavour changing
Higgs decays or the discovery of the new scalars at the LHC. We give special
emphasis to processes like , as well as , which are relevant for the LHC and the ILC.Comment: 36 pages, 11 figure
Flavour Changing Higgs Couplings in a Class of Two Higgs Doublet Models
We analyse various flavour changing processes like , as well as hadronic decays , in the framework of a class
of two Higgs doublet models where there are flavour changing neutral scalar
currents at tree level. These models have the remarkable feature of having
these flavour-violating couplings entirely determined by the CKM and PMNS
matrices as well as . The flavour structure of these scalar currents
results from a symmetry of the Lagrangian and therefore it is natural and
stable under the renormalization group. We show that in some of the models the
rates of the above flavour changing processes can reach the discovery level at
the LHC at 13 TeV even taking into account the stringent bounds on low energy
processes, in particular .Comment: 33 pages, 8 figures; matches version accepted for publicatio
Osteosarcoma extraesquelético. Caso clínico.
El osteosarcoma extraesquelético es un tumor maligno de partes blandas poco frecuente. Es una causa rara de osificación en partes blandas que se distingue de otras entidades por las características clínicas, los estudios de imagen y los exámenes anatomopatológicos. Presentamos un caso clínico en un varón de 64 años, a nivel de muslo. Se realiza una revisión de la bibliografía, señalando las principales características de esta entidad.Extraskeletal osteosarcoma is a rare malignant
soft-tissue neoplasm. The clinical feature, imaging studies
findings and histologic patterns allow the diferential diagno-
sis with other entities. We report a case of a 64 years old man
who had this tumour in his thigh. We make a review of litera-
ture
Controlled Flavour Changing Neutral Couplings in Two Higgs Doublet Models
We propose a class of Two Higgs Doublet Models where there are Flavour
Changing Neutral Currents (FCNC) at tree level, but under control due to the
introduction of a discrete symmetry in the full Lagrangian. It is shown that in
this class of models, one can have simultaneously FCNC in the up and down
sectors, in contrast to the situation encountered in BGL models. The intensity
of FCNC is analysed and it is shown that in this class of models one can
respect all the strong constraints from experiment without unnatural
fine-tuning. It is pointed out that the additional sources of flavour and CP
violation are such that they can enhance significantly the generation of the
Baryon Asymmetry of the Universe, with respect to the Standard Model.Comment: 29 pages, 3 figure
Vector-like Quarks at the Origin of Light Quark Masses and Mixing
We show how a novel fine-tuning problem present in the Standard Model can be
solved through the introduction of a single flavour symmetry G, together with
three quarks, three quarks, as well as a complex singlet
scalar. The symmetry G is extended to the additional fields and it is an exact
symmetry of the Lagrangian, only spontaneously broken by the vacuum. Specific
examples are given and a phenomenological analysis of the main features of the
model is presented. It is shown that even for vector-like quarks with masses
accessible at the LHC, one can have realistic quark masses and mixing, while
respecting the strict constraints on process arising from flavour changing
neutral currents (FCNC). The vector-like quark decay channels are also
described.Comment: 25 pages, no figure
Symmetry Constrained Two Higgs Doublet Models
We study Two-Higgs-Doublet Models (2HDM) where Abelian symmetries have been
introduced, leading to a drastic reduction in the number of free parameters in
the 2HDM. Our analysis is inspired in BGL models, where, as the result of a
symmetry of the Lagrangian, there are tree-level scalar mediated
Flavour-Changing-Neutral-Currents, with the flavour structure depending only on
the CKM matrix. A systematic analysis is done on the various possible schemes,
which are classified in different classes, depending on the way the extra
symmetries constrain the matrices of couplings defining the flavour structure
of the scalar mediated neutral currents. All the resulting flavour textures of
the Yukawa couplings are stable under renormalisation since they result from
symmetries imposed at the Lagrangian level. We also present a brief
phenomenological analysis of the most salient features of each class of
symmetry constrained 2HDM.Comment: 30 pages, 5 Table
Small violations of unitarity, the phase in Bs mixing and visible t->cZ decays at the LHC
We show that it is possible to accommodate the observed size of the phase in
--, mixing in the framework of a model with violation of
unitarity. This violation is associated to the presence of a new
isosinglet quark , which mixes both with and and has a mass
not exceeding 500 GeV. The crucial point is the fact that this framework allows
for of order , to be
contrasted with the situation in the Standard Model, where is
constrained to be of order . We point out that this scenario implies
rare top decays at a rate observable at the LHC and
significantly different from unity. In this framework, one may also account for
the observed size of -- mixing without having to invoke long
distance contributions. It is also shown that in the present scenario, the
observed size of -- mixing constrains
to be of order
, which is significantly smaller than what is allowed in generic
models with violations of unitarity.Comment: 20 pages. References added. Additional observables considered,
updated numerical examples, conclusions unchange
An experimental study of process variables in turning operations of Ti 6Al 4V and Cr Co spherical prostheses
[EN] Ti 6Al 4V and Cr Co alloys are extensively used in manufacturing prostheses due to their biocompatibility, high strength-to-weight ratio and high resistance to corrosion and wear. However, machining operations involving Ti 6Al 4V and Cr Co alloys face a series of difficulties related to their low machinability which complicate the process of controlling the quality levels required in these parts. The main objective of this paper is to study the influence of cutting parameters, machine tool control accuracy and metrology procedures on surface roughness parameters and form errors in contouring operations of Ti 6Al 4V and Cr Co workpieces.
The machining performance of the two biocompatible materials is compared, focusing the study on part quality at low feed per revolution and the stochastic nature of plastic deformations at this regime. The results showed a better surface roughness control for Ti 6Al 4V, whereas for Cr Co alloys, the performance presents high variability.
In the case of form errors (sphericity), contouring errors and metrology procedures are important factors to be considered for quality assurance. In addition, the study analyses the correlation of the machining performance with different sensor signals acquired from a low cost non-intrusive multi-sensor, showing a high correlation of signals from acoustic emission sensors and accelerometers in the machining of spherical features on Ti 6Al 4V parts. The findings of this research work can be taken into account when designing prostheses components and planning their manufacturing processes.This work was partially supported by Fundacio Caixa-Castello Bancaixa under the research project INV-2009-39. The authors are grateful to Miguel Angel Aymerich and Arcadi Sanz, who assisted in the experimental part. The authors would also like to extend their acknowledgments to Lafitt Company for its collaboration. 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