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 $\mathbb{Z}_2$ 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 $t\to {\rm h} c,{\rm h} u$, as well as ${\rm h}\to bs, bd$, 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 $t\to hu,hc$, $h\to \tau e,\tau\mu$ as well as hadronic decays $h\to bs,bd$, 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 $\tan\beta$. 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 $\mu\to e\gamma$.Comment: 33 pages, 8 figures; matches version accepted for publicatio

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 $Q = - 1/3$ quarks, three $Q = 2/3$ 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

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

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 $B^0_s$--$\bar B^0_s$, mixing in the framework of a model with violation of $3\times 3$ unitarity. This violation is associated to the presence of a new $Q=2/3$ isosinglet quark $T$, which mixes both with $t$ and $c$ and has a mass not exceeding 500 GeV. The crucial point is the fact that this framework allows for $\chi\equiv\arg(-V_{ts}V_{cb}V_{tb}^*V_{cs}^*)$ of order $\lambda$, to be contrasted with the situation in the Standard Model, where $\chi$ is constrained to be of order $\lambda^2$. We point out that this scenario implies rare top decays $t\to cZ$ at a rate observable at the LHC and $|V_{tb}|$ significantly different from unity. In this framework, one may also account for the observed size of $D^0$--$\bar D^0$ mixing without having to invoke long distance contributions. It is also shown that in the present scenario, the observed size of $D^0$--$\bar D^0$ mixing constrains $\chi^\prime\equiv\arg(-V_{cd}V_{us}V_{cs}^*V_{ud}^*)$ to be of order $\lambda^4$, which is significantly smaller than what is allowed in generic models with violations of $3\times 3$ unitarity.Comment: 20 pages. References added. Additional observables considered, updated numerical examples, conclusions unchange

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

Pulsating B and Be stars in the Small Magellanic Cloud

Context. Stellar pulsations in main-sequence B-type stars are driven by the κ-mechanism due to the Fe-group opacity bump. The current models do not predict the presence of instability strips in the B spectral domain at very low metallicities. As the metallicity of the SMC is lower than Z = 0.005, it constitutes a very suitable object to test these predictions. Aims. The main objective is to investigate the existence of B-type pulsators at low metallicities, searching for short-term periodic variability in absorption-line B and Be stars in the SMC. The analysis has been performed in a sample of 313 B and Be stars with fundamental astrophysical parameters accurately determined from high-resolution spectroscopy. Methods. Photometric light curves of the MACHO project have been analyzed using standard Fourier techniques and linear and non- linear least squares fitting methods. The position of the pulsating stars in the HR diagram has been used to ascertain their nature and to map the instability regions in the SMC. Results. We have detected 9 absorption-line B stars showing short-period variability, two among them being multiperiodic. One star is most likely a β Cephei variable and the remaining 8 are SPB stars. The SPB instability strip in the SMC is shifted towards higher temperatures than the Galaxy. In the Be star sample, 32 stars are short-period variables, 20 among them multiperiodic. 4.9% of B stars and 25.3% of Be stars are pulsating stars. Conclusions. β Cephei and SPB stars do exist at the SMC metallicity. The fractions of SPB stars and pulsating Be stars in the SMC are lower than in the Galaxy. The fraction of pulsating Be stars in the SMC is much higher than the fraction of pulsating absorption-line B stars, as in the [email protected]; [email protected]; [email protected]