Anomaly-free U(1) gauge symmetries in neutrino seesaw flavor models

Adding right-handed neutrino singlets and/or fermion triplets to the particle content of the Standard Model allows for the implementation of the seesaw mechanism to give mass to neutrinos and, simultaneously, for the construction of anomaly-free gauge group extensions of the theory. We consider Abelian extensions based on an extra U(1)_X gauge symmetry, where X is an arbitrary linear combination of the baryon number B and the individual lepton numbers L_{e,mu,tau}. By requiring cancellation of gauge anomalies, we perform a detailed analysis in order to identify the charge assignments under the new gauge symmetry that lead to neutrino phenomenology compatible with current experiments. In particular, we study how the new symmetry can constrain the flavor structure of the Majorana neutrino mass matrix, leading to two-zero textures with a minimal extra fermion and scalar content. The possibility of distinguishing different gauge symmetries and seesaw realizations at colliders is also briefly discussed.Comment: 12 pages, 2 figures, 7 tables; comments and references added, a new subsection with nonstandard interactions of neutrinos included; final version to appear in Phys. Rev.

Minimal anomaly-free chiral fermion sets and gauge coupling unification

We look for minimal chiral sets of fermions beyond the standard model that are anomaly free and, simultaneously, vectorlike particles with respect to colour SU(3) and electromagnetic U(1). We then study whether the addition of such particles to the standard model particle content allows for the unification of gauge couplings at a high energy scale, above $5.0 \times 10^{15}$ GeV so as to be safely consistent with proton decay bounds. The possibility to have unification at the string scale is also considered. Inspired in grand unified theories, we also search for minimal chiral fermion sets that belong to SU(5) multiplets. Restricting to representations up to dimension 50, we show that some of these sets can lead to gauge unification at the GUT and/or string scales.Comment: 13 pages, 5 figures, 8 tables; Comments and references added, final version to appear in Phys. Rev.

Fixing the U-band photometry of Type Ia supernovae

We present previously unpublished photometry of supernovae 2003gs and 2003hv. Using spectroscopically-derived corrections to the U-band photometry, we reconcile U-band light curves made from imagery with the Cerro Tololo 0.9-m, 1.3-m and Las Campanas 1-m telescopes. Previously, such light curves showed a 0.4 mag spread at one month after maximum light. This gives us hope that a set of corrected ultraviolet light curves of nearby objects can contribute to the full utilization of rest frame U-band data of supernovae at redshift ~0.3 to 0.8. As pointed out recently by Kessler et al. in the context of the Sloan Digital Sky Survey supernova search, if we take the published U-band photometry of nearby Type Ia supernovae at face value, there is a 0.12 mag U-band anomaly in the distance moduli of higher redshift objects. This anomaly led the Sloan survey to eliminate from their analyses all photometry obtained in the rest frame U-band. The Supernova Legacy Survey eliminated observer frame U-band photometry, which is to say nearby objects observed in the U-band, but they used photometry of high redshift objects no matter in which band the photons were emitted.Comment: 25 pages, 9 figures, accepted for publication in the Astronomical Journa

Compositional uniformity, domain patterning and the mechanism underlying nano-chessboard arrays

We propose that systems exhibiting compositional patterning at the nanoscale, so far assumed to be due to some kind of ordered phase segregation, can be understood instead in terms of coherent, single phase ordering of minority motifs, caused by some constrained drive for uniformity. The essential features of this type of arrangements can be reproduced using a superspace construction typical of uniformity-driven orderings, which only requires the knowledge of the modulation vectors observed in the diffraction patterns. The idea is discussed in terms of a simple two dimensional lattice-gas model that simulates a binary system in which the dilution of the minority component is favored. This simple model already exhibits a hierarchy of arrangements similar to the experimentally observed nano-chessboard and nano-diamond patterns, which are described as occupational modulated structures with two independent modulation wave vectors and simple step-like occupation modulation functions.Comment: Preprint. 11 pages, 11 figure

Manteniendo lazos vía Web: El Caso de las Comunidades Mexicanas de Emigrantes en los EUA

Migration has gained considerable attention in the past few years all over the world. The migratory phenomenon has already affected many countries and is likely to deeply reshape forever their societies and regulations. Of particular interest is the migratory flow from Mexico to the USA, which is identified as one of the most important labor related worldwide. It has been found that migration can potentially have a major impact on individuals leaving home as they can experience nostalgic feelings. As a result of physical distance, family members look for closeness to prevail by maintaining in permanent communication. This paper offers an analysis of web sites from Mexican diasporic communities living in the US, aiming to reveal the level of presence of those communities on the Internet as well as to characterize the support they provide for living-away members of the communities

Estudio comparativo de equipos fijos de pedestal y su aplicación en la detección del tráfico incontrolado de material radiactivo en aeropuertos

En este trabajo se analiza la respuesta de tres equipos comerciales, diseñados para detectar el tráfico ilícito o el desplazamiento involuntario de material radiactivo en aeropuertos cuando es transportado por los pasajeros. Se han comparado tres instrumentos fijos de pedestal: el equipo APM de Bicron, el equipo GR-606 de Exploranium y el equipo FHT-1372 de Thermo Eberline. En esta evaluación inicial, realizada en el Laboratorio de Ingeniería Nuclear de la Escuela de Caminos, Canales y Puertos, se observó que el equipo FHT-1372 presentó una respuesta de detección más rápida, sensible y permitió la medida de tasa de dosis total y tasa de dosis artificial. Este equipo fue instalado en la salida de la aduana de pasajeros del aeropuerto internacional de Barajas durante un periodo operativo de 108 días en el año 2002 y pasaron un total de 1.339.931 personas. Este periodo se dividió en 5 sesiones para poder establecer los niveles de investigación adecuados para detectar una posible incidencia de material radiactivo, que finalmente se fijaron en 110 nSv/h para la tasa de dosis total y 25 nSv/h para la tasa de dosis artificial. Durante dicho periodo se detectaron 39 posibles incidencias por encima del límite de investigación establecido para las diferentes sesiones, 5 de ellas con un valor 10 veces superior al fondo ambiental de la sala donde se instaló el equipo (alrededor de 90 nSv/h) y ninguna superó el nivel de 100 μSv/h a 1 m de distancia que la Organización Internacional de la Energía Atómica (OIEA) establece como límite para el transporte lícito de material radiactivo

New Gogny interaction suitable for astrophysical applications

The D1 family of parametrizations of the Gogny interaction commonly suffers from a rather soft neutron matter equation of state that leads to maximal masses of neutron stars well below the observational value of two solar masses. We propose a reparametrization scheme that preserves the good properties of the Gogny force but allows one to tune the density dependence of the symmetry energy, which, in turn, modifies the predictions for the maximum stellar mass. The scheme works well for D1M, and leads to a new parameter set, dubbed D1M⁎. In the neutron-star domain, D1M⁎predicts a maximal mass of two solar masses and global properties of the star in harmony with those obtained with the SLy4 Skyrme interaction. By means of a set of selected calculations in finite nuclei, we check that D1M⁎performs comparably well to D1M in several aspects of nuclear structure in nucleiThe work of LMR was supported by Spanish Ministry of Economy and Competitiveness (MINECO) Grants No.FPA2015-65929-P and FIS2015-63770-P. C.G., M.C., and X.V. were partially sup-ported by Grant FIS2014-54672-P from MINECO and FEDER, Grant 2014SGR-401 from Generalitat de Catalunya, and Project MDM-2014-0369 of ICCUB (Unidad de Excelencia María de Maeztu) from MINECO. C.G. also acknowledges Grant BES-2015-074210 from MINEC

VLBA determination of the distance to nearby star-forming regions I. The distance to T Tauri with 0.4% accuracy

In this article, we present the results of a series of twelve 3.6-cm radio continuum observations of T Tau Sb, one of the companions of the famous young stellar object T Tauri. The data were collected roughly every two months between September 2003 and July 2005 with the Very Long Baseline Array (VLBA). Thanks to the remarkably accurate astrometry delivered by the VLBA, the absolute position of T Tau Sb could be measured with a precision typically better than about 100 micro-arcseconds at each of the twelve observed epochs. The trajectory of T Tau Sb on the plane of the sky could, therefore, be traced very precisely, and modeled as the superposition of the trigonometric parallax of the source and an accelerated proper motion. The best fit yields a distance to T Tau Sb of 147.6 +/- 0.6 pc. The observed positions of T Tau Sb are in good agreement with recent infrared measurements, but seem to favor a somewhat longer orbital period than that recently reported by Duchene et al. (2006) for the T Tau Sa/T Tau Sb system.Comment: 24 pages, 3 pages, AASTEX format, accepted for publication in Ap