461 research outputs found
Rare top decay and CP violation in THDM
We discuss the formalism of two Higgs doublet model type III with CP
violation from CP-even CP-odd mixing in the neutral Higgs bosons. The flavor
changing interactions among neutral Higgs bosons and fermions are presented at
tree level in this type of model. These assumptions allow the study rare top
decays mediated by neutral Higgs bosons, particularly we are interested in
. For this process we estimated upper bounds of the
branching ratios of the order of
for a neutral Higgs boson mass of 125 GeV and
, 1.5, 2, 2.5. For the case of the
number of possible events is estimated from 1 to 10 events which could be
observed in future experiments at LHC with a luminosity of 300
and 14 GeV for the energy of the center of mass. Also we
estimate that the number of events for the process in
different scenarios is of order of .Comment: 8 pages, 5 figure
A Geometric Representation for the Proca Model
The Proca model is quantized in an open-path dependent representation that
generalizes the Loop Representation of gauge theories. The starting point is a
gauge invariant Lagrangian that reduces to the Proca Lagrangian when certain
gauge is selected.Comment: 10 pages, Late
Neutrino masses and mixing parameters in a left-right model with mirror fermions
In this work we consider a left-right model containing mirror fermions with
gauge group SU(3). The model has several free parameters which here we have
calculated by using the recent values for the squared-neutrino mass
differences. Lower bound for the mirror vacuum expectation value helped us to
obtain crude estimations for some of these parameters. Also we estimate the
order of magnitude of the masses of the standard and mirror neutrinos.Comment: 13 pages, version submitted to European Physical Journal
Serendipitous discovery of RR Lyrae stars in the Leo V ultra-faint galaxy
During the analysis of RR Lyrae stars discovered in the High cadence
Transient Survey (HiTS) taken with the Dark Energy Camera at the 4-m telescope
at Cerro Tololo Inter-American Observatory, we found a group of three very
distant, fundamental mode pulsator RR Lyrae (type ab). The location of these
stars agrees with them belonging to the Leo V ultra-faint satellite galaxy, for
which no variable stars have been reported to date. The heliocentric distance
derived for Leo V based on these stars is 173 +/- 5 kpc. The pulsational
properties (amplitudes and periods) of these stars locate them within the locus
of the Oosterhoff II group, similar to most other ultra-faint galaxies with
known RR Lyrae stars. This serendipitous discovery shows that distant RR Lyrae
stars may be used to search for unknown faint stellar systems in the outskirts
of the Milky Way.Comment: Accepted in ApJ Letter
Caracterización de prácticas de enseñanza universitaria
La investigación trató sobre la pregunta seleccionada y referida a la forma como podía describir y caracterizarse las construcciones metodológicas en las prácticas de enseñanza del área de la educación seleccionada en el estudio. Se acudió a la investigación acción en colaboración, como modalidad desde la cual, el profesor explora las prácticas educativas de las cuales es responsable, reflexiona sobre ellas, identifica problemas y establece políticas de acción. Para el estudio, se contó con la participación de cuatro docentes de la carrera de Pedagogía Infantil. Desde los resultados, se pudo evidenciar que las construcciones metodológicas de los docentes son acciones singulares, creativas y contextuales en las cuales, se renuncia a homogenizar, idealizar o estandarizar las acciones metódicas en el aula. Existe una categoría que se hace visible en los diferentes momentos de la construcción metodológica: el Estudiante Universitario como sujeto del aprendizaje. La principal conclusión se ubica en la importancia y necesidad de generar estos procesos reflexivos en el escenario de la educación superior, en donde existen mayores vacíos conceptuales e investigativos en cuanto a la caracterización de las prácticas de enseñanza universitarias
The Type IIn Supernova SN 2010bt: The Explosion of a Star in Outburst
Indexación: Scopus.It is well known that massive stars (M > 8 M ) evolve up to the collapse of the stellar core, resulting in most cases in a supernova (SN) explosion. Their heterogeneity is related mainly to different configurations of the progenitor star at the moment of the explosion and to their immediate environments. We present photometry and spectroscopy of SN 2010bt, which was classified as a Type IIn SN from a spectrum obtained soon after discovery and was observed extensively for about 2 months. After the seasonal interruption owing to its proximity to the Sun, the SN was below the detection threshold, indicative of a rapid luminosity decline. We can identify the likely progenitor with a very luminous star (log L/L ≈ 7) through comparison of Hubble Space Telescope images of the host galaxy prior to explosion with those of the SN obtained after maximum light. Such a luminosity is not expected for a quiescent star, but rather for a massive star in an active phase. This progenitor candidate was later confirmed via images taken in 2015 (∼5 yr post-discovery), in which no bright point source was detected at the SN position. Given these results and the SN behavior, we conclude that SN 2010bt was likely a Type IIn SN and that its progenitor was a massive star that experienced an outburst shortly before the final explosion, leading to a dense H-rich circumstellar environment around the SN progenitor. © 2018. The American Astronomical Society. All rights reserved.https://iopscience.iop.org/article/10.3847/1538-4357/aac51
Molecular gas at supernova local environments unveiled by EDGE
CO observations allow estimations of the gas content of molecular clouds,
which trace the reservoir of cold gas fuelling star formation, as well as to
determine extinction via H column density, N(H). Here, we studied
millimetric and optical properties at 26 supernovae (SNe) locations of
different types in a sample of 23 nearby galaxies by combining molecular
CO (J = 1 0) resolved maps from the EDGE survey and
optical Integral Field Spectroscopy from the CALIFA survey. We found an even
clearer separation between type II and type Ibc SNe in terms of molecular gas
than what we found in the optical using H emission as a proxy for
current SF rate, which reinforces the fact that SNe Ibc are more associated
with SF-environments. While A at SN locations is similar for SNe II and SNe
Ibc, and higher compared to SNe Ia, N(H) is significantly higher for SNe
Ibc than for SNe II and SNe Ia. When compared to alternative extinction
estimations directly from SN photometry and spectroscopy, we find that our SNe
Ibc have also redder color excess but showed standard Na I D absorption
pseudo-equivalent widths (1 \AA). In some cases we find no extinction
when estimated from the environment, but high amounts of extinction when
measured from SN observations, which suggests that circumstellar material or
dust sublimation may be playing a role. This work serves as a benchmark for
future studies combining last generation millimeter and optical IFS instruments
to reveal the local environmental properties of extragalactic SNe.Comment: MNRAS accepted, 17 pages, 8 Figures, 4 Table
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