Probing BSM Physics with CP-violation, Neutrinos and White Dwarfs

While the Standard Model remains the best theory to describe elementary particles and their interactions, there are still some unresolved issues that cannot be addressed within its current framework. Right handed neutrinos are introduced to the Standard Model to explain the observed active neutrino masses. If CP is violated during their radiative decays an asymmetry between two circularly–polarised photons can be generated. The CP asymmetry is somehow connected to circular polarisation. Therefore, observations of such polarised signal potentially lead to a measurement of the CP violation in the process. Here, we provide the connection between these two asymmetries for both, Dirac and Majorana neutrinos. We then apply this formalism to a minimal seesaw model and give the CP asymmetry in terms of a series of Jarlskog-like parameter. We also provide the formalism to study the changes in the polarisation of photons at any energy, since the intensity of such circularly polarised signal could change as it propagates through the Universe. Finally, we pay attention to the dark matter paradigm. We discuss the capture of dark matter in compact stellar objects as complementary to direct detection searches. We particularly work with white dwarfs (WD) since due to their abundance and high temperatures they one of the best observed compact objects proposed as cosmic laboratories for studying physical processes happening at very extreme conditions that cannot be achieved at terrestrial laboratories. Using an observed WD from the Messier 4 globular cluster, we set constraints on the DM interactions

Constraining dark matter interactions mediated by a light scalar with white dwarfs

Observations of white dwarfs in dark matter-rich environments can provide strong limits on the strength of dark matter interactions. Here we apply the recently improved formalism of the dark matter capture rate in white dwarfs to a general model in which dark matter interacts with the white dwarf ion components via a light scalar mediator. We compute the dark matter capture rate in the optically thin limit in a cold white dwarf from the globular cluster Messier. We then estimate the threshold cross-section, which significantly varies as a function of the light scalar mediator mass $m_\phi$ in the range of 0.05\, m_\chim_\chi. We also show that the bounds obtained from the dark matter capture in a white dwarf from the globular cluster Messier 4 are complementary to direct detection experiments and particularly strong in the sub-GeV regime.Comment: 6 pages, 2 figure

Exploring the dark sectors via the cooling of white dwarfs

As dense and hot bodies with a well-understood equation of state, white dwarfs offer a unique opportunity to investigate new physics. In this paper, we examine the role of dark sectors, which are extensions of the Standard Model of particle physics that are not directly observable, in the cooling process of white dwarfs. Specifically, we examine the role of a dark photon, within the framework of a three-portal Model, in enhancing the neutrino emission during the cooling process of white dwarfs. We compare this scenario to the energy release predicted by the Standard Model. By analyzing the parameter space of dark sectors, our study aims to identify regions that could lead to significant deviations from the expected energy release of white dwarfs.Comment: 9 pages, 5 figure

CP violation in neutral lepton transition dipole moment

The CP violation in the neutrino transition electromagnetic dipole moment is discussed in the context of the Standard Model with an arbitrary number of right-handed singlet neutrinos. A full one-loop calculation of the neutrino electromagnetic form factors is performed in the Feynman gauge. A non-zero CP asymmetry is generated by a required threshold condition for the neutrino masses along with non-vanishing CP violating phases in the lepton flavour mixing matrix. We follow the paradiagm of CP violation in neutrino oscillations to parametrise the flavour mixing contribution into a series of Jarlskog-like parameters. This formalism is then applied to a minimal seesaw model with two heavy right-handed neutrinos denoted N1 and N2. We observe that the CP asymmetries for decays into light neutrinos N → νγ are extremely suppressed, maximally around 10−17. However the CP asymmetry for N2 → N1γ can reach of order unity. Even if the Dirac CP phase δ is the only source of CP violation, a large CP asymmetry around 10−5–10−3 is comfortably achieved

Líquenes como bioindicadores de contaminación aérea en el corredor metropolitano de la ciudad de Guatemala.

El incremento en las sustancias tóxicas a la atmósfera en la ciudad de Guatemala ha generado un empeoramiento paulatino de la calidad del aire. Por lo tanto, es necesaria la incorporación de un sistema de monitoreo que sea económico y que permita determinar las áreas de la ciudad con altos índices de contaminación aérea, para posteriormente tomar medidas adecuadas para su mitigación. En este sentido, el presente estudio categorizó los niveles de contaminación aérea por medio del Índice de Pureza Atmosférica (IPA), complementado con coberturas de cada especie, el Factor de Clasificación Ambiental (ECF) y el cambio en la diversidad de líquenes en árboles de jacaranda en 32 puntos del corredor metropolitano en la ciudad de Guatemala. Los resultados reportan 16 familias, 23 géneros y 65 especies de líquenes, de las cuales 26 son nuevos registros para el país y 5 para la ciudad. Los valores de IPA variaron de 4.5 a 25.5 indicando homogeneidad en los índices de contaminación aérea a lo largo del corredor metropolitano. En los puntos P5 Instituto Normal para Señoritas Centro América (INCA) y P13 (Parroquia Santa Marta) se obtuvieron los menores valores de IPA por lo que son los puntos con mayor grado de contaminación aérea; y los puntos P28 (Universidad Francisco Marroquín) y P21 (Avenida las Américas 1) obtuvieron los mayores siendo las áreas menos contaminadas. La incorporación del valor de cobertura al IPA, permite categorizar las áreas a una escala más fina, dándole mayor peso a especies toxitolerantes y toxisensibles. Estos resultados evidencian que los líquenes pueden complementar mediciones físico- químicas de contaminación aérea, especialmente en puntos en donde no se cuenta con equipo para ello y pueden indicar lugares con problemas ambientales que necesiten investigación instrumental, como los puntos P5 y P13. Así mismo, se proponen 10 especies foliosas de líquenes para ser utilizadas como indicadoras de contaminación aérea en futuras investigaciones

Vortex Creep Heating vs. Dark Matter Heating in Neutron Stars

Dark matter particles captured in neutron stars deposit their energy as heat. This DM heating effect can be observed only if it dominates over other internal heating effects in NSs. In this work, as an example of such an internal heating source, we consider the frictional heating caused by the creep motion of neutron superfluid vortex lines in the NS crust. The luminosity of this heating effect is controlled by the strength of the interaction between the vortex lines and nuclei in the crust, which can be estimated from the many-body calculation of a high-density nuclear system as well as through the temperature observation of old NSs. We show that both the temperature observation and theoretical calculation suggest that the vortex creep heating dominates over the DM heating. The vortex-nuclei interaction must be smaller than the estimated values by several orders of magnitude to overturn this.Comment: 8 pages, 2 figure

Thermal Leptogenesis in the Minimal Gauged U(1)Lμ−LτU(1)_{L_\mu-L_\tau} Model

We discuss the thermal leptogenesis mechanism within the minimal gauged U(1)$_{L_\mu-L_\tau}$ model to explain the observed baryon asymmetry of the Universe (BAU). In such framework, the phases of the Pontecorvo-Maki-Nakagawa-Sakata neutrino mixing matrix and the sum of the Standard Model neutrino masses are predictable because of a restricted neutrino mass matrix structure. Additionally, in the context of thermal leptogenesis, the BAU can be computed in terms of the three remaining free variables that parameterise the right-handed neutrino masses and their Yukawa couplings to the Higgs and lepton doublets. We identify the ranges of such parameters for which the correct BAU can be reproduced. We adopt the formalism of the density matrix equations to fully account for flavour effects and consider the decays of all the three right-handed neutrinos. Our analysis reveals that thermal leptogenesis is feasible within a wide parameter space, specifically for Yukawa couplings ranging from approximate unity to $\mathcal{O}(0.03-0.05)$ and mass of the lightest right-handed neutrino $M_1\gtrsim 10^{11-12}\,\text{GeV}$, setting a leptogenesis scale in the considered model which is higher than that of the non-thermal scenario.Comment: 22 pages, 4 figure

Contribución al conocimiento de los encinos (Quercus: Fagaceae) en los departamentos de Alta Verapaz, Baja Verapaz y Petén, Guatemala

Las especies del género Quercus son de importancia ecológica y económica dentro de los bosques donde se desarrollan. Pueden encontrarse desde zonas cálidas y secas hasta selvas lluviosas. Estos bosques, también son reconocidos por presentar alto grado de endemismo y gran número de interacciones ecológicas. Sin embargo, en Guatemala las especies de encino han sido poco estudiadas y están fuertemente amenazadas; a pesar de poseer un alto potencial para aprovechamiento, manejo y uso en la restauración de ecosistemas. Este estudio se orientó hacia la actualización de la riqueza y distribución geográfica de las especies de encino para Alta Verapaz, Baja Verapaz y Petén, a partir de la revisión de registros en herbarios nacionales, bases de datos en lí­nea de herbarios extranjeros y colectas de campo. Se registraron 19 especies de encinos en Alta Verapaz, Baja Verapaz y Petén, nueve especies más de las reportadas previamente, actualizándose los rangos de distribución departamental de 18 especies a excepción de Quercus sapotifolia Liebm. De las especies registradas, 16 se encuentran con algún grado de amenaza, según el Listado de Especies Amenazadas y listas rojas de UICN. También se identificaron vací­os de información acerca de la distribución de estas especies dentro de remanentes boscosos importantes en los departamentos evaluados. Se espera que a partir de este estudio se incrementen los esfuerzos por comprenden la riqueza y distribución de las especies de encino para Guatemala