Majorana vs Pseudo-Dirac Neutrinos at the ILC

Neutrino masses could originate in seesaw models testable at colliders, with light mediators and an approximate lepton number symmetry. The minimal model of this type contains two quasi-degenerate Majorana fermions forming a pseudo-Dirac pair. An important question is to what extent future colliders will have sensitivity to the splitting between the Majorana components, since this quantity signals the breaking of lepton number and is connected to the light neutrino masses. We consider the production of these neutral heavy leptons at the ILC, where their displaced decays provide a golden signal: a forward-backward charge asymmetry, which depends crucially on the mass splitting between the two Majorana components. We show that this observable can constrain the mass splitting to values much lower than current bounds from neutrinoless double beta decay and natural loop corrections.Comment: 16 pages, 5 figures; v2: Minor changes, version accepted for publication in EPJ

Can SUSY relax LNV constraints coming from loop corrections to light neutrino masses on the low-scale Seesaw?

Heavy neutrinos from the Type-I Seesaw model can have a large mixing with active states, motivating their search at collider experiments. However, loop corrections to light neutrino masses constrain the heavy neutrinos to appear in pseudo-Dirac pairs, leading to a potential suppression of lepton number violating parameters. In this work we perform a detailed review of a proposal to relax constraints on lepton number violation by adding supersymmetry. We define the conditions necessary to maximise the SUSY screening effect, with the objective of allowing a larger mass splitting between low-scale heavy neutrino masses. We find that the sole addition of SUSY does not guarantee a screening, and that favourable cases have some degree of fine-tuning.Comment: 10 figure

Search for Long-Lived Heavy Neutrinos at the LHC with a VBF Trigger

The charged current production of long-lived heavy neutrinos at the LHC can use a prompt charged lepton for triggering the measurement of the process. However, in order to fully characterize the heavy neutrino interactions, it is necessary to also probe Higgs or $Z$ mediated neutral current production. In this case the charged lepton is not available, so other means of triggering are required. In this work, we explore the possibility of using a vector boson fusion trigger in the context of a GeV-scale Type I Seesaw model. We consider a minimal model, where both Higgs and Z-mediated contributions produce one heavy neutrino, as well as an extended model where the Higgs can decay into two heavy ones. Both scenarios are tested through displaced dilepton and displaced multitrack jet searches.Comment: 31 pages, 1 appendix, 5 figures; v2: improved version, accepted for publication in EPJ

Electric dipole moments from spontaneous CP violation in SU(3)-flavoured SUSY

The SUSY flavour problem is deeply related to the origin of flavour and hence to the origin of the SM Yukawa couplings themselves. Since all CP-violation in the SM is restricted to the flavour sector, it is possible that the SUSY CP problem is related to the origin of flavour as well. In this work, we present three variations of an SU(3) flavour model with spontaneous CP violation. Such models explain the hierarchy in the fermion masses and mixings, and predict the structure of the flavoured soft SUSY breaking terms. In such a situation, both SUSY flavour and CP problems do not exist. We use electric dipole moments and lepton flavour violation processes to distinguish between these models, and place constraints on the SUSY parameter space.Comment: 8 pages, 2 Figures, to appear in the DISCRETE'08 proceeding

Magneto--thermal evolution of neutron stars

We study the mutual influence of thermal and magnetic evolution in a neutron star's crust in axial symmetry. Taking into account realistic microphysical inputs, we find the heat released by Joule effect consistent with the circulation of currents in the crust, and we incorporate its effects in 2D cooling calculations. We solve the induction equation numerically using a hybrid method (spectral in angles, but a finite--differences scheme in the radial direction), coupled to the thermal diffusion equation. We present the first long term 2D simulations of the coupled magneto-thermal evolution of neutron stars. This substantially improves previous works in which a very crude approximation in at least one of the parts (thermal or magnetic diffusion) has been adopted. Our results show that the feedback between Joule heating and magnetic diffusion is strong, resulting in a faster dissipation of the stronger fields during the first million years of a NS's life. As a consequence, all neutron stars born with fields larger than a critical value (about 5 10^13 G) reach similar field strengths (approximately 2-3 10^{13} G) at late times. Irrespectively of the initial magnetic field strength, after $10^6$ years the temperature becomes so low that the magnetic diffusion timescale becomes longer than the typical ages of radio--pulsars, thus resulting in apparently no dissipation of the field in old NS. We also confirm the strong correlation between the magnetic field and the surface temperature of relatively young NSs discussed in preliminary works. The effective temperature of models with strong internal toroidal components are systematically higher than those of models with purely poloidal fields, due to the additional energy reservoir stored in the toroidal field that is gradually released as the field dissipates.Comment: 10 pages, 5 figures, accepted for publication in A&

On the sensitivity reach of LQ production with preferential couplings to third generation fermions at the LHC

Leptoquarks (LQs) are hypothetical particles that appear in various extensions of the Standard Model (SM) that can explain observed differences between SM theory predictions and experimental results. The production of these particles has been widely studied at various experiments, most recently at the Large Hadron Collider (LHC), and stringent bounds have been placed on their masses and couplings, assuming the simplest beyond-SM (BSM) hypotheses. However, the limits are significantly weaker for LQ models with family non-universal couplings containing enhanced couplings to third-generation fermions. We present a new study on the production of a LQ at the LHC, with preferential couplings to third-generation fermions, considering proton-proton collisions at $\sqrt{s} = 13$ $\mathrm{TeV}$ and $\sqrt{s} = 13.6$ $\mathrm{TeV}$. Such a hypothesis is well motivated theoretically and it can explain the recent anomalies in the precision measurements of $\mathrm{B}$-meson decay rates, specifically the $R_{D^{(*)}}$ ratios. Under a simplified model where the LQ masses and couplings are free parameters, we focus on cases where the LQ decays to a $\tau$ lepton and a $\mathrm{b}$ quark, and study how the results are affected by different assumptions about chiral currents and interference effects with other BSM processes with the same final states, such as diagrams with a heavy vector boson, $\mathrm{Z}^{'}$. The analysis is performed using machine learning techniques, resulting in an increased discovery reach at the LHC and allowing us to probe the entirety of the new physics phase space which addresses the $\mathrm{B}$-meson anomalies, for LQ masses up to 2.25 $\mathrm{TeV}$.Comment: 26 pages, 13 figure

Dumping inflaton energy density out of this world

We argue that a brane world with a warped, infinite extra dimension allows for the inflaton to decay into the bulk so that after inflation, the effective dark energy disappears from our brane. This is achieved by the redshifting of the decay products into infinity of the 5th dimension. As a consequence, all matter and CMB density perturbations could have their origin in the decay of a MSSM flat direction rather than the inflaton. We also discuss a string theoretical model where reheating after inflation may not affect the observable brane.Comment: 16 page

Benchmark low-mass objects in Moving Groups

This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.In order to compile a sample of ultracool dwarfs that will serve as benchmarks for testing theoretical formation and evolutionary models, we selected low-mass cool (>M7) objects that are potentially members of five known young Moving Groups in the solar neighbourhood. We have studied the kinematics of the sample, finding that 49 targets belong to the young disk area, from which 36 are kinematic member of one of the five moving groups under study. Some of the identified low-mass members have been spectroscopically characterised (T-eff, log g) and confirmed as young members through a detailed study of age indicators

The OTELO survey. A case study of [O III]4959,5007 emitters at <z> = 0.83

The OTELO survey is a very deep, blind exploration of a selected region of the Extended Groth Strip and is designed for finding emission-line sources (ELSs). The survey design, observations, data reduction, astrometry, and photometry, as well as the correlation with ancillary data used to obtain a final catalogue, including photo-z estimates and a preliminary selection of ELS, were described in a previous contribution. Here, we aim to determine the main properties and luminosity function (LF) of the [O III] ELS sample of OTELO as a scientific demonstration of its capabilities, advantages, and complementarity with respect to other surveys. The selection and analysis procedures of ELS candidates obtained using tunable filter (TF) pseudo-spectra are described. We performed simulations in the parameter space of the survey to obtain emission-line detection probabilities. Relevant characteristics of [O III] emitters and the LF([O III]), including the main selection biases and uncertainties, are presented. A total of 184 sources were confirmed as [O III] emitters at a mean redshift z=0.83. The minimum detectable line flux and equivalent width (EW) in this ELS sample are $\sim$5 $\times$ 10$^{-19}$ erg s$^{-1}$ cm$^{2}$ and $\sim$6 \AA, respectively. We are able to constrain the faint-end slope ($\alpha = -1.03\pm0.08$) of the observed LF([O III]) at z=0.83. This LF reaches values that are approximately ten times lower than those from other surveys. The vast majority (84\%) of the morphologically classified [O III] ELSs are disc-like sources, and 87\% of this sample is comprised of galaxies with stellar masses of M$_\star$ $<$ 10$^{10}$ M$_{\odot}$.Comment: v1: 16 pages, 6 figures. Accepted in Astronomy \& Astrophysics. v2: Author added in metadat

Symptoms and severity of visual stress in nursing students: implications for education and healthcare settings

Visual Stress reportedly affects 5-12% of the general population and 20-30% of people with dyslexia. Symptoms are characterized by visual discomfort and perceptual distortions when viewing lines of text, and can be exacerbated by fluorescent lighting and bright paper. In this study, nursing students reported their levels of visual discomfort while reading text on contemporary (ultra-white) paper and on beige-coloured paper, under either standard classroom-lighting (600 lux; n = 31) or reduced illumination(400 lux; n = 25). Under the standard lighting, 10(28%) of subjects reported notable levels of Visual Stress (scoring ≥15 on a visual discomfort scale of 1-30). When reading from the beige-coloured paper the group reported less discomfort across all six symptoms. These differences were statistically significant for five of the six symptoms and the total discomfort score. The results were similar but less pronounced for the group in the reduced illumination condition. This study found that Visual Stress-related reading discomfort can also affect capable readers and, moreover, that simple adjustments to lighting and/or visual media can alleviate such symptoms. The implications of these findings for organisational practice in education and healthcare settings are discussed. El estrés visual puede afectar del 5 al 12% de la población general y del 20 al 30% de las personas con dislexia. Los síntomas se caracterizan por incomodidad visual y distorsiones de la percepción visual en la lectura, y pueden agravarse con la iluminación fluorescente y el papel brillante. En este estudio, estudiantes de enfermería expresan niveles de incomodidad visual al leer texto en papel ultrablanco y en papel de color beige, ya sea con iluminación estándar del aula (600 lux; n = 31) o con iluminación reducida (400 lux ; n = 25). Bajo la iluminación estándar, 10 (28%) de los sujetos informaron niveles notables de estrés visual (puntuación ? 15 en una escala de1 a 30). Al leer en color beige, el grupo presentó menos malestar en los síntomas. Estas diferencias fueron estadísticamente significativas para cinco síntomas y el total de malestar. Los resultados fueron menos pronunciados para el grupo en la condición de iluminación reducida. Encontrándose que la incomodidad de lectura relacionada con estrés visual también puede afectar a lectores expertos y, además, que simples ajustes a la iluminación y/o medios visuales pueden reducirla. Se discuten las implicaciones para la práctica en entornos educativos y sanitarios