The CAST experiment: status and perspectives

The status of the solar axion search with the CERN Axion Solar Telescope (CAST) will be discussed. Results from the first part of CAST phase II where the magnet bores were filled with 4He gas at variable pressure in order to scan axion masses up to 0.4 eV will be presented. From the absence of excess X-rays when the magnet was pointing to the Sun, we set a typical upper limit on the axion-photon coupling of g < 2.17 x 10^10 GeV$-1 at 95% CL for axion masses lower than 0.4 eV, the exact result depending on the pressure setting. Our search for axions with masses up to about 1.2 eV using 3He as a buffer gas is in progress in the second part of CAST phase II. Expectations for sensibilities will be given. Near future perspectives as well as more long term options for a new helioscope experiment will be evoked.Comment: Proceedings of Identification of Dark Matter 2010-IDM2010 conferenc

Characterization of microbulk detectors in argon- and neon-based mixtures

A recent Micromegas manufacturing technique, so called Microbulk, has been developed, improving the uniformity and stability of this kind of detectors. Excellent energy resolutions have been obtained, reaching values as low as 11% FWHM at 5.9 keV in Ar+5%iC4H10. This detector has other advantages like its flexible structure, low material budget and high radio-purity. Two microbulk detectors with gaps of 50 and 25 um have been characterized in argon- and neon-based mixtures with ethane, isobutane and cyclohexane. The results will be presented and discussed. The gain curves have been fitted to the Rose-Korff gain model and dependences of the electron mean free path and the threshold energy for ionization have been obtained. The possible relation between these two parameters and the energy resolution will be also discussed.Comment: Submitted to the Journal of Instrumentatio

Open string axions and the flavor problem

We consider extensions of the standard model inspired by intersecting D-brane constructions, in order to address flavor mass textures. We include additional anomalous gauge symmetries, and scalar fields to break them and to generate Froggatt-Nielsen mass terms. Green-Schwarz axions are included to cancel mixed anomalies rendering the models consistent. At low energies, a residual anomalous global symmetry remains, and its associated pseudo-Goldstone mode becomes the physical axion, which can be interpreted as an axion arising from open string modes. General considerations show that such axions are very common in D-brane models and can be completely incompatible with current bounds. Astrophysical constraints are placed on the axion both by including neutrino masses in the Froggatt-Nielsen scheme and considering QCD instanton contributions to the axion mass. We find simple models where the axion decay constant is in the allowed range, but only one such minimal model with this property is free from excessive fine tunings elsewhere. We also note that generically addressing flavor textures for the CKM matrix leads to deconstructed extra dimensions.Comment: 30 pages, 2 figures. v2: references added. v3:typos fixe

Track reconstruction with MIMAC

Directional detection of Dark Matter is a promising search strategy. However, to perform such kind of detection, the recoiling tracks have to be accurately reconstructed: direction, sense and position in the detector volume. In order to optimize the track reconstruction and to fully exploit the data from the MIMAC detector, we developed a likelihood method dedicated to the track reconstruction. This likelihood approach requires a full simulation of track measurements with MIMAC in order to compare real tracks to simulated ones. Finally, we found that the MIMAC detector should have the required performance to perform a competitive directional detection of Dark Matter.Comment: 9 pages, 6 figures; Proceedings of the 3rd International conference on Directional Detection of Dark Matter (CYGNUS 2011), Aussois, France, 8-10 June 201

Three-dimensional track reconstruction for directional Dark Matter detection

Directional detection of Dark Matter is a promising search strategy. However, to perform such detection, a given set of parameters has to be retrieved from the recoiling tracks : direction, sense and position in the detector volume. In order to optimize the track reconstruction and to fully exploit the data of forthcoming directional detectors, we present a likelihood method dedicated to 3D track reconstruction. This new analysis method is applied to the MIMAC detector. It requires a full simulation of track measurements in order to compare real tracks to simulated ones. We conclude that a good spatial resolution can be achieved, i.e. sub-mm in the anode plane and cm along the drift axis. This opens the possibility to perform a fiducialization of directional detectors. The angular resolution is shown to range between 20$^\circ$ to 80$^\circ$, depending on the recoil energy, which is however enough to achieve a high significance discovery of Dark Matter. On the contrary, we show that sense recognition capability of directional detectors depends strongly on the recoil energy and the drift distance, with small efficiency values (50%-70%). We suggest not to consider this information either for exclusion or discovery of Dark Matter for recoils below 100 keV and then to focus on axial directional data.Comment: 27 pages, 20 figure

Diseño, análisis y fabricación del soporte Front Wing y conjunto Front Wing del CAT13e

Durante la temporada 2018/2019 se diseñó un monoplaza Formula Student que técnicamente se consideró el más avanzado de la historia del equipo.Se implementaron muchas mejoras y cambios que a su vez introdujeron nuevos problemas y retos que el equipo tuvo que afrontar. Con el objetivo de mejorar el flujo del aire y el rendimiento del monoplaza CAT12e se rediseñó el soporte del conjunto front wing. El nuevo diseño y posicionamiento del soporte era favorable para el comportamiento aerodinámico del monoplaza pero creaba conflictos con el nuevo atenuador de impactos que se quería instalar en el monoplaza CAT13e. En la temporada 2019/2020 la intención era usar el mismo molde para fabricar el monocasco que la temporada anterior, con lo que no podría haber cambios significativos respecto a la geometría del monocasco. Para poder implementar un nuevo diseño de atenuador de impactos, respetar la normativa impuesta por la competición Formula Student Germany y mantener una geometría de monocasco y front wing se tendría que rediseñar el soporte del conjunto front wing. En este trabajo se documenta el proceso de diseñar un soporte de front wing que cumpla con la normativa, soporte los requisitos mecánicos generados por la carga aerodinámica y que el peso del soporte sea el mínimo posible. Además se analizará la estructura del conjunto front wing para garantizar que también soportará los requisitos mecánicos generados durante el uso del monoplaza durante la temporada 2019/2020. Para ello se utilizarán varios programas de diseño y simulación para poder encontrar el compromiso entre todos los objetivos anteriormente expuestos. Por desgracia la temporada del CAT13e se ha visto cancelada debido a la pandemia mundial del COVID 19 pero el diseño y aprendizaje del proceso de diseño del soporte se trasladarán a los futuros miembros del equipo que lo podrán usar para diseñar futuras mejoras en los futuros monoplazas