Getting just the Supersymmetric Standard Model at Intersecting Branes on the Z6-orientifold

In this paper, globally N=1 supersymmetric configurations of intersecting D6-branes on the Z6-orientifold are discussed, involving also fractional branes. It turns out rather miraculously that one is led almost automatically to just ONE particular class of 5 stack models containing the SM gauge group, which all have the same chiral spectrum. The further discussion shows that these models can be understood as exactly the supersymmetric standard model without any exotic chiral symmetric/antisymmetric matter. The superpartner of the Higgs finds a natural explanation and the hypercharge remains massless. However, the non-chiral spectrum within the model class is very different and does not in all cases allow for a N=2 low energy field theoretical understanding of the necessary breaking U(1)xU(1)->U(1) along the Higgs branch, which is needed in order to get the standard Yukawa couplings. Also the left-right symmetric models belong to exactly one class of chiral spectra, where the two kinds of exotic chiral fields can have the interpretation of forming a composite Higgs. The aesthetical beauty of these models, involving only non-vanishing intersection numbers of an absolute value three, seems to be unescapable.Comment: 45 pages, 2 figures, v3:some signs corrected in erratum, conclusions unchange

The ALTEA experiment onboard the International Space Station

The knowledge of the composition of the radiation environment is an important information for all the radiation safety issues needed for the planning of future long manned space missions. The ALTEA detector is on board the International Space Station since July 2006 and during this period it has performed a detailed measurement of the radiation environment. In this paper we present a summary of past measures and results

Solar particle event detected by ALTEA on board the International Space Station

Context. Solar activity poses substantial risk for astronauts of the International Space Station (ISS) both on board and during extravehicular activity. An accurate assessment of the charged radiation flux in space habitats is necessary to determine the risk and the specific type of radiation exposure of ISS crew members, and to develop ways to protect future crews for planetary missions, even in case of high solar activity. Aims. To reduce the present-day uncertainties about the nature and magnitude of the particle fluxes in space habitats during a solar event, it is fundamental to measure those fluxes in situ. Methods. The ALTEA (Anomalous Long Term Effects on Astronauts) experiment on board the ISS is an active detector composed of six silicon telescopes and is able to follow the dynamics of the radiation flux. During its operation in 2012 a number of flux peaks were detected in correspondence with solar events. Results. We present in this work an analysis of the ALTEA data measured during the March 7th, 2012 solar event, produced by NOAA AR11429. Conclusions. During this event, the flux was enhanced tenfold with respect to ‘‘quiet Sun’’ conditions, producing strong dose increases at high geomagnetic latitudes

The relativistic solar particle event of May 17th, 2012 observed on board the International Space Station

High-energy charged particles represent a severe radiation risk for astronauts and spacecrafts and could damage ground critical infrastructures related to space services. Different natural sources are the origin of these particles, among them galactic cosmic rays, solar energetic particles and particles trapped in radiation belts. Solar particle events (SPE) consist in the emission of high-energy protons, alpha-particles, electrons and heavier particles from solar flares or shocks driven by solar plasma propagating through the corona and interplanetary space. Ground-level enhancements (GLE) are rare solar events in which particles are accelerated to near relativistic energies and affect space and ground-based infrastructures. During the current solar cycle 24 a single GLE event was recorded on May 17th, 2012 associated with an M5.1-class solar flare. The investigation of such a special class of solar events permits us to measure conditions in space critical to both scientific and operational research. This event, classified as GLE71, was detected on board the International Space Station (ISS) by the active particle detectors of the ALTEA (Anomalous Long Term Effects in Astronauts) experiment. The collected data permit us to study the radiation environment inside the ISS. In this work we present the first results of the analysis of data acquired by ALTEA detectors during GLE71 associated with an M5.1-class solar flare. We estimate the energy loss spectrum of the solar particles and evaluate the contribution to the total exposure of ISS astronauts to solar high-energy charged particles

Solar particle event detected by ALTEA on board the International Space Station

Context. Solar activity poses substantial risk for astronauts of the International Space Station (ISS) both on board and during extravehicular activity. An accurate assessment of the charged radiation flux in space habitats is necessary to determine the risk and the specific type of radiation exposure of ISS crew members, and to develop ways to protect future crews for planetary missions, even in case of high solar activity. Aims. To reduce the present-day uncertainties about the nature and magnitude of the particle fluxes in space habitats during a solar event, it is fundamental to measure those fluxes in situ. Methods. The ALTEA (Anomalous Long Term Effects on Astronauts) experiment on board the ISS is an active detector composed of six silicon telescopes and is able to follow the dynamics of the radiation flux. During its operation in 2012 a number of flux peaks were detected in correspondence with solar events. Results. We present in this work an analysis of the ALTEA data measured during the March 7th, 2012 solar event, produced by NOAA AR11429. Conclusions. During this event, the flux was enhanced tenfold with respect to ‘‘quiet Sun’’ conditions, producing strong dose increases at high geomagnetic latitudes