A search for tau neutrino induced showers with the MAGIC telescopes is presented. The MAGIC telescopes located at an altitude of 2200 m a.s.l. in the Canary Island of La Palma, can point towards the ...horizon or a few degrees below across an azimuthal range of about 80°. This provides a possibility to search for air showers induced by tau leptons arising from interactions of tau neutrinos in the Earth crust or the surrounding ocean. In this paper we show how such air showers can be discriminated from the background of very inclined hadronic showers by using Monte Carlo simulations. Taking into account the orography of the site, the point source acceptance and the event rates expected have been calculated for a sample of generic neutrino fluxes from photo-hadronic interactions in AGNs. The analysis of about 30 h of data taken towards the sea leads to a 90% C.L. point source limit for tau neutrinos in the energy range from 1.0 × 1015 eV to 3.0 × 1018 eV of about Eντ2×ϕ(Eντ)<2.0×10−4 GeV cm−2 s−1 for an assumed power-law neutrino spectrum with spectral index γ=−2. However, with 300 h and in case of an optimistic neutrino flare model, limits of the level down to Eντ2×ϕ(Eντ)<8.4×10−6 GeV cm−2 s−1 can be expected.
Clusters of galaxies are the largest known gravitationally bound structures in the Universe, with masses around 1015 M⊙, most of it in the form of dark matter. The ground-based Imaging Atmospheric ...Cherenkov Telescope MAGIC made a deep survey of the Perseus cluster of galaxies using almost 400 h of data recorded between 2009 and 2017. This is the deepest observational campaign so far on a cluster of galaxies in the very high energy range. We search for gamma-ray signals from dark matter particles in the mass range between 200 GeV and 200 TeV decaying into standard model pairs. We apply an analysis optimized for the spectral and morphological features expected from dark matter decays and find no evidence of decaying dark matter. From this, we conclude that dark matter particles have a decay lifetime longer than ∼1026 s in all considered channels. Our results improve previous lower limits found by MAGIC and represent the strongest limits on decaying dark matter particles from ground-based gamma-ray instruments.
Extreme high-frequency-peaked BL Lac objects (EHBLs) are blazars that exhibit extremely energetic synchrotron emission. They also feature nonthermal gamma-ray emission whose peak lies in the very ...high-energy (VHE, E > 100 GeV) range, and in some sources exceeds 1 TeV: this is the case for hard-TeV EHBLs such as 1ES 0229+200. With the aim of increasing the EHBL population, 10 targets were observed with the MAGIC telescopes from 2010 to 2017, for a total of 265 hr of good-quality data. The data were complemented by coordinated Swift observations. The X-ray data analysis confirms that all but two sources are EHBLs. The sources show only a modest variability and a harder-when-brighter behavior, typical for this class of objects. At VHE gamma-rays, three new sources were detected and a hint of a signal was found for another new source. In each case, the intrinsic spectrum is compatible with the hypothesis of a hard-TeV nature of these EHBLs. The broadband spectral energy distributions (SEDs) of all sources are built and modeled in the framework of a single-zone, purely leptonic model. The VHE gamma-ray-detected sources were also interpreted with a spine-layer model and a proton synchrotron model. The three models provide a good description of the SEDs. However, the resulting parameters differ substantially in the three scenarios, in particular the magnetization parameter. This work presents the first mini catalog of VHE gamma-ray and multiwavelength observations of EHBLs.
In order to evaluate the benefit derived by conventional views in the initial diagnosis of fractures of the orbital walls, a clinical study was designed to compare the results of evaluations by plain ...films and coronal CT scans. The conventional Caldwell's and Waters' views will provide a fairly reliable result as to the presence of orbital fractures: orbital floor (anterior in 78%, posterior in 73%), medial orbital wall (anterior in 71%, posterior in 72%), and ethmoid-maxillary plate in 64%. False-negative diagnosis was seen at the anterior portion of the floor in 13%, at the anterior portion of the medial orbital wall in 7%, and at the ethmoid-maxillary plate in 11%. False-negative diagnosis was seen at the orbital floor (anterior in 9%, posterior in 10%), at the medial orbital wall (anterior in 21%, posterior in 29%), and at the ethmoid-maxillary plate in 21%. Our results agree well with those of the past reports.
The jacket material, Incoloy 908, of the superconducting coil for International Thermonuclear Experimental Reactor (ITER) has a possibility of fracture due to stress-accelerated grain boundary ...oxidation (SAGBO) in the region of tensile residual stress above 200 MPa. In order to avoid the SAGBO fracture, a depth dependence of the strain in the jacket sample was obtained from the (1 1 1) plane spacing measured with the neutron diffractometer, RESA, installed at JRR-3M in JAERI. A residual stress distribution was calculated from the strain. The result shows that the tensile residual stress exceeds 200 MPa of the SAGBO condition in some areas inside the jacket.
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