89 research outputs found
From AMANDA to IceCube
No full textThe success of the AMANDA neutrino telescope has shown that the ice sheet at the geographical South Pole is a suitable medium for optical Cherenkov detection of high energy neutrino interactions. Several thousands of atmospheric neutrinos have been recorded by AMANDA and the sensitivity for cosmic neutrinos has continuously improved. So far no cosmic neutrino signals have been detected. The deployment of the much larger and more sensitive IceCube neutrino observatory has started and nine out of 80 strings have been installed. This paper summarizes some of the results obtained by the AMANDA telescope and presents the status of the IceCube project
A Dark Matter Search with AMANDA [Elektronisk resurs] : Limits on the Muon Flux from Neutralino Annihilations at the Centre of the Earth with 1997-99 Data
No full textThe nature of the dark matter in the Universe is one of the greatest mysteries in modern astronomy. The neutralino is a nonbaryonic dark matter candidate in minimal supersymmetric extensions to the standard model of particle physics. If the dark matter halo of our galaxy is made up of neutralinos some would become gravitationally trapped inside massive bodies like the Earth. Their pair-wise annihilation produces neutrinos that can be detected by neutrino experiments looking in the direction of the centre of the Earth.The AMANDA neutrino telescope, currently the largest in the world, consists of an array of light detectors buried deep in the Antarctic glacier at the geographical South Pole. The extremely transparent ice acts as a Cherenkov medium for muons passing the array and using the timing information of detected photons it is possible to reconstruct the muon direction.A search has been performed for nearly vertically upgoing neutrino induced muons with AMANDA-B10 data taken over the three year period 1997-99. No excess above the atmospheric neutrino background expectation was found. Upper limits at the 90 % confidence level has been set on the annihilation rate of neutralinos at the centre of the Earth and on the muon flux induced by neutrinos created by the annihilation products.</p
Serch for Neutralino Dark Matter with the AMANDA-II Neutrino Telescope [Elektronisk resurs]
No full textThe annihilation of weakly interacting massive particles (WIMPs), accumulated in gravitational potentials (e.g., the core of the Earth, the Sun or the Galactic halo) would lead to neutrino production. This thesis investigates the possibility of searching for WIMPs in the form of the lightest supersymmetric particle (neutralino) trapped in the Sun using the AMANDA-II neutrino telescope. AMANDA-II is a large Cherenkov detector located deep in the ice at the geographical South Pole. The presented work is based on data taken during the year 2001. An analysis optimized to search for the neutralino-induced flux from the Sun has been developed. The observation of no excess with respect to the expected atmospheric neutrino background has been interpreted as an upper limit on the neutralino annihilation rate in the Sun and on the neutralino-induced muon flux in the vicinity of the detector.</p
Åtta frågor om socialarbetaren och det sociala arbetet
No full textNär vi planerade detta temanummer blev vi snart på det klara med att vi ville ha med praktiskt verksamma förtroendemäns och socialarbetares syn på socialarbetarrollen och det sociala arbetets innehåll. Vi uppmanade därför ett par socialarbetare och politiker att ge en personlig beskrivning av det sociala arbetets vardag, förhoppningar inför framtiden etc. Dessutom formulerade vi åtta frågor kring temat "Socialarbetaren och det sociala arbetet" och bad ett antal personer verksamma inom olika delar av det sociala arbetsfältet att besvara frågorna. Vi fick så småningom svar från tio av totalt fjorton vidtalade. Vi publicerar här svaren med vissa klar görande kommentarer.Följande personer ingick i vår panel: 1 Eva Ahlander, skolkurator i Sundsvall2 Lars Berg, föreståndare för Drevvikens ungdomshem3 Bengt Börjesson, forskare och chef på Barnbyn Skå4 Familjerådgivare vid familjerådgivningsbyrån Hornsgatan 52, Stockholm (genom Ann-Mari Engstedt)5 Mats Forsberg, socialchef i Eskilstuna6 Per Olof Henriksson, socialinspektör i Härnösand7 Mats Hulth (s). socialborgarråd i Stockholm8 Kjell Jansson, sekreterare vid Stockholms socialförvaltnings planeringsavdelning9 Birgitta Jonsson (kds), ledamot av sociala centralnämnden i Vilhelmina10 Peter Lamming, socialarbetare vid en social servicecentral i Stockholm
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Observation of Anisotropy in the Arrival Directions of Galactic Cosmic Rays at Multiple Angular Scales with IceCube
No full textBetween 2009 May and 2010 May, the IceCube neutrino detector at the South Pole recorded 32 billion muons generated in air showers produced by cosmic rays with a median energy of 20 TeV. With a data set of this size, it is possible to probe the southern sky for per-mil anisotropy on all angular scales in the arrival direction distribution of cosmic rays. Applying a power spectrum analysis to the relative intensity map of the cosmic ray flux in the southern hemisphere, we show that the arrival direction distribution is not isotropic, but shows significant structure on several angular scales. In addition to previously reported large-scale structure in the form of a strong dipole and quadrupole, the data show small-scale structure on scales between 15 degrees and 30 degrees. The skymap exhibits several localized regions of significant excess and deficit in cosmic ray intensity. The relative intensity of the smaller-scale structures is about a factor of five weaker than that of the dipole and quadrupole structure. The most significant structure, an excess localized at (right ascension alpha = 122 degrees.4 and declination d = -47 degrees.4), extends over at least 20 degrees in right ascension and has a post-trials significance of 5.3 sigma. The origin of this anisotropy is still unknown.</p
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