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キーワード:
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要旨:
High energy neutrino telescopes are expected to play a major role in the discovery of the first unambiguous sources of cosmic-rays. With completion in 2011, the IceCube neutrino detector constitutes the most sensitive instrument to sources of high energy neutrinos. Its performance and discovery potential are usually given in the energy range above a few TeV, in order to achieve the best signal to noise for sources following an E^-2 spectrum without an energy cutoff up to at least 1 PeV. However, given the present understanding and multiwavelength picture of our galaxy, we can expect that galactic sources of high energy neutrinos show significant deviations from the E^-2, no cutoff approximation. The common data analysis are therefore not optimal for such galactic scenarios, requiring exposure times of the order of several years, even a decade, to reach a level of sensitivity at which a possible detection starts to be plausible. The main goal of this thesis is to improve the discovery potential of IceCube to galactic sources of high energy neutrinos, aiming to a better understanding of the high energy processes taking place in our galaxy. In order to fulfill this goal, I follow two lines of action: (1) to increase the detection capabilities of IceCube for neutrinos in the energy range between 100 GeV < E < 1 TeV; and (2) to develop a search method which is able to reduce the minimum detectable flux per point source. The improvement of the IceCube performance at energies below 1 TeV is achieved with the use of the combined detector configuration IceCube 22 strings plus AMANDA (Antarctic Muon And Neutrino Detector Array). The data processing scheme is designed in order to keep as many good low energy events as possible. As a result, this analysis achieved the best sensitivity for sources with neutrino spectra steeper than E^-2 and/or an energy cutoff below 1 PeV. The second goal of this thesis is motivated in order to search efficiently for high energy neutrinos from the Cygnus star forming region of the Galaxy. In order to extend the search beyond a single point source, I developed a method based on two-point analysis to detect, within an extended region, event patterns which might go undetected in conventional point source analysis. The results obtained with this method indicate that the minimum detectable flux per point source is reduced by 26%-59% with respect to standard point source analysis, provided there is more than one point source within the region under study. This method was applied on the Cygnus region of the Galaxy using the data sample obtained with the combined detector IceCube 22 strings plus AMANDA, yielding a significance of 2.3-sigma.
