Search of Neutralino Dark Matter with the ANTARES Neutrino Telescope

The work presented in this thesis, developed in the framework of the ANTARES experiment, aims at evaluating the performance of the detector in the low energy region (10 GeV-5 TeV) where signals from neutralino DM annihilation are expected. To make an immediate comparison with other present and future neutrino telescopes, the effective area as a function of the incident neutrino energy has been computed taking into account the effect of different conditions of continuous random background rate and assessing the efficiency of trigger and reconstruction algorithms. In the framework of mSUGRA SUSY theories, we have used this information to calculate the ANTARES sensitivity to signals from neutralino Dark Matter annihilation. Through a MonteCarlo simulation of the full 12-line detector, the effective area as a function of the neutralino mass has been evaluated in the case of soft and hard annihilation. We have thus overcome the problem of scanning the 5-dimensional mSUGRA parameter space and have achieved modelindependent results for the effective area. We have then computed the upper limit that can be set on the neutrino flux from neutralino annihilation after one year of data taking with the full detector. The very same study has been carried out to provide a preliminary estimate of the performance of a km3 scale detector. Three geometries differing in the spatial distribution and orientation of the PMTs have been simulated and the corresponding effective area as function of the neutralino mass have been computed to establish the achievable neutrino flux upper limit. Beyond the simulation work, the analysis of the data collected in 2007 with the partially completed ANTARES detector (5 lines out of 12) has been carried out: the runs taken at low levels of background rate (golden runs) have been selected to establish an experimental upper limit on a neutralino induced neutrino flux using the Feldman and Cousins approach. After the evaluation of the effective area of the 5-line detector, the upper limit on the neutrino flux has been converted into an upper limit on the muon flux, achieving a close result to a recently preliminary AMANDA measurement, despite the fact that the data taking period of ANTARES golden runs was only about 1/10 of a year and that the detector was only almost half completed. This consideration bring us to underline that significant improvements of the results here presented can be achieved with the analysis of more, possibly full-detector, data. The simulation of the 12-line detector already tells us that we could establish an upper limit on the neutrino flux about two order of magnitude better. As far as the km3 studies are concerned, possible improvements include the study of optimised trigger algorithms, of the corresponding effect on the effective area and on the resulting upper limits on the neutrino flux.