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Issue Date: 20-Dec-2018
Authors: Ferrara, Giovanna
Title: Search for neutrino counterparts of the HAWC point-source sky map using 10 years of ANTARES data and KM3NeT first results
Abstract: The ANTARES detector is the largest neutrino telescope in the norther hemisphere in operation since 2007, with the main scientific goal to discover astrophysical neutrino sources in the TeV-PeV energy range. In this thesis the first results of the search for a neutrino counterpart of the HAWC gamma-ray sky using the data collected by the ANTARES telescope in the period of time 2007-2017 is presented. In particular the search for a neutrino emission from the point-like sources Markarian 421 and Markarian 501 and from the HAWC gamma-ray sky has been performed. At GeV-TeV energies the gamma-ray emission due to unresolved sources, resulting from the interaction of cosmic rays with matter and photons, is the dominant component of the gamma-ray sky. In consequence of the cosmic ray interactions in our Galaxy, it is also expected that a significant component of the diffuse neutrino flux reaching the Earth has a galactic origin and can be directly related to the observed galactic gamma-rays. The sky maps used to develop the 2 years HAWC gamma-ray point source catalogue, that represents the most sensitive survey of the TeV sky at the present day, can be used to investigate the origin of the neutrino emission. In order to search for a neutrino counterpart to the HAWC gamma-ray sky, two gamma-ray point source sky maps have been considered as reference models to determine a topological and spectral energy distributions of the neutrino flux all over the sky. Even if only a fraction of the observed gamma-ray emission can be considered of hadronic origin, in this work a one-to-one correspondence between the gamma-ray and neutrino fluxes has been assumed. The sensitivity of the search for point-like neutrino sources has been estimated through MC simulations of neutrinos. The contribution to the background of atmospheric muons and atmospheric neutrinos has been also taken into account. The background from atmospheric muons has been rejected by selecting upward-going neutrino-induced tracks and applying cuts on the quality parameters of the track reconstruction algorithm. The estimator of the reconstructed energy has been used to reject atmospheric neutrinos. The search for a neutrino emission from the point-like sources has been performed using a maximum likelihood method. The search for a neutrino emission from Markarian 421 and Markarian 501 sets a sensitivity two orders of magnitude higher than the predicted neutrino fluxes. The search for an all-sky neutrino emission from the HAWC point source sky map sets an average upper limit which is a factor about 7 higher than the brightest source of the list. A less sensitive result of about 20 % has been found respect to previous ANTARES point-like source search. Since the discrepancy between the average upper limits is mainly due to the different MC productions considered in the two analyses, the differences between the MC productions are under investigations. The possibility to improve the sensitivity of the full-sky search through a stacking analysis of the point-like sources of the HAWC gamma-ray sky will be investigated in a future extension of this work. A better limit setting on the ANTARES sensitivity can be reached including also the contribution of shower-like events. Finally, a much more realistic neutrino production model will be also taken into account. To extend the ANTARES performances the KM3NeT collaboration started to build a research infrastructure in the Mediterranean Sea which will host a multi cubic kilometre scale neutrino telescope, the ARCA detector. In this thesis the software developed for the qualification and monitoring of the KM3NeT/ARCA data is presented. The analysis of the ARCA data provided the first measurement of the depth dependence of the coincidence rates induced by atmospheric muons with the two ARCA-DUs, proving also the high-performance of the ARCA detector.
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