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High-energy cosmic neutrinos astronomy using a Mediterranean undersea telescope

Final Report Summary - NEUTEL-APC (High-energy cosmic neutrinos astronomy using a Mediterranean undersea telescope)

The observation of high-energy cosmic neutrinos produced in distant astrophysical accelerators has become one of the major challenges of today's astroparticle physics, motivated by the possibility to open a new observational window on the distant Universe. The NEUTEL-APC project is a contribution to the experimental effort of the European scientific community in operating a prototype undersea neutrino telescope in the Mediterranean: ANTARES (http://antares.in2p3.fr) , deployed at ~2500 m depth off the shore of Toulon (France). The main goal of the project is to exploit at best the technological and scientific potentialities of this detector, with a view on the larger-scale project in the Mediterranean under study within the KM3NeT Consortium (http://www.km3net.org). NEUTEL-APC was carried out at the Astroparticle Physics and Cosmology (APC) institute of the University Paris 7 Denis Diderot. It was subdivided into 3 main tasks:

1. Understanding the detector
The deployment of the ANTARES telescope was achieved in May 2008, just before this project started, and this task concerned technical aspects related to the study of the response of the detector elements, i.e. photomultipliers (PMTs) enclosed in pressure-proof optical modules (OMs), in a deep-sea environment characterized by specific optical backgrounds. An important contribution of the project has been the development at APC, in collaboration with photodetection experts, of a black-box test bench for the study of the response of the ANTARES PMTs in conditions of illumination that mimic their deep-sea environment. It relies on two innovative aspects: an APC-patented calibrated light source, and a motorized device allowing a scanning of the OM surface with variable incidence angles of the light source (see fig. 1). The two measurement campaigns performed to date concerned a characterization of the afterpulses and a detailed mapping of the detection efficiency of several OMs to evaluate their acceptance to photons incident at different angles (see e.g. fig.2). The unprecedented precision of these measurements will contribute to improve the quality of the OM simulation and hence the performance of reconstruction algorithms. This bench will also be used in the future for a detailed characterization of the prototype optical modules for the next-generation detector KM3NeT.

2. Optimizing the data taking and processing
The researcher has been appointed in July 2009 as Responsible for the Data Quality Task by the ANTARES Collaboration. This task aimed at developing tools to evaluate and control the quality of the data in order to maximize the amount of data exploitable for physical analyses. Its most important outcome is the development of a dedicated monitoring tool under the form of a Data Quality sql table embedded in the ANTARES database and thoroughly used within the collaboration. Besides allowing for the monitoring of external conditions and of the status of the detector (including trigger and reconstruction rates), it provides quality flags reflecting the suitability of given sets of data for different kinds of physics analyses.

3. Analyzing/interpreting the data

This task has contributed to the development in ANTARES of a novel multi-messenger analysis method: a joint search program for sources of high-energy neutrinos (HEN) and gravitational waves (GW), conducted in collaboration with physicists from the major operating GW experiments: VIRGO (also represented at APC) and LIGO. The researcher took active part in the set up of a common "GWHEN" working group, whose activities are now regulated by a MoU signed by the 3 collaborations in Feb. 2010. The results of the first joint ANTARES-LIGO-VIRGO search, to be issued soon, are expected to provide new insights on the conditions of emission from common astrophysical sources.