Etude du bruit de fond engendré par l'accélérateur PEP-II avec un anneau de cristaux de CsI(Na). Etude des oscillations des mesons B neutres avec le détecteur BaBar en utilisant les événements di-leptons

The ANTARES collaboration is building an undersea neutrino telescope off Toulon (Mediterranean sea) with effective area ~0.1 km^2. An extensive study of the site properties has been achieved together with software analysis in order to optimize the performance of the detector. Results are summarized here. An instrumented line, linked to shore for first time via an electro-optical cable, has been immersed late 1999. The preliminary results of this demonstrator line are reported.