1. APC, UMR 7164 (CNRS, Université Paris 7 Denis Diderot, CEA, Observatoire de Paris), 10 rue Alice Domon et Léonie Duquet, 75205 Paris Cedex 13, France
2. Institute for Nuclear Research of the Russian Academy of Sciences, 60th October Anniversary Prospect 7a, 117312 Moscow, Russia