1. Centro Ricerche Enrico Fermi—Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi”, 00184 Roma, Italy
2. Laboratori Nazionali di Frascati, INFN, 00044 Frascati, Italy
3. IFIN-HH, Institutul National pentru Fizica si Inginerie Nucleara Horia Hulubei, 077125 Măgurele, Romania
4. Physics Department, “Sapienza” University of Rome, 00185 Rome, Italy
5. Stefan-Meyer-Institute for Subatomic Physics, Austrian Academy of Science, 1010 Wien, Austria
6. Physik Department E62, Technische Universität München, 85748 Garching, Germany
7. Laboratori Nazionali del Gran Sasso, INFN, 67100 L’Aquila, Italy
8. Atomic Institute, Technical University Vienna, 1020 Wien, Austria