[1] Univ Edinburgh, Dept Phys & Astron, Edinburgh EH9 3JZ, Midlothian, Scotland
[2] Univ Catania, Dipartimento Fis, I-95129 Catania, Italy
[3] Ist Nazl Fis Nucl, Lab Nazl Sud, I-95123 Catania, Italy
[4] Ist Nazl Fis Nucl, Sez Catania, I-95129 Catania, Italy
[5] Catholic Univ Louvain, Inst Phys Nucl, Ctr Rech Cyclotron, B-1348 Louvain, Belgium
[6] Univ Budapest, Dept Phys, Budapest, Hungary