[1] Univ Roma Tor Vergata, Dipartimento Fis, Via Ric Sci 1, I-00133 Rome, Italy
[2] Ist Nazl Fis Nucl, Sez Rome Tor Vergata, I-00133 Rome, Italy
[3] Univ Virginia, Dept Phys, Charlottesville, VA 22901 USA
[4] Univ South Carolina, Dept Phys, Columbia, SC 29208 USA
[5] Ohio Univ, Dept Phys, Athens, OH 45701 USA
[6] Univ Catania, Dept Fis, I-95123 Catania, Italy
[7] Ist Nazl Fis Nucl, Lab Naz Sud, I-95123 Catania, Italy
[8] Virginia Polytech Inst & State Univ, Dept Phys, Blacksburg, VA 24061 USA
[9] IN2P3, Lab Phys Subatomique Cosmol, F-38026 Grenoble, France
[10] ENEA CR Casaccia, I-00060 Rome, Italy
[11] Dept Phys, Brookhaven Natl Lab, Upton, NY 11973 USA
[12] Univ Genoa, Dept Fis, I-16146 Genoa, Italy
[13] Univ Bern, LHEP, Albert Einstein Ctr Fundamantal Phys, Bern, Switzerland
[14] Univ Turin & INFN Sezione Torino, Dept Fis Sperimentale, I-10125 Turin, Italy
[15] Ist Superiore Sanita, I-00185 Rome, Italy
[16] Univ Messina, Dipartimento Fis, I-98166 Messina, Italy
[17] Ist Nazl Fis Nucl Sezione Catania, I-95123 Catania, Italy
[18] Forschungszentrum Julich GmbH, D-52425 Julich, Germany
[19] Syracuse Univ, Dept Phys, Syracuse, NY 13210 USA
[20] Thomas Jefferson Nat Accelerator Fac, Newport News, VA 23606 USA
[21] Norfolk St Univ, Newport News, VA 23606 USA
[22] Nucl Res Inst, Moscow RU-117312, Russia
[23] Ist Nazl Fis Nucl, Nazl Frascati Lab, I-00044 Frascati, Italy
[24] James Madison Univ, Harrisonburg, VA 22807 USA