[1] Ist Nazl Fis Nucl, Sez Napoli, Fisciano, Italy
[2] Univ Naples Federico II, Complesso Univ Monte S Angelo, Fisciano, Italy
[3] Univ Salerno, Fisciano, Italy
[4] Univ Salerno, Perugia, Italy
[5] Ist Nazl Fis Nucl, Sez Perugia, I-06100 Perugia, Italy
[6] Univ Perugia, I-06100 Perugia, Italy
[7] Ist Nazl Fis Nucl, Sez Pisa, Pisa, Italy
[8] Univ Pisa, Pisa, Italy
[9] Observ Cote Azur, Dept Artemis, F-06304 Nice, France
[10] Ist Nazl Fis Nucl, Lab Nazl Frascati, I-00044 Frascati, Italy
[11] EGO, Cascina, Italy
[12] Univ Paris 11, CNRS, Lab Accelerateur Lineaire, IN2P3, Orsay, France
[13] Lab Annecy Le Vieux Phys Particules, F-74941 Annecy Le Vieux, France
[14] ESPCI, F-75005 Paris, France
[15] Ist Nazl Fis Nucl, Sez Roma, Rome, Italy
[16] Univ Roma La Sapienza, Rome, Italy
[17] Ist Nazl Fis Nucl, Sez Firenze Urbino, Sesto Fiorentino, Italy
[18] Univ Florence, Florence, Italy
[19] Osserv Astrofis Arcetri, I-50125 Florence, Italy
[20] Univ Urbino, I-61029 Urbino, Italy
[21] LMA, Lyon, France