[1] Ist Nazl Fis Nucl, Sezione Napoli, Rome, Italy
[2] Univ Salerno, Fisciano, SA, Italy
[3] Ist Nazl Fis Nucl, Sezione Pisa, Pisa, Italy
[4] Univ Pisa, Pisa, Italy
[5] Ist Nazl Fis Nucl, Sezione Perugia, Rome, Italy
[6] Univ Perugia, I-06100 Perugia, Italy
[7] Ist Nazl Fis Nucl, Sezione Roma, Rome, Italy
[8] Dept Artemis Observ Cote Dazur, F-06304 Nice 4, France
[9] Univ Naples Federico II, Complesso Univ Monte S Angelo, Naples, Italy
[10] Univ Savoie, Lab Annecy Le Vieux Phys Particules, IN2P3, CNRS, Annecy Le Vieux, France
[11] EGO, Cascina, PI, Italy
[12] Univ Paris 11, LAL, IN2P3, CNRS, Orsay, France
[13] Natl Inst Subatom Phys, NL-1009 DB Amsterdam, Netherlands
[14] ESPCI, F-75005 Paris, France
[15] Ist Nazl Fis Nucl, Sezione Firenze, Sesto Fiorentino, Italy
[16] Univ Urbino Carlo Bo, Urbino, Italy
[17] Univ Florence, Florence, Italy
[18] Ist Nazl Fis Nucl, Sezione Roma Tor Vergata, Rome, Italy
[19] Univ Roma Tor Vergata, Rome, Italy
[20] Univ Siena, I-53100 Siena, Italy
[21] Univ Aquila, I-67100 Laquila, Italy
[22] LMA, Lyon, France
[23] Univ Roma La Sapienza, Rome, Italy
[24] Scuola Normale Super Pisa, Pisa, Italy
[25] Vrije Univ Amsterdam, NL-1081 HV Amsterdam, Netherlands