[1] Ist Nazl Fis Nucl, Sez Napoli, I-80125 Naples, Italy
[2] Univ Naples Federico II, Naples, Italy
[3] Univ Salerno, Fisciano, SA, Italy
[4] Ist Nazl Fis Nucl, Sez Perugia, I-06100 Perugia, Italy
[5] Univ Perugia, I-06100 Perugia, Italy
[6] Ist Nazl Fis Nucl, Sez Pisa, Pisa, Italy
[7] Univ Pisa, I-56100 Pisa, Italy
[8] Ist Nazl Fis Nucl, Sez Rome, Rome, Italy
[9] Univ Roma La Sapienza, Rome, Italy
[10] Observ Cote Azur, Dept Artemis, F-06304 Nice 4, France
[11] Ist Nazl Fis Nucl, Lab Nazl Frascati, I-00044 Frascati, Rm, Italy
[12] EGO, Cascina, PI, Italy
[13] Univ Paris 11, CNRS, IN2P3, LAL, F-91405 Orsay, France
[14] NIKHEF, NL-1009 DB Amsterdam, Netherlands
[15] Vrije Univ Amsterdam, NL-1081 HV Amsterdam, Netherlands
[16] Univ Savoie, CNRS, IN2P3, LAPP, Annecy Le Vieux, France
[17] ESPCI, Paris, France
[18] Ist Nazl Fis Nucl, Sez Firenze Urbino, Sesto Fiorentino, Italy
[19] Univ Florence, I-50121 Florence, Italy
[20] Univ Urbino, I-61029 Urbino, Italy
[21] LMA, Lyon, France