[1] Ist Nazl Fis Nucl, Lab Nazl Frascati, I-00044 Frascati, Italy
[2] Ist Nazl Ottica, CNR, UOS Pisa, I-56124 Pisa, Italy
[3] Univ Messina, Dipartimento Fis & Sci Terra, Messina, Italy
[4] Ist Nazl Fis Nucl, GC Udine, Udine, Italy
[5] Ist Nazl Fis Nucl, Sez Napoli, Naples, Italy
[6] Ist Nazl Fis Nucl, Sez Roma Tor Vergata, Rome, Italy
[7] Univ Trieste, Trieste, Italy
[8] Univ Naples Federico II, Naples, Italy
[9] Univ Udine, I-33100 Udine, Italy
[10] Univ Cassino, I-03043 Cassino, Italy
[11] Univ Rijeka, Rijeka, Croatia
[12] Univ Washington, Seattle, WA 98195 USA