[1] Univ Roma Tre, Ist Nazl Fis Nucl, Rome, Italy
[2] Univ Roma Tre, Dipartimento Fis, Rome, Italy
[3] Univ Naples, Ist Nazl Fis Nucl, I-80138 Naples, Italy
[4] Univ Naples, Dipartimento Fis, I-80138 Naples, Italy
[5] Zhenghou Univ, Henan, Peoples R China
[6] Univ Lecce, Ist Nazl Fis Nucl, I-73100 Lecce, Italy
[7] Univ Lecce, Dipartimento Fis, I-73100 Lecce, Italy
[8] Shandong Univ, Jinan 250100, Peoples R China
[9] Univ Roma Tor Vergata, Ist Nazl Fis Nucl, I-00173 Rome, Italy
[10] Univ Roma Tor Vergata, Dipartimento Fis, I-00173 Rome, Italy
[11] Tibet Univ, Lhasa, Peoples R China
[12] SW Jiaotong Univ, Chengdu, Peoples R China
[13] Yunnan Univ, Kunming 650091, Peoples R China
[14] IHEP, Beijing, Peoples R China
[15] Univ Basilicata, I-85100 Potenza, Italy
[16] CNR, Ist Cosmogeofis, I-10133 Turin, Italy
[17] Ist Nazl Fis Nucl, I-10125 Turin, Italy