[1] Univ Roma La Sapienza, Dipartimento Fis, I-00185 Rome, Italy
[2] Univ Roma La Sapienza, ICRA, I-00185 Rome, Italy
[3] ICRANet, I-65122 Pescara, Italy
[4] Univ Nice Sophia Antipolis, ICRANet, F-06103 Nice 2, France
[5] Al Farabi Kazakh Natl Univ, Phys Tech Fac, Alma Ata 050040, Kazakhstan