[1] Gran Sasso Sci Inst, Laquila, Italy
[2] Univ Edinburgh, Sch Phys & Astron, SUPA, Edinburgh, Midlothian, Scotland
[3] Univ Genoa, Dipartimento Fis, Genoa, Italy
[4] Osservatorio Astron Collurania, INAF, Teramo, Italy
[5] Ist Nazl Fis Nucl, Sez Napoli, I-80125 Naples, Italy
[6] Univ Padua, Dipartimento Fis & Astron, Padua, Italy
[7] Ist Nazl Fis Nucl, Sez Padova, Padua, Italy
[8] Univ Notre Dame, Joint Inst Nucl Astrophys, Inst Struct & Nucl Astrophys, Notre Dame, IN 46556 USA
[9] Univ Naples Federico II, Dipartimento Fis, Naples, Italy
[10] Univ Naples 2, Dipartimento Matemat & Fis, Caserta, Italy