[1] LOUISIANA STATE UNIV, DEPT PHYS & ASTRON, BATON ROUGE, LA 70803 USA
[2] IST SUPER SANITA, RADIAT LAB, I-00161 ROME, ITALY
[3] UNIV CLERMONT FERRAND, PHYS CORPUSCULAIRE LAB, F-63170 AUBIERE, FRANCE
[4] UNIV BASEL, DEPT PHYS, CH-4051 BASEL, SWITZERLAND
[5] IST NAZL FIS NUCL, SEZ SANITA, ROME, ITALY
[6] IST NAZL FIS NUCL, NATL FRASCATI LABS, FRASCATI, ITALY