[1] Univ Trieste, INFN Sect, I-34127 Trieste, Italy
[2] Univ Trieste, Dept Phys, I-34127 Trieste, Italy
[3] Royal Inst Technol, KTH, Stockholm, Sweden
[4] Univ Siegen, D-5900 Siegen, Germany
[5] Tata Inst Fundamental Res, Bombay 400005, Maharashtra, India
[6] Univ Bari, INFN Sect, I-70121 Bari, Italy
[7] Univ Bari, Dept Phys, Bari, Italy
[8] Univ Florence, Dept Phys, Florence, Italy
[9] Univ Florence, INFN Sect, Florence, Italy
[10] Ist Nazl Fis Nucl, Nazl Frascati Lab, I-00044 Frascati, Italy
[11] Univ Roma Tor Vergata, INFN Sect, Rome, Italy
[12] Univ Roma Tor Vergata, Dept Phys, Rome, Italy
[13] NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA
[14] New Mexico State Univ, Las Cruces, NM 88003 USA
[15] Univ Roma Tor Vergata, Dept Elect Engn, Rome, Italy
[16] AF Ioffe Phys Tech Inst, St Petersburg, Russia
[17] PN Lebedev Phys Inst, Moscow, Russia
[18] Moscow Engn & Phys Inst, Moscow, Russia
[19] CNR, Ist Ric Onde Elettromagnet, I-50127 Florence, Italy