[1] Politecn Milan, I-20133 Milan, Italy
[2] Ist Nazl Fis Nucl Milano, I-20133 Milan, Italy
[3] Univ Bern, Albert Einstein Ctr Fundamental Phys, Lab High Energy Phys, CH-3012 Bern, Switzerland
[4] Univ Brescia, Dept Mech & Ind Engn, I-25123 Brescia, Italy
[5] Ist Nazl Fis Nucl Pavia, I-27100 Pavia, Italy
[6] Heidelberg Univ, Kirchhoff Inst Phys, D-69120 Heidelberg, Germany
[7] CERN, Dept Phys, CH-1211 Geneva 23, Switzerland
[8] Univ Trent, Dept Phys, Trento, Italy
[9] TIFPA, Ist Nazl Fis Nucl Trento, Trento, Italy
[10] Univ Paris Sud, Ctr Natl Rech Sci, ENS Cachan, Lab Aim Cotton, F-91405 Orsay, France
[11] Univ Insubria, Dept Sci, I-22100 Como, Italy
[12] Univ Genoa, Dept Phys, I-16146 Genoa, Italy
[13] Ist Nazl Fis Nucl Genova, I-16146 Genoa, Italy
[14] Univ Milan, Dept Phys, I-20133 Milan, Italy
[15] Max Planck Inst Nucl Phys, D-69117 Heidelberg, Germany
[16] Czech Tech Univ, Prague 11519, Czech Republic
[17] Univ Bergen, Inst Phys & Technol, N-5007 Bergen, Norway
[18] Russian Acad Sci, Inst Nucl Res, Moscow 117312, Russia
[19] Univ Oslo, Dept Phys, N-0371 Oslo, Norway
[20] Austrian Acad Sci, Stefan Meyer Inst Subat Phys, Boltzmanngasse 3, A-1090 Vienna, Austria
[21] Joint Nucl Res Inst, Dubna 141980, Russia
[22] Ist Nazl Fis Nucl Padova, I-35131 Padua, Italy
[23] Univ Lyon 1, Ctr Natl Rech Sci, Inst Nucl Phys, F-69622 Villeurbanne, France
[24] Univ Bologna, I-40126 Bologna, Italy
[25] Univ Pavia, Dept Phys, I-27100 Pavia, Italy
[26] Univ Naples Federico II, Dept Phys, I-80126 Naples, Italy
[27] Res Council Norway, Lysaker, Norway
[28] Univ Brescia, Dept Civil Engn, I-25123 Brescia, Italy