[1] Politecn Milan, Dept Phys, LNESS, Via Anzani 42, I-22100 Como, Italy
[2] INFN Milano, Via Celoria 16, I-20133 Milan, Italy
[3] Austrian Acad Sci, Stefan Meyer Inst Subat Phys, Boltzmanngasse 3, A-1090 Vienna, Austria
[4] Univ Brescia, Dept Mech & Ind Engn, Via Branze 38, I-25123 Brescia, Italy
[5] INFN Pavia, Via Bassi 6, I-27100 Pavia, Italy
[6] Univ Trento, Dept Phys, Via Sommar 14, I-38123 Povo, Trento, Italy
[7] TIFPA INFN Trento, Via Sommar 14, I-38123 Povo, Trento, Italy
[8] Univ Insubria, Dept Sci, Via Valleggio 11, I-22100 Como, Italy
[9] Univ Genoa, Dept Phys, Via Dodecaneso 33, I-16146 Genoa, Italy
[10] INFN Genova, Via Dodecaneso 33, I-16146 Genoa, Italy
[11] Univ Milan, Dept Phys, Via Celoria 16, I-20133 Milan, Italy
[12] Max Planck Inst Nucl Phys, Saupfercheckweg 1, D-69117 Heidelberg, Germany
[13] Univ Paris Saclay, Univ Paris Sud, Lab Aime Cotton, CNRS,ENS Paris Saclay, F-91405 Orsay, France
[14] Politecn Milan, Dept Aerosp Sci & Technol, Via La Masa 34, I-20156 Milan, Italy
[15] Heidelberg Univ, Kirchhoff Inst Phys, Neuenheimer Feld 227, D-69120 Heidelberg, Germany
[16] CERN, Phys Dept, CH-1211 Geneva 23, Switzerland
[17] Univ Oslo, Dept Phys, Sem Slandsvei 24, N-0371 Oslo, Norway
[18] Univ Lyon 1, CNRS IN2p3, Inst Nucl Phys, F-69622 Villeurbanne, France
[19] Russian Acad Sci, Inst Nucl Res, Moscow 117312, Russia
[20] Joint Inst Nucl Res, Dubna 141980, Russia
[21] INFN Padova, Via Marzolo 8, I-35131 Padua, Italy
[22] Heidelberg Univ, Dept Phys, Neuenheimer Feld 226, D-69120 Heidelberg, Germany
[23] Univ Bergen, Inst Phys & Technol, Allegaten 55, N-5007 Bergen, Norway
[24] Czech Tech Univ, Brehov 7, Prague 11519 1, Czech Republic
[25] Univ Bologna, Viale Berti Pichat 6-2, I-40126 Bologna, Italy
[26] Univ Pavia, Dept Phys, Via Bassi 6, I-27100 Pavia, Italy
[27] Res Council Norway, POB 564, NO-1327 Lysaker, Norway
[28] Univ Brescia, Dept Civil Engn, Via Branze 43, I-25123 Brescia, Italy