[1] Univ Bologna, I-47921 Rimini, Italy
[2] INFN, Dip Sci Qualita Vita, I-47921 Rimini, Italy
[3] Univ Maryland, Dept Phys, Coll Pk, College Pk, MD 20742 USA
[4] Univ Roma Tor Vergata, Raimondo18, I-00173 Rome, Italy
[5] Univ Bern, Albert Einstein Ctr Fundamental Phys, CH-3012 Bern, Switzerland
[6] Austrian Acad Sci, Stefan Meyer Inst Subat Phys, Boltzmanngasse 3, A-1090 Vienna, Austria
[7] Lab Nazionali Frascati INFN, Via E. Fermi 40, I-00044 Frascati, Italy
[8] Pacif NW Natl Lab, 902 Battelle Blvd, Richland, WA 99352 USA
[9] Univ Oklahoma, Dept Phys & Astron, Norman, OK 73019 USA
[10] Univ Louisville, Louisville, KY 40292 USA
[11] Lawrence Berkeley Natl Lab, Div Phys, 1 Cyclotron Rd, Berkeley, CA 94720 USA
[12] CERN, European Org Nucl Res, CH-1211 Geneva 23, Switzerland
[13] Ohio State Univ, Dept Phys, 191 Woodruff Ave, Columbus, OH 43210 USA
[14] Inst High Energy Phys, COMPAS Grp, RU-142284 Protvino, Russia
[15] Max Planck Inst Phys & Astrophys, D-80805 Munich, Germany
[16] Univ Washington, Dept Phys, Seattle, WA 98195 USA
[17] Ludwig Maximilians Univ Munchen, Fak Physik, Schellingstr 4, D-80799 Munich, Germany
[18] Univ Chicago, Enrico Fermi Inst, Chicago, IL 60637 USA
[19] Univ Chicago, Dept Phys, Chicago, IL 60637 USA
[20] Columbia Univ, Dept Phys, 538 120th St, New York, NY 10027 USA
[21] Imperial Coll, Blackett Lab, High Energy Phys Grp, Prince Consort Rd, London SW7 2AZ, England
[22] Jefferson Lab, 12000 Jefferson Ave, Newport News, VA 23606 USA
[23] Univ Virginia, Dept Phys, POB 400714, Charlottesville, VA 22904 USA
[24] Fermilab Natl Accelerator Lab, POB 500, Batavia, IL 60510 USA
[25] Univ Chicago, Kavli Inst Cosmol Phys, Chicago, IL 60637 USA
[26] Univ Sussex, Dept Phys & Astron, Brighton BN1 9QH, E Sussex, England
[27] No Illinois Univ, Dept Phys, De Kalb, IL 60115 USA
[28] Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA
[29] Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA
[30] Univ London, Dept Phys, Royal Holloway, Egham TW20 0EX, Surrey, England
[31] INFN Sezione Napoli, Complesso Univ Monte St Angelo, Via Cintia, I-80126 Naples, Italy
[32] Inst Hautes Etud Sci, F-91440 Bures Sur Yvette, France
[33] UNSAM, ICAS, 25 Mayo Francia, RA-1650 Buenos Aires, DF, Argentina
[34] Northwestern Univ, Dept Phys & Astron, Evanston, IL 60208 USA
[35] Univ Colorado, Dept Phys, Boulder, CO 80309 USA
[36] Univ Amsterdam, NL-1012 WX Amsterdam, Netherlands
[37] Nikhef, POB 41882, NL-1009 DB Amsterdam, Netherlands
[38] ETH, Inst Particle Phys, CH-8093 Zurich, Switzerland
[39] Univ Liverpool, Dept Phys, Oliver Lodge Lab, Oxford St, Liverpool L69 3BX, Merseyside, England
[40] Univ Bonn, Physikal Inst, Nussallee 12, D-53115 Bonn, Germany
[41] Univ Helsinki, Helsinki Inst Phys, POB 64, FIN-00014 Helsinki, Finland
[42] Univ Helsinki, Dept Phys, POB 64, FIN-00014 Helsinki, Finland
[43] Budker Inst Nucl Phys, SB RAS, Novosibirsk 630090, Russia
[44] Novosibirsk State Univ, Novosibirsk 630090, Russia
[45] Kings Coll London, Dept Phys, London WC2R 2LS, England
[46] Univ Nacl Autonoma Mexico, Inst Fis, Dept Fis Teor, Mexico City 04510, DF, Mexico
[47] State Univ, Moscow Inst Phys & Technol, Moscow RU-141700, Russia
[48] Univ Illinois, Dept Astron, 1002 Green St, Urbana, IL 61801 USA
[49] Univ Illinois, Dept Phys, 1110 Green St, Urbana, IL 61801 USA
[50] Univ Hamburg, Notkestrasse 85, D-22607 Hamburg, Germany