[1] McGill Univ, Dept Phys, Montreal, PQ H3A 2T8, Canada
[2] Univ Utah, Dept Phys, Salt Lake City, UT 84112 USA
[3] Tanta Univ, Dept Phys, Tanta, Egypt
[4] Univ Massachusetts, Dept Phys, Amherst, MA 01003 USA
[5] Univ Leeds, Sch Phys & Astron, Leeds LS2 9JT, W Yorkshire, England
[6] Washington Univ, Dept Phys, St Louis, MO 63130 USA
[7] Iowa State Univ, Dept Phys & Astron, Ames, IA 50011 USA
[8] Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA
[9] Purdue Univ, Dept Phys, W Lafayette, IN 47907 USA
[10] Univ Coll Dublin, Sch Phys, Dublin, Ireland
[11] Univ Oxford, Dept Phys, Oxford OX1 3RH, England
[12] Grinnell Coll, Dept Phys, Grinnell, IA 50112 USA
[13] Penn State Univ, Dept Astron & Astrophys, University Pk, PA 16802 USA
[14] Adler Planetarium & Astron Museum, Dept Astron, Chicago, IL 60605 USA
[15] Natl Univ Ireland Univ Coll Galway, Dept Phys, Galway, Ireland
[16] Univ Arkansas, Dept Phys & Astron, Little Rock, AR 72204 USA
[17] Univ Delaware, Dept Phys & Astron, Sharp Lab, Newark, DE 19716 USA
[18] Argonne Natl Lab, Argonne, IL 60439 USA
[19] Depauw Univ, Dept Phys & Astron, Greencastle, IN 46135 USA
[20] Max Planck Inst Kernphys, D-69117 Heidelberg, Germany
[21] Galway Mayo Inst Technol, Dept Phys & Life Sci, Galway, Ireland
[22] Harvard Smithsonian Ctr Astrophys, Fred Lawrence Whipple Observ, Amado, AZ 85645 USA
[23] NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA
[24] Univ Chicago, Enrico Fermi Inst, Chicago, IL 60637 USA