The solar flare of the 14th of July 2000 (L3+C detector results)

¹ III. Physikalisches Institut, RWTH, 52056 Aachen, Germany NIKHEF, and University of Amsterdam, 1009 DB Amsterdam, The Netherlands University of Michigan, Ann Arbor, MI 48109, USA Laboratoire d'Annecy-le-Vieux de Physique des Particules, LAPP, IN2P3-CNRS, BP 110, 74941 Annecy-le-Vieux Cedex, France Institute of Physics, University of Basel, 4056 Basel, Switzerland Louisiana State University, Baton Rouge, LA 70803, USA Institute of High Energy Physics, IHEP, 100039 Beijing, PR China ITP, Academia Sinica, 100039 Beijing, PR China University of Bologna and INFN-Sezione di Bologna, 40126 Bologna, Italy Tata Institute of Fundamental Research, Mumbai (Bombay) 400 005, India Northeastern University, Boston, MA 02115, USA Institute of Atomic Physics and University of Bucharest, 76900 Bucharest, Romania Central Research Institute for Physics of the Hungarian Academy of Sciences, 1525 Budapest 114, Hungary Massachusetts Institute of Technology, Cambridge, MA 02139, USA Panjab University, Chandigarh 160 014, India KLTE-ATOMKI, 4010 Debrecen, Hungary UCD School of Physics, University College Dublin, Belfield, Dublin 4, Ireland University of Florence and INFN, Sezione di Firenze, 50019 Sesto Fiorentino, Italy European Laboratory for Particle Physics, CERN, 1211 Geneva 23, Switzerland World Laboratory, FBLJA Project, 1211 Geneva 23, Switzerland University of Geneva, 1211 Geneva 4, Switzerland University of Hamburg, 22761 Hamburg, Germany Chinese University of Science and Technology, USTC, Hefei, Anhui 230 029, China University of Lausanne, 1015 Lausanne, Switzerland Institut de Physique Nucléaire de Lyon, IN2P3-CNRS,Université Claude Bernard, 69622 Villeurbanne, France Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, CIEMAT, 28040 Madrid, Spain Florida Institute of Technology, Melbourne, FL 32901, USA INFN – Sezione di Milano, 20133 Milan, Italy Institute of Theoretical and Experimental Physics, ITEP, Moscow, Russia INFN – Sezione di Napoli and University of Naples, 80125 Naples, Italy Department of Physics, University of Cyprus, Nicosia, Cyprus Radboud University and NIKHEF, 6525 ED Nijmegen, The Netherlands Osaka City University, Osaka 558-8585, Japan California Institute of Technology, Pasadena, CA 91125, USA INFN – Sezione di Perugia and Università Degli Studi di Perugia, 06100 Perugia, Italy Nuclear Physics Institute, St. Petersburg, Russia Carnegie Mellon University, Pittsburgh, PA 15213, USA INFN–Sezione di Napoli and University of Potenza, 85100 Potenza, Italy Princeton University, Princeton, NJ 08544, USA University of California, Riverside, CA 92521, USA INFN – Sezione di Roma and University of Rome, “La Sapienza”, 00185 Rome, Italy University and INFN, Salerno, 84100 Salerno, Italy University of California, San Diego, CA 92093, USA University of Santiago de Compostela, 15706 Santiago, Spain Bulgarian Academy of Sciences, Central Lab. of Mechatronics and Instrumentation, 1113 Sofia, Bulgaria The Center for High Energy Physics, Kyungpook National University, 702-701 Taegu, Republic of Korea National Central University, Chung-Li, Taiwan, China Department of Physics, National Tsing Hua University, Taiwan, PR China Purdue University, West Lafayette, IN 47907, USA Paul Scherrer Institut, PSI, 5232 Villigen, Switzerland DESY, 15738 Zeuthen, Germany Eidgenössische Technische Hochschule, ETH Zürich, 8093 Zürich, Switzerland *e-mail: Pierre.Le.Coultre@cern.ch Supported by the German Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie. Supported by the Hungarian OTKA fund under contract numbers T019181, F023259 and T037350. Also supported by the Hungarian OTKA fund under contract number T026178. Supported also by the Comisión Interministerial de Ciencia y Tecnología. Also supported by CONICET and Universidad Nacional de La Plata, CC 67, 1900 La Plata, Argentina. Supported by the National Natural Science Foundation of China. On leave from the Moscow Physical Engineering Institute (MePhl). On leave from JINR, 141980 Dubna, Russia. Deceased.

Received: 22 March 2006
Accepted: 8 May 2006

Abstract

Aims.Several experiments have reported observations on possible correlations between the flux of high energy muons and intense solar flares. If confirmed, these observations would have significant implications for acceleration processes in the heliosphere able to accelerate protons and other ions to energies of at least tens of GeV.

Methods.The solar flare of the 14 of July 2000 offered a unique opportunity for the L3+C experiment to search for a correlated enhancement in the flux of muons using the L3 precision muon spectrometer. Its capabilities for observing a directional excess in the flux of muons above 15 GeV (corresponding to primary proton energies above 40 GeV) are presented along with observations made on the 14th of July 2000.

Results.We report an excess which appeared at a time coincident with the peak increase of solar protons observed at lower energies. The probability that the excess is a background fluctuation is estimated to be 1%. No similar excess of the muon flux was observed up to 1.5 h after the solar flare time.