Pergamon www.elsevier.cotnAocate/asr zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Adv. Space Res. Vol. 27, No. 4, pp. 669-614,2001 0 2001COSPAR. Published by Elsevier Science Ltd. All rights reserved Printed in Great Britain 0273-1177/01$20.00 + 0.00 PII: SO273-1177(01)00108-9 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQP MEASUREMENTS OF COSMIC-RAY ELECTRONS AND POSITRONS BY THE WIZARD/CAPRICE COLLABORATION M. Boeziol, G. Barbiellini’ , V. Bonvicinl ‘l, P. Schiavon’, A. Vacchi’, N. Zampa’, D. Bergstrijm2, P. Carlson2, T. Francke2, S. Grinstein 2, N. Weber2, M. Suffert3, M. Hof4, J. Kremer4, W. Menn4, M. Simon4, S. A. Stephens5 M. Ambriola6, R. Bellotti’, F. S. Cafagna’, F. Ciacio’, M. Circella’, C. De Marzo’, N. Finetti7, P. Papini7, S. Piccardi7, P. Spillantini7, S. Bartalucci’, M. Ricci8, C. Grimanig M. Casolinol’, M.P. De Pascale lo, A. Morselli”, P. Picozza lo, R. Sparvoli”, J.W. Mitchell”, J.F. Ormes.l’, R.E. Streitmatter 11, U. Bravar12, and S.J. Stochaj12 1 Dipartimento di Fisica dell’llniversitci and Setione INFN di Trieste, Via A. Valerio 2, I- 34147 Trieste, Italy 2Royal Institute of Technology (KTH), S- 104 05 Stockholm, Sw eden 3Centre des Recherches Nucle’aires, BP20, F-67037 Strasbourg-Cedez, France 4 Universitiit Siegen, 57068 Siegen, Germany 5Tata Institute of Fundamental Research, Bombay 400 005, India 6Dipartimento di Fisica dell’UniversiM and Sezione INFN di Bari, Via Amendola 173, I- 70126 Bari, Italy 7Dipartimento di Fisica dell’Universit& and Sezione INFN di Firenze, Largo Enrico Fermi 2, I- 50125 Firenze, Italy 8Laboratori Nazionali INFN, Via Enrico Fermi 40, CP 13, I-00044 Frascati, Italy ‘Istituto di Fisica dell’universitci di Urbino, Urbino, Italy “Dipartimento di Fisica dell’Universitci and Se&one INFN Hi Roma, Tor Vergata, Via della Ricerca Scientifica 1, I- 00133 Roma, Italy I1 Code 661, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA l2 Box 3-PAL, New Mexico State University, Las Cruces, NM 88003, USA ABSTRACT Two recent balloon-borne experiments have been performed by the Wizard/CAPRICE collaboration in order to study the electron and positron components in the cosmic radiation. On 1994 August 8-9 the CAPRICE94 experiment flew from norther Canada and on 1998 May 28-29 the CAPRICE98 experiment flew from New Mexico, USA at altitude8 corresponding to 3.9 and 5.5 g/cm2 of average residual atmosphere respectively. The apparatus were equipped with a Ring Imaging Cherenkov (RICH) detector, a time-of-flight system, a superconducting magnet spectrometer with a tracking system and a 7-radiation-length silicon-tungsten imaging calorimeter. The RICH used in 1994 had a solid NaF radiator while in 1998 the RICH had a CbFlO gaseous radiator. We report on the electron and positron spectra and positron fraction at the top of the atmosphere from few hundred MeV to 40 GeV measured by these two experiments. 0 200 1 COSPAR. Published by Elsevier Science Ltd. All rights reserved. INTRODUCTION Precise measurements of the electron component of the cosmic radiation provide important information about the propagation of the cosmic rays in the Galaxy which is not accessible from the study of cosmic- ray nuclear components. In fact, because of their low mass, electrons undergo severe energy loss through synchrotron radiation in the magnetic field and inverse Compton scattering with the ambient photons. Along with the measurements of electrons, the study of the cosmic-ray positrons, which are believed to be 669