Measurement of the Cosmic-Ray Antiproton-to-Proton Abundance Ratio between 4 and 50 GeV

A. S. Beach; J. J. Beatty; A. Bhattacharyya; C. Bower; S. Coutu; M. A. DuVernois; A. W. Labrador; S. McKee; S. A. Minnick; D. Müller; J. Musser; S. Nutter; M. Schubnell; S. Swordy; G. Tarlé; A. Tomasch

doi:10.1103/PhysRevLett.87.271101

Measurement of the Cosmic-Ray Antiproton-to-Proton Abundance Ratio between 4 and 50 GeV

A. S. Beach, J. J. Beatty, A. Bhattacharyya, C. Bower, S. Coutu, M. A. DuVernois, A. W. Labrador, S. McKee, S. A. Minnick, D. Müller, J. Musser, S. Nutter, M. Schubnell, S. Swordy, G. Tarlé, and A. Tomasch

Phys. Rev. Lett. 87, 271101 – Published 10 December 2001

Abstract

We present a new measurement of the antiproton-to-proton abundance ratio, $\bar{p} / p$ , in the cosmic radiation. The HEAT-pbar instrument, a balloon borne magnet spectrometer with precise rigidity and multiple energy loss measurement capability, was flown successfully in Spring 2000, at an average atmospheric depth of $7.2 g / {cm}^{2}$ . A total of 71 antiprotons were identified above the vertical geomagnetic cutoff rigidity of 4.2 GV. The highest measured proton energy was 81 GeV. We find that the $\bar{p} / p$ abundance ratio agrees with that expected from a purely secondary origin of antiprotons produced by primary protons with a standard soft energy spectrum.

Received 3 July 2001

DOI:https://doi.org/10.1103/PhysRevLett.87.271101

Authors & Affiliations

A. S. Beach¹, J. J. Beatty¹, A. Bhattacharyya², C. Bower², S. Coutu¹, M. A. DuVernois^1,*, A. W. Labrador^3,†, S. McKee⁴, S. A. Minnick¹, D. Müller³, J. Musser², S. Nutter^1,‡, M. Schubnell^4,§, S. Swordy³, G. Tarlé⁴, and A. Tomasch⁴

¹Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802
²Department of Physics, Indiana University, Bloomington, Indiana 47405
³Enrico Fermi Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637
⁴Department of Physics, University of Michigan, Ann Arbor, Michigan 48109

^*Now at School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455.
^†Now at California Institute of Technology, Pasadena, CA 91125.
^‡Now at Physics and Geology Department, Northern Kentucky University, Highland Heights, KY 41099.
^§Corresponding author.Email address: schubnel@umich.edu.