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Low energy antiprotons in the cosmic rays: A new upper limit |
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| Authors: | S P Ahlen S Barwick J J Beatty C R Bower G Gerbier R M Heinz D Lowder S McKee S Mufson J A Musser P B Price M H Salamon G Tarle A Tomasch B Zhou |
| Institution: | (1) Physics Department, Boston University, 02215 Boston, MA, USA;(2) Physics Department, Univ. of California, 94720 Berkeley, CA, USA;(3) Physics Department, Indiana University, 47405 Bloomington, IN, USA;(4) Physics Department, Univ. of Michigan, 48109 Ann Arbor, MI, USA;(5) Astronomy Department, Indiana University, 47405 Bloomington, IN, USA;(6) Present address: Physics Department, Univ. of Utah, 84112 Salt Lake City, UT, USA |
| Abstract: | Kinematics predicts the severe suppression of low-energy (<1 GeV) secondary antiprotons in the Galactic cosmic rays. Thus
the observation several years ago of a finite flux of low-energy antiprotons could not be explained with existing models of
cosmic ray propagation, which led to a plethora of theoretical speculation. We have recently flown a balloon-borne instrument
to measure the energy spectrum of cosmic-ray
, and have found no antiprotons in the energy interval 200–640 MeV (corrected to the top of the atmosphere). This yields an
upper limit to the
ratio of 5.5×10−5 (90% confidence level), well below and hence contradicting the earlier result. |
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