First Result from the Alpha Magnetic Spectrometer on the International Space Station: Precision Measurement of the Positron Fraction in Primary Cosmic Rays of 0.5-350 GeV


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Aguilar M., Alberti G., Alpat B., Alvino A., Ambrosi G., Andeen K., ...More

PHYSICAL REVIEW LETTERS, vol.110, no.14, 2013 (Journal Indexed in SCI) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 110 Issue: 14
  • Publication Date: 2013
  • Doi Number: 10.1103/physrevlett.110.141102
  • Title of Journal : PHYSICAL REVIEW LETTERS

Abstract

A precision measurement by the Alpha Magnetic Spectrometer on the International Space Station of the positron fraction in primary cosmic rays in the energy range from 0.5 to 350 GeV based on 6.8 x 10(6) positron and electron events is presented. The very accurate data show that the positron fraction is steadily increasing from 10 to similar to 250 GeV, but, from 20 to 250 GeV, the slope decreases by an order of magnitude. The positron fraction spectrum shows no fine structure, and the positron to electron ratio shows no observable anisotropy. Together, these features show the existence of new physical phenomena. DOI: 10.1103/PhysRevLett.110.141102