An anomalous positron abundance in cosmic rays with energies 1.5-100 GeV
2009 (English)In: Nature, ISSN 0028-0836, Vol. 458, no 7238, 607-609 p.Article in journal (Refereed) Published
Antiparticles account for a small fraction of cosmic rays and are known to be produced in interactions between cosmic-ray nuclei and atoms in the interstellar medium(1), which is referred to as a 'secondary source'. Positrons might also originate in objects such as pulsars(2) and microquasars(3) or through dark matter annihilation(4), which would be 'primary sources'. Previous statistically limited measurements(5-7) of the ratio of positron and electron fluxes have been interpreted as evidence for a primary source for the positrons, as has an increase in the total electron+positron flux at energies between 300 and 600 GeV (ref. 8). Here we report a measurement of the positron fraction in the energy range 1.5-100 GeV. We find that the positron fraction increases sharply overmuch of that range, in a way that appears to be completely inconsistent with secondary sources. We therefore conclude that a primary source, be it an astrophysical object or dark matter annihilation, is necessary.
Place, publisher, year, edition, pages
2009. Vol. 458, no 7238, 607-609 p.
Astronomy, Astrophysics and Cosmology
IdentifiersURN: urn:nbn:se:su:diva-80703DOI: 10.1038/nature07942ISI: 000264796200035OAI: oai:DiVA.org:su-80703DiVA: diva2:557743