An anomalous positron abundance in cosmic rays with energies 1.5-100 GeV

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, which is referred to as a 'secondary source'. Positrons might also originate in objects such as pulsars and microquasars or...

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Published in:Nature 2009-04, Vol.458 (7238), p.607-609
Main Authors: Picozza, P, Adriani, O, Barbarino, G. C, Bazilevskaya, G. A, Bellotti, R, Boezio, M, Bogomolov, E. A, Bonechi, L, Bongi, M, Bonvicini, V, Bottai, S, Bruno, A, Cafagna, F, Campana, D, Carlson, P, Casolino, M, Castellini, G, De Pascale, M. P, De Rosa, G, De Simone, N, Di Felice, V, Galper, A. M, Grishantseva, L, Hofverberg, P, Koldashov, S. V, Krutkov, S. Y, Kvashnin, A. N, Leonov, A, Malvezzi, V, Marcelli, L, Menn, W, Mikhailov, V. V, Mocchiutti, E, Orsi, S, Osteria, G, Papini, P, Pearce, M, Ricci, M, Ricciarini, S. B, Simon, M, Sparvoli, R, Spillantini, P, Stozhkov, Y. I, Vacchi, A, Vannuccini, E, Vasilyev, G, Voronov, S. A, Yurkin, Y. T, Zampa, G, Zampa, N, Zverev, V. G
Format: Article
Language:English
Subjects:
Astronomi och astrofysik
Astronomy
Astronomy and astrophysics
Astrophysics
Cosmic rays
DARK-MATTER
ELECTRONS
Emission
FRACTION
Fysik
Humanities and Social Sciences
letter
Magnetic fields
multidisciplinary
Natural history
NATURAL SCIENCES
NATURVETENSKAP
PARTICLE
Physics
Positrons
Protons
Science
Science (multidisciplinary)
Stars & galaxies
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Summary: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, which is referred to as a 'secondary source'. Positrons might also originate in objects such as pulsars and microquasars or through dark matter annihilation, which would be 'primary sources'. Previous statistically limited measurements 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 over much 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.
ISSN:0028-0836
1476-4687
1476-4687
1476-4679
DOI:10.1038/nature07942