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 medium1, which is referred to as a 'secondary source'. Positrons might also originate in objects such as pulsars2 and microquasars3 or through dark matter annihilation4, which would be 'primary sources'. Previous statistically limited measurements5, 6, 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 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.

An anomalous positron abundance in cosmic rays with energies 1.5-100 GeV / O., Adriani; Barbarino, Giancarlo; G., Bazilevskaya; DE ROSA, Gianfranca. - In: NATURE. - ISSN 0028-0836. - STAMPA. - 458:(2009), pp. 607-609. [10.1038/nature07942]

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

BARBARINO, GIANCARLO;DE ROSA, GIANFRANCA
2009

Abstract

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 medium1, which is referred to as a 'secondary source'. Positrons might also originate in objects such as pulsars2 and microquasars3 or through dark matter annihilation4, which would be 'primary sources'. Previous statistically limited measurements5, 6, 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 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.
2009
An anomalous positron abundance in cosmic rays with energies 1.5-100 GeV / O., Adriani; Barbarino, Giancarlo; G., Bazilevskaya; DE ROSA, Gianfranca. - In: NATURE. - ISSN 0028-0836. - STAMPA. - 458:(2009), pp. 607-609. [10.1038/nature07942]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11588/357433
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