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Accepted · first revision · record

Title: Pulsars or dark matter as the source of excess cosmic positrons
Plain: There are more positrons, antimatter electrons, at high energies than collisions of ordinary cosmic rays with gas can make. Nearby pulsars or dark matter could supply them.
Precise: The positron fraction e+/(e+ + e-) rises above about 10 GeV (PAMELA, AMS-02), and the AMS-02 positron flux shows a high-energy drop-off near several hundred GeV. Identify the dominant extra source (nearby pulsars and their wind nebulae, dark-matter annihilation or decay, or secondary production in sources) by fitting the spectrum, its cutoff and the upper limits on dipole anisotropy.
Settled by: Detection or exclusion of the anisotropy or spectral structure predicted for nearby pulsars, combined with TeV electron spectra and diffusion constraints near pulsars.
Kind: well-posed
Answer type: identification
References: (empty)
Literature status: contested
Status note: TeV halos around Geminga and Monogem seen by HAWC show that pulsars release electron-positron pairs, but slow diffusion near them limits their contribution at Earth and the share remains debated.
Posed since: 2009