The Alpha Magnetic Spectrometer has released high-precision data for cosmic rays, and has verified an excess of positrons relative to expectations from cosmic ray interactions in the interstellar medium. An exciting and well-known possibility for the excess is production of electron-positron pairs by annihilating dark matter particles in the halo of the Galaxy. We have constructed a new scenario for propagation of cosmic rays, based on the 2000 SMILI results and various other astrophysics

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... ations and measurements, in which the positron excess is due to secondary production. The scenario is studied from a simple heuristic perspective, and also within the constraints of a diffusion-reacceleration model using GALPROP. The conclusions of each approach agree with one another, showing that the scenario agrees well with the observed positron flux, without any need for dark matter or other exotic production mechanisms.