EPJ Web Conf.
Volume 208, 2019ISVHECRI 2018 - XX International Symposium on Very High Energy Cosmic Ray Interactions
|Number of page(s)||5|
|Section||Astroparticle Theory (+HECR)|
|Published online||10 May 2019|
Cosmic ray e± at high energy
Department of Particle Physics & Astrophysics, Weizmann Institute of Science, Rehovot, Israel
2 CERN Theory Department
3 Bethe Center for Theoretical Physics and Physikalisches Institut der Universität Bonn, Nußallee 12, 53115 Bonn, Germany
Published online: 10 May 2019
There is a commonly expressed opinion in the literature, that cosmic-ray (CR) e+ come from a primary source, which could be dark matter or pulsars. In these proceedings we review some evidence to the contrary: namely, that e+ come from secondary production due to CR nuclei scattering on interstellar matter. We show that recent measurements of the total e± flux at E ≲ 3 TeV are in good agreement with the predicted flux of secondary e±, that would be obtained if radiative energy losses during CR propagation do not play an important role. If the agreement between data and secondary prediction is not accidental, then the requirement of negligible radiative energy losses implies a very short propagation time for high energy CRs: tesc ≲. 105 yr at rigidities R ≳ 3 TV. Such short propagation history may imply that a recent, near-by source dominates the CRs at these energies. We review independent evidence for a transition in CR propagation, based on the spectral hardening of primary and secondary nuclei around R ~ 100 GV. The transition rigidity of the nuclei matches the rigidity at which the e+ flux saturates its secondary upper bound.
© The Authors, published by EDP Sciences, 2019
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