The spectral shape of cosmic ray positrons and antiprotons has been accurately measured in the broad kinetic energy range 1–350 GeV. In the higher part of this range ($E\gtrsim 30\mathrm{GeV}$), the $e^{+}$ and $\overline{p}$ are both well described by power laws with spectral indices ${\gamma }_{e^{+}}\simeq 2.77\pm 0.02$ and ${\gamma }_{\overline{p}}\simeq 2.78\pm 0.04$ that are approximately equal to each other and to the spectral index of protons. In the same energy range, the positron-antiproton flux ratio has the approximately constant value $2.04\pm 0.04$, that is consistent with being equal to the ratio $e^{+}/\overline{p}$ calculated for the conventional mechanism of production, where the antiparticles are created as secondaries in the inelastic interactions of primary cosmic rays with interstellar gas. The positron-antiproton ratio at lower energy is significantly higher (reaching a value $e^{+}/\overline{p}\approx 100$ for $E\approx 1\mathrm{GeV}$), but, in the entire energy range 1–350 GeV, the flux ratio is consistent with being equal to the ratio of the production rates in the conventional mechanism, as the production of low-energy antiprotons is kinematically suppressed in collisions with a target at rest. These results strongly suggest that cosmic ray positrons and antiprotons have a common origin as secondaries in hadronic interactions. This conclusion has broad implications for the astrophysics of cosmic rays in the Galaxy.

• Received 5 August 2016

DOI:https://doi.org/10.1103/PhysRevD.95.063009