Method of Separating Cosmic-Ray Positrons from Electrons in the DAMPE Experiment

A method of identifying positron/electron species from the cosmic rays was studied in the DAMPE experiment. As there is no onboard magnet on the satellite, the different features imposed by the geomagnetic field on these two species were exploited for the particle identification. Application of this method to the simulation of on-orbit electrons/positrons/protons and the real flight data proves that separately measuring the CR positrons/electrons with DAMPE is feasible, though limited by the field of view for the present observation data. Further analysis on the positron flux with this method can be expected in the future.

Cosmic-ray positrons strongly constrain leptophilic dark matter

Cosmic-ray positrons have long been considered a powerful probe of dark matter annihilation. In particular, myriad studies of the unexpected rise in the positron fraction have debated its dark matter or pulsar origins. In this paper, we instead examine the potential for extremely precise positron measurements by AMS-02 to probe hard leptophilic dark matter candidates that do not have spectral features similar to the bulk of the observed positron excess. Utilizing a detailed cosmic-ray propagation model that includes a primary positron flux generated by Galactic pulsars in addition to a secondary component constrained by He and proton measurements, we produce a robust fit to the local positron flux and spectrum. We find no evidence for a spectral bump correlated with leptophilic dark matter, and set strong constraints on the dark matter annihilation cross-section that fall below the thermal annihilation cross-section for dark matter masses below 60 GeV and 380 GeV for annihilation into τ+τ- and e+e-, respectively, in our default model.

Fresh insights on properties of particle fluxes in cosmic rays measured with the Alpha Magnetic Spectrometer on the international space station

The Alpha Magnetic Spectrometer is a particle physics detector focusing on the search for dark matter, the existence of antimatter, the origin and composition of cosmic rays from primordial sources in the universe and the exploration of new physics in space. Important features of the elementary particle (proton, antiproton, positron and election) fluxes in cosmic rays are presented: (1) The proton spectrum has a smooth hardening from 200 GeV; (2) antiproton and positron spectra show excess from traditional physics background; (3) in particular, the positron flux shows a source term with a cutoff energy of 810 GeV, which raises the question of its source; (4) the origin of the energetic electrons is different from that of positrons and (5) the identical momentum dependence of primary and secondary cosmic ray nuclei fluxes are also reviewed.