Cosmic-ray positron fraction measurement from 1 to 30 GeV with AMS-01

TL;DR

This work reports a measurement of the cosmic-ray positron fraction in the 1–30 GeV range using AMS-01 data, leveraging a converted bremsstrahlung photon topology to achieve strong proton suppression (~10^6). The analysis employs advanced event reconstruction, invariant-mass cuts, geomagnetic backtracking, and Monte Carlo-based background corrections to extract the positron fraction and to compute absolute e± fluxes, with results aligning with prior measurements and secondary-production models. Background control and a robust livetime/acceptance calculation underpin the reliability of both the fraction and flux results, although statistical uncertainties dominate due to the low signal yield. Overall, the study demonstrates the feasibility of high-purity positron measurements with a small, space-based detector and provides essential cross-checks for cosmic-ray propagation and potential exotic sources.

Abstract

A measurement of the cosmic ray positron fraction e+/(e+ + e-) in the energy range of 1-30 GeV is presented. The measurement is based on data taken by the AMS-01 experiment during its 10 day Space Shuttle flight in June 1998. A proton background suppression on the order of 10^6 is reached by identifying converted bremsstrahlung photons emitted from positrons.