  The Alpha Magnetic Spectrometer (AMS-02) was installed on the International
Space Station (ISS) and it has been collecting data successfully since May
2011. The main goals of AMS-02 are the search for cosmic anti-matter, dark
matter and the precise measurement of the relative abundance of elements and
isotopes in galactic cosmic rays. In order to identify particle properties,
AMS-02 includes several specialized sub-detectors. Among them, the AMS-02 Ring
Imaging Cherenkov detector (RICH) is designed to provide a very precise
measurement of the velocity and electric charge of particles. We describe a
method to reject the dominant electron background in antiproton identification
with the use of the AMS-02 RICH detector as a veto for rigidities below 3 GV.
Ray tracing integration method is used to maximize the statistics of $\bar{p}$
with the lowest possible $e^{-}$ background, providing 4 times rejection power
gain for $e^{-}$ background with respect to only 3\% of $\bar{p}$ signal
efficiency loss. By using the collected cosmic-rays data, $e^{-}$ contamination
can be well suppressed within 3\% with $\beta \approx 1$, while keeping 76\%
efficiency for $\bar{p}$ below the threshold.
