Antiproton identification below threshold with AMS-02 RICH detector

TL;DR

This paper presents a novel method using the AMS-02 RICH detector to effectively identify antiprotons below threshold by rejecting electron background, achieving high purity and efficiency in cosmic-ray measurements.

Contribution

The paper introduces a ray tracing integration method that enhances antiproton identification by significantly reducing electron contamination below 3 GV rigidity.

Findings

Achieved 4 times rejection power for electron background.

Suppressed electron contamination within 3% at β ≈ 1.

Maintained 76% efficiency for antiprotons below threshold.

Abstract

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.