The AMS-02 RICH detector: Status and physics results

Abstract

The Alpha Magnetic Spectrometer (AMS-02) is a high-energy particle physics magnetic spectrometer installed on the International Space Station since May 2011, and operating continuously since then. Because of its large acceptance, long exposure time and particle identification capabilities, AMS-02 measures cosmic ray (CR) fluxes in the kinetic energy range between a fraction of GeV/n to multi-TeV/n with unprecedented precision. The AMS-02 Ring Imaging Cherenkov detector (RICH) provides a precise measurement of the particle velocity and charge. The detector has shown stable and nominal response during the past 7 years of continuous data taking without showing significant degradation. In combination with the Silicon Tracker momentum measurement, the RICH is able to measure the isotopic composition of the light elements (up to charge Z=5) in the kinetic energy range from a few GeV/n to about 10 GeV/n. This paper will focus on the separation of cosmic rays species with |Z|=1. For positive rigidities (Z=+1), the measurement of individual p and d fluxes and their ratio are important for the understanding of CR propagation in our galaxy, since deuterons are almost entirely the secondary products of interactions of cosmic rays with interstellar matter, while protons are mainly produced in astrophysical sources. The negative rigidity sample (Z=-1) is promising for indirect search of Dark Matter, looking at the p̄ and d̄ components. These species are rare secondary products of CR propagation and therefore an excess due to new physics could be more significantly seen on top of their faint expected flux. In particular, d̄ have never been observed so far in CR.