Search for New Physics with AMS-02 Transition Radiation Detector

Abstract

Today the universe consists of 4.6% of ordinary matter, 23.3% of dark matter and 72.1% of dark energy. The dark matter is generally assumed be stable, non-relativistic and only weakly interacting. But we do not know what the dark matter is made of and how it is distributed within our Galaxy. In general, the cosmic antiparticles are expected as secondary products of interactions of the primary cosmic-rays (CRs) with the interstellar medium during propagation. While the measurements of CR positrons have become more precise, the results still do not match with the pure secondary origins. AMS-02 is a large acceptance precision particle spectrometer approved for installation on the International Space Station (ISS). A key feature of AMS-02 is precise particle identification for measurements of primary cosmic ray anti-particle spectra with negligible background up to a momentum of 500 GeV/c to allow indirect searches for dark matter. To efficiently separate positrons/electrons from protons/anti-protons, AMS-02 will be equipped with a Transition Radiation Detector (TRD) with 5248 straw tube proportional counters filled with a Xe/CO₂ (80/20) mixture. The AMS-02 TRD was fully assembled and integrated into AMS-02 in 2007. In 2008 AMS-02 had recorded cosmic ray particles on ground to demonstrate full functionality of the device. For the AMS-02 TRD it will be shown that the detector response is as expected and the gas tightness will allow operation in space for 20 years with a gas supply of 25 kg.