Dr. Martin Simon
Subject area: Physik
What it is: To date no violation of the symmetry of CPT (combination of Charge, Parity and Time) has been observed. The Theorem of CPT predicts that particles and antiparticles have identical (or exactly opposite) properties and therefore, in case of atoms, the same characteristic spectrum. Nevertheless the matter and antimatter asymmetry in the universe is quantitatively unexplained. The ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons) collaboration at the Antiproton Decelerator CERN aims to investigate this issue by measuring the ground state hyperfine structure of antihydrogen, the simplest antiatom. A Rabi-like spectrometer line has been build consisting of a microwave cavity, a super conducting sextupole magnet and a detector for counting antihydrogen atoms composed of a position sensitive central detector and a hodoscope. This contribution will focus on the two layer hodoscope made up of plastic scintillators which are read out by silicon photo multipliers (SiPM) with pre-amplifier electronics. The challenging task of the detector is to discriminate between background events and antiproton annihilations originating from antihydrogen atoms which are produced only in small amounts.