[en] The theoretical description of nature, within the standard model framework of particle physics, gives rise to a manifold of different symmetries. The most fundamental one is the combined symmetry of charge conjugation, parity transformation, and time reversal (CPT symmetry). Currently all experimental evidence opposes the idea of a broken CPT symmetry. The ASACUSA collaboration, at the ^Antiproton Decelerator^, at the European Organisation for Nuclear Research (CERN), tries to measure the ground state hyperfine splitting of antihydrogen. By comparing this splitting with the similar signal in ordinary hydrogen, the CPT symmetry can be directly tested. During the course of this thesis, a detector system for detecting annihilations from antihydrogen at the end of the experimental setup was developed. In this work the construction of the detector will be described in detail, including control and data acquisition of the setup. A special focus will be on the electronic components, the inner working of the data acquisition, and the structure of the measured data. The recorded data was analysed using Bayesian methods. Both, the identification of annihilation events and their consequent distinction from background signals, and the statistical analysis of the data are covered in detail. Finally, based on the statistical analysis, the data significance is presented. (author)

[en] Full text: The b-decay of neutrons gives access to the structure and nature of the weak interaction. Main emphasis lies on tests of the validity of the Standard Model (unitarity of the Cabibbo-Kobayashi-Maskawa matrix) and searches for possible extensions (e.g., right-handed currents, SUSY). Therefore, we study angular correlations involving the neutron spin and the momenta of the b-decay products (electrons and protons) with the new facility PERC. Different methods for electron energy spectroscopy, simultaneous electron and proton momentum spectroscopy, and proton spectroscopy are under development. So far, the efficiency of a scintillation detector with photomultiplier readout is investigated. The advantage of scintillation detectors is a short readout time with time resolution of 1 ns, which is needed for high count rate spectroscopy with PERC. The principles of PERC, different detection systems as well as first results of our efficiency studies, with calibration sources, are presented in this poster. (author)

[en] The ASACUSA collaboration aims to measure the ground state hyperfine splitting (GS-HFS) of antihydrogen, the antimatter counterpart to atomic hydrogen. Comparisons of the corresponding transitions in those two systems will provide sensitive tests of the CPT symmetry, the combination of the three discrete symmetries charge conjugation, parity, and time reversal. For offline tests of the GS-HFS spectroscopy apparatus we constructed a source of cold polarised atomic hydrogen. In these proceedings we report the successful observation of the hyperfine structure transitions of atomic hydrogen with our apparatus in the earth’s magnetic field

[en] One of the ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons) collaboration’s goals is the measurement of the ground state hyperfine transition frequency in antihydrogen, the antimatter counterpart of one of the best known systems in physics. This high precision experiment yields a sensitive test of the fundamental symmetry of CPT. Numerical simulations of hyperfine transitions of antihydrogen atoms have been performed providing information on the required antihydrogen events and the achievable precision

[en] The ASACUSA antihydrogen setup at the CERN Antiproton Decelerator (AD) consists of an antihydrogen source (cusp magnet coupled to a positron source and an antiproton catching magnet) followed by a spectrometer beamline. After production in the cusp, the antihydrogen atoms decay while they escape the trap leading to changes in their effective magnetic moment which in turn affect their trajectories in the beamline. Those sequential decays in the presence of a varying magnetic field strength from their production point in the cusp to their detection at the end of the spectrometer line can in principle greatly affect the prospects for a precision measurement of the antihydrogen hyperfine splitting given the so-far relatively low number of available anti-atoms. The impact of the antihydrogen decay in this context has for the first time been simulated. The implementation of atomic radiative decay has been done in Geant4 to extend the particle tracking capabilities originally embedded in Geant4 to excited atoms, and to allow studies of the effect of dynamic atomic properties on trajectories. This new tool thus allows the study of particle–matter interaction via the Geant4 toolkit while properly taking into account the atomic nature of the object under study. The implementation as well as impacts on the experimental sensitivity for antihydrogen spectroscopy are discussed in this paper. (paper)

[en] A measurement of the hyperfine structure of antihydrogen promises one of the best tests of CPT symmetry. We describe an experiment planned at the Antiproton Decelerator of CERN to measure this quantity in a beam of slow antihydrogen atoms.

[en] The PERC collaboration will perform high-precision measurements of angular correlations in neutron beta decay at the beam facility MEPHISTO of the Forschungs-Neutronenquelle Heinz Maier-Leibnitz in Munich, Germany. The new beam station PERC, a clean, bright, and versatile source of neutron decay products, is designed to improve the sensitivity of neutron decay studies by one order of magnitude. The charged decay products are collected by a strong longitudinal magnetic field directly from inside a neutron guide. This combination provides the highest phase space density of decay products. A magnetic mirror serves to perform precise cuts in phase space, reducing related systematic errors. The new instrument PERC is under development by an international collaboration. The physics motivation, sensitivity, and applications of PERC as well as the status of the design and preliminary results on uncertainties in proton spectroscopy are presented in this paper.

[en] Full text: Precision measurements of observables in low-energy neutron beta decay address a number of questions which are at the forefront of particle physics, being complementary to direct searches in high-energy physics. Main emphasis is put on the unprecedentedly precise determination of angular correlation coefficients of the neutron decay from which the search for new physics beyond the Standard Model may be enabled. The new PERC (Proton Electron Radiation Channel) instrument, being part of the priority program 'Precision experiments in particle and astrophysics with cold and ultra-cold neutrons', will be installed on a high-flux cold neutron guide at the FRM II neutron source in Garching by an international collaboration. As its principal feature the charged decay products are collected by a strong longitudinal magnetic field inside a neutron guide. This combination provides the highest phase space density of decay products. Count rates of neutron decay products will be increased by a factor 100 compared to the best experiments so far. An adjustable magnetic mirror serves to limit the phase space precisely which allows for a reduction of related systematic errors. The accuracy of electron spectroscopy e.g. has been estimated to be on the 10^-4 level, about an order of magnitude better than the present day value. Here, we present the physics background to the project and the current status of design and realization of the instrument. (author)

[en] We have been developing ground-state antihydrogen atomic beams to test CPT symmetry via in-flight hyperfine spectroscopy. A new antihydrogen beam detector has been developed. The overview of the experiment, the detail of the detector and latest results will be presented. (paper)

[en] We report the successful commissioning and testing of a dedicated field-ioniser chamber for measuring principal quantum number distributions in antihydrogen as part of the ASACUSA hyperfine spectroscopy apparatus. The new chamber is combined with a beam normalisation detector that consists of plastic scintillators and a retractable passivated implanted planar silicon (PIPS) detector.