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| Dissertation / PhD Thesis | FZJ-2017-04605 |
2017
RWTH Aachen University
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Please use a persistent id in citations: doi:10.18154/RWTH-2017-03791
Abstract: The interest in electric dipole moment (EDM) experiments is highly motivated by the problem of matter-antimatter asymmetry in our universe. New sources of CP-violation are needed to explain that phenomenon properly. An EDM of an elementary particle is a perfect candidate to search for these sources because its existence requires CP-violation beyond the Standard Model to be detected. New experiments for the EDM of charged hadrons are proposed. These experiments require a new type of storage ring to be built. Since an EDM could be as small as 10-29 e·cm, a fantastic precision should be achieved. The main cause that limits a potential sensitivity of future experiments are systematic errors. This thesis investigates possible ways to minimize various systematic errors for two versions of a new storage ring and for the precursor experiment, which will be performed by the JEDI (Jülich Electric Dipole moments Investigations) collaboration at the existing Cooler Synchrotron COSY. To study the impact of the systematic errors a large number of spin-orbit tracking simulations were performed in the newly developed program MODE. Two approaches for using a new storage ring were studied: the frozen and the quasi-frozen spin method. In addition, the precursor experiment at COSY was studied. The results of a test run conducted in 2014 made possible to benchmark and adjust the accelerator model and improve the simulation environment. One of the main quantities that defines the sensitivity is the spin decoherence, which takes place at any storage ring. The finite size of the bunch in all three directions, radial, vertical and longitudinal causes the particles’ spins to decohere. Using an RF cavity and a combination of sextupoles allows one to maximize the time during which the spins stay parallel to each other in the horizontal plane. The main source of systematic error is the misalignment of the elements inside the ring. For a dedicated storage ring, it was proposed to launch two beams in opposite directions (clockwise and counter-clockwise) to average out its impact. For the precursor experiment, the frequency mismatch between an RF Wien filter device that will be used and the frequency of the spin rotation is harmful. All error sources were thoroughly studied and the sensitivity limits were calculated. The EDM limit, which can currently be reached on the future experiments, is of the order of 10$^{-25}$ ─ 10$^{-26}$ e·cm. With the present situation at COSY, the accuracy of the precursor experiment is expected to be of the order of 10$^{-19}$ e·cm.
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