Search for the electric dipole moment of the neutron

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Electric dipole moments (EDM) measurements are among the most important searches for physics beyond the standard model of particle physics (SM). An EDM is a property of a fundamental system, which is forbidden in the SM, but should be present in most possible models describing physics beyond the SM. With an energy resolution of 10-22 eV, the experiments searching for this parameter are among the most precise measurements ever performed. Due to its comparably simple composition, the EDM of the neutron is a very prominent system and has already ruled out or restricted many new-physics models. With our new experiment we aim to achieve a significantly better sensitivity compared to the state of the art.Within the Schwerpunktprogramm on slow neutron physics, we have prepared an apparatus to measure the EDM of the neutron with enhanced sensitivity. The apparatus is the first of its kind, providing a unique possibility to control the most critical systematic effects. Although the apparatus is placed at the FRM-II, it has been built portable and modular, also in view of the long delays of the UCN source at the FRM-II.In spring 2016, the Institut Laue-Langevin (ILL) made an international call for a flagship-experiment at the enhanced version of the currently strongest existing UCN source. Our apparatus won this competition, which enables us to perform a highly competitive experiment, by combining the best control of systematics with the strongest existing UCN source. We aim for a more-than-one order of magnitude improvement of the sensitivity to the low 10-27 ecm regime within this proposal.Our project plans to use the investments from the SPP program in the most efficient way: we plan to (i) adapt our apparatus for the new UCN source at ILL. We plan to make only minor adaptations to the existing hardware; (ii) move part of the hardware of the EDM apparatus from FRM-II to ILL, set it up at the new beam position and operate it in the new environment; (iii) characterize the performance of the apparatus with UCN and perform EDM measurements. (iv) In parallel we continue to work at TUM with the outer magnetic shield for R&D, preparation, test and education purpose. Maintaining the capability for work in such an environment at TUM is important and we have a well-defined focus on specific items listed in the proposal, enhanced by our long-term partner PTB, who submit a proposal also in this week, which is closely linked to our proposal.We are aware that we will not finish the EDM runs within this project, but we can realistically perform a competitive measurement within the scope of this proposal. The long-term strategy, which is based on this proposal, also involves major possible updates of the hardware, provided by Rutherford Lab, enabling various options for a long-term strategy involving ILL and FRM-II simultaneously.