DFG Priority Programme 1491 "Precision Experiments in Particle and Astrophysics with Cold and Ultracold Neutrons" 2010 - 2018
The aim of this priority programme is to address basic open questions in particle and astrophysics using a specific tool: the neutron, which allows the search for new physics becoming manifest itself as small deviations from expectations. Many neutron physics observables are sensitive to physics beyond the Standard Model emerging from superstrings (hypothetical gauge bosons in large extradimensions), supersymmetry (electric dipole moment prediction at the experimental limit) or other Grand Unified Theories (charge quantization). Basic properties of the quark-mixing Cabibbo-Kobayashi-Maskawa (CKM) matrix need to be tested. The breaking of symmetries such as parity P, time reversal T and combined charge conjugation and parity symmetry CP shall be investigated. CP violation is a requirement for dynamic generation of the baryon-antibaryon asymmetry of the universe. The research program will focus on five Priority Areas, which are directly related to specific physics/astrophysics issues and instrumentation.
- CP-symmetry violation and particle physics in the early universe. The focus is a next generation experiment to measure the neutron electric dipole moment with a sensitivity increased by at least one order of magnitude within the next six years.
- The structure and nature of weak interaction and possible extensions of the Standard Model. The focus will be on novel experiments on neutron β-decay related to symmetries and weak interaction.
- Tests of gravitation with quantum objects. The aim is to improve the experimental sensitivity of neutrons to gravity and to hypothetical short ranged forces.
- Charge quantization and the electric neutrality of the neutron. The aim is to make an improved measurement on the value of the neutron’s electric charge.
The intended gain in experimental precision requires the development of new or improved measurement techniques.
- New techniques: particle detection, magnetometry and neutron optics. Within the next three years, in the field of magnetometry, residual fields should be measured on a < 5 fT level meeting the requirements of neutron electric dipole measurements. New particle detectors are needed for the expected high count rate of cold and ultra-cold neutrons, efficient low-energy proton counting as well as low-energy electron spectroscopy. High-intensity experiments with instant count rates of up to 108/s require detectors with fast self triggering readout electronics, pulse-shape analysis, and data acquisition. The research programme requires developments of specialized neutron optics. One major issue is the control of systematic effects such as depolarization in neutron guides, the influence of magnetic field fluctuations on neutron polarization, and spin rotation.