SPP 1491: Precision Experiments in Particle- and Astrophysics with Cold and Ultracold Neutrons

点击翻译按钮获取中文摘要

This Priority Programme wants to address some of the unsolved questions of modern science: the nature of the fundamental forces and underlying symmetries, as well as the nature of the gravitational force at very small distances. New facilities and technological developments now open the window for significant improvement in precision by one to two orders of magnitude over previous investigations. This allows to probe these questions in a complementary way to LHC-based experiments or even outline a unique way. The research programme will focus on four Priority Areas, which are directly related to specific physics/astrophysics issues: Priority Area A: CP-symmetry violation and particle physics in the early universe (addressed mainly by the search for the neutron electric dipole moment); Priority Area B: the structure and nature of weak interaction and possible extensions of the standard model (addressed mainly by precise studies of the neutron beta decay); Priority Area C: relation between gravitation and quantum theory (probed by investigations of low-energy bound states in the gravitational field); Priority Area D: charge quantisation and the electric neutrality of the neutron (probed by a precision test of the neutrons electric charge).The intended improvement in experimental precision has to go in parallel with the development of new or improved measurement techniques, which are often at the extreme border of feasibility. Novel powerful sources for ultracold neutrons are presently being prepared at various research centres. They will allow us to perform high-precision experiments on gravitation and the electric dipole moment of the neutron. On the other hand, neutron beta decay studies require a very brilliant source of decay products, i.e., a large active decay volume inside a cold neutron guide. These measurements should enable us to probe new physics almost independent of the mass scale (EDM) and to understand CP-symmetry violation in processes relevant to the matter-antimatter asymmetry of the universe. The structure of weak interaction can be tested with unprecedented precision, making possible to be sensitive to new intermediate bosons without direct observation. Thus, the origin of natures left-handedness observed today may be revealed. Precision studies of Newtons law at very small distances in turn allow to probe for extra dimensions at the µm level and can reveal the existence of new gauge bosons acting within. This again could hint to the space-time structure at very early times of the universe and is related to the curling up of extra space dimensions in the inflationary phase of the universe.