Speaker
Description
Free neutrons moving at pedestrian speed, also called Ultra-Cold Neutrons (UCNs), have low enough energy to become confined and manipulated in traps. Being electrically neutral but being affected by all known fundamental forces they are an excellent probe to study fundamental symmetries and interactions. Storage lifetimes of several hundred seconds enable high-precision experiments with impact on astrophysics and cosmology, complementary to high-energy physics. Although started more than 50 years ago, the search for a non-vanishing electric dipole moment of the neutron is currently a hot topic pursued by many research groups around the world. Increasingly accurate experiments test new scenarios of time reversal invariance violation which is required for an explanation of the matter-antimatter asymmetry in our Universe. Also the neutron lifetime is a key observable investigated with UCNs. It determines the primordial abundances of the light chemical elements after the big bang and is still astonishingly poorly known. A third example of present studies covered in this talk is a search for deviations from Newton’s gravity law at distances in the micrometre range, using spectroscopy of quantum states of the neutron confined by a horizontal mirror and gravity. Accuracies of most experiments using UCNs are still statistics limited and can thus be much improved with advances in UCN production, which is the goal of an ongoing development of superfluid-helium based UCN sources at the ILL in Grenoble.
