Fundamental physics with ultracold neutrons
Prof. Oliver Zimmer (Institut Laue-Langevin, Grenoble)

Ultracold neutrons (UCN) are an excellent probe to study fundamental symmetries and interactions. They can be held and manipulated in traps and thus enable high precision experiments complementary to high-energy physics and with impact on astrophysics and cosmology. Despite longstanding, the search for a non-vanishing electric dipole moment of the neutron is a hot topic pursued by many laboratories around the world. A non-zero result would provide strong evidence of CP violation beyond the CKM mechanism implemented into the standard model of particle physics and help understanding the creation of baryonic matter in the big bang. The neutron lifetime is another key observable investigated with ultracold neutrons. It determines the creation of the light chemical elements in the big bang and is still astonishingly poorly known. A plethora of further investigations comprises searches for dark matter seeking transitions of neutrons to hypothetic partner particles in a “mirror world”, searches for violation of the Lorentz invariance, searches for axion-like particles and searches for deviations from Newton’s gravity law at distances in the micrometre range. As an important prerequisite the construction of much improved UCN sources ranks on top of the agenda of many research groups around the world. This talk will give an overview of the field and also describe recent advances in UCN production at the ILL in Grenoble using superfluid helium as converter medium.