Ultracold Neutrons

TL;DR

Ultracold neutrons are crucial for precision measurements in fundamental physics, enabling tests of neutron properties and searches for new interactions, with PSI leading in high-intensity UCN source development.

Contribution

This paper provides an overview of ultracold neutron research, highlighting PSI's advancements and the nEDM collaboration's efforts in precision measurements and new physics searches.

Findings

PSI's UCN source is among the world's most advanced.

The nEDM collaboration has set leading limits on the neutron electric dipole moment.

Ultracold neutrons enable sensitive tests of fundamental symmetries.

Abstract

Ultracold neutrons (UCN) are free neutrons that can be stored in experimental setups for several minutes. Some of the most important properties of the neutron, such as its tiny permanent electric dipole moment and its beta decay lifetime, are best measured with UCN. Also searches for well motivated but yet unknown, hypothetical additional interactions are being pursued with UCN. Such measurements in the field of low-energy, precision physics may have far reaching implications from particle physics to cosmology. Most experiments are statistics limited and need high-intensity UCN sources. The UCN source at PSI is at the forefront of the field and home to the international nEDM collaboration and its world-leading search for the neutron electric dipole moment. This article aims at giving an overview of the fascinating research using ultracold neutrons emphasizing on activities at PSI including various physics side-analyses which were pioneered by the nEDM collaboration.