Our group is conducting a research programm at the interface between particle physics and cosmology, addressing major puzzles towards a deeper understanding of the Universe, such as the origin of the matter-antimatter asymmetry or the nature of the Dark Energy. We are doing low energy precision experiments using mainly Ultra-cold neutrons (UCNs). Currently we are focussing on two main projects: the search for the neutron electric dipole moment (nEDM) at the Paul Scherrer Institute in Switzerland and the measurement of quantum states of neutrons in the gravity field (GRANIT) at the Institute Laue Langevin in Grenoble.
Bearing no electric charge, the neutron is hardly interacting with matter. However, in certain conditions, a neutron could be reflected at a surface, like light. This is a manifestation of the wave-particle duality. The ability for a neutron to bounce at a surface depends on its velocity. Fast neutrons are never reflected. Cold neutrons, being slower, can be reflected a small angle of incidence. Ultracold neutrons, with a velocity slower than 30 km/h, are reflected at any angle of incidence for almost all materials.
Making use of Ultracold neutrons
- Neutron storage
Ultracold neutrons can be stored in magnetic or material bottles. It is thus possible observe and manipulate neutrons for long periods, ranging up to several minutes (the mean decay lifetime of the neutron is 15 minutes). Experiments using stored Ultracold neutrons allow in general an increased sensitivity, in comparison with experiments using neutron beams. The measurement of the neutron electric dipole moment (the nEDM experiment) is profitting from this enhanced sensitivity.
- Studiing gravity
Due to their low velocity, gravity affects Ultracold neutrons a lot. A neutron with a velocity of 30 km/h can at most rise 3 m before falling down in the gravity field. Therefore Ultracold neutrons are a unique tool to study gravity in the microscopic world (the GRANIT experiment).