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HK: Fachverband Hadronen und Kerne

HK 66: Plenary VIII

HK 66.1: Eingeladener Hauptvortrag

Donnerstag, 19. März 2009, 11:00–11:30, Audi-Max

Precision experiments with cold and ultracold neutrons — •Klaus Kirch — Paul Scherrer Institut, Villigen PSI, Switzerland

The neutron is a composite particle, but a rather fundamental one. It is the experimentally easiest accessible, electrically neutral spin-1/2 particle. Neutrons take part in all known interactions: They are massive, have magnetic moments, interact strongly and decay weakly. Thermal and cold ("slow") neutrons can be guided to experiments because they are totally reflected from suitable material surfaces under grazing angles of incidence. Critical angles for total reflection depend on neutron velocity. Sufficiently slow neutrons are called ultracold when they are totally reflected under all angles of incidence.

Slow neutrons are particularly useful to test the fundamental interactions and symmetries of nature. They allow for long observation times and are relatively easy to polarize. Most neutron decay correlation studies make use of cold neutron beams which provide large decay statistics and today allow for almost complete neutron polarization. Other experiments, like the measurement of the neutron beta-decay lifetime or the search for an electric dipole moment of the neutron benefit from using stored, ultracold neutrons. Especially in these experiments, considerable progress can be expected due to increasing the available ultracold neutron intensity. To that end, the Paul Scherrer Institut in Switzerland, but also various other projects around the world, aim at providing larger intensities and densities of ultracold neutrons.