27. November 2007

Excursion in the wondrous Mirror World

Matter and Material Particle Physics

In physics, mirror matter, is a hypothetical counterpart to ordinary matter and not be mixed up with antimatter. It could explain symmetry violations observed in several processes of ordinary elementary particles. Symmetry could be restored by so called mirror particles with exactly the same mass as ordinary elementary particles. The mirror matter could form planets, stars, and galaxies and yet shares only gravitational interactions with the matter of our universe. By coupling to that idea the overwhelming evidence from astrophysical observations indicating that a considerable amount of our universe is made of matter we simply cannot see, so called dark matter, there arises a strong motivation to put the idea to an experimental test. Since only experiment can decide about the nature of the missing mass, physicists are actively searching for experimental evidence of mirror matter.

The laws of physics do state that, under certain conditions, an exchange of particles can occur between our real world and the mirror world – nearly as with Alice. The ultracold neutrons group of the Paul Scherrer Institute (PSI) participates in an international collaboration conducting such an experiment at the Institute Laue-Langevin in Grenoble. The experiment searches for evidence of ultracold neutrons disappearing into the mirror world. The first results have just been published in Physical Review Letters and indicate that under optimum escape conditions, the neutrons take longer than 100 s to disappear, if they do so at all. Future measurements planned at a new ultracold neutron source at PSI in Villigen (Switzerland) will allow a refinement of that value, and help constrain the theories which predict the existence of the mirror world.


Manfred Daum; manfred.daum@psi.ch, Telephone +41 56 310 36 68;

Klaus Kirch, klaus.kirch@psi.ch, Telephone +41 56 310 32 78

Further Information:

PRL article

Abstract (PDF)

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