Do ultracold neutrons get a kick from nanoparticles?

Published in Physics World, 1 Oct 2013

Physicists in France and Russia claim to have evidence that explains why so-called ultracold neutrons (UCNs) escape their traps. The evidence suggests that the neutrons are being kicked out of the traps by collisions with floating nanoparticles and could help explain discrepancies in measurements of the neutron lifetime. However, not all scientists in the field find the evidence compelling.

UCNs are neutrons that have been cooled to less than 2 mK above absolute zero. At these temperatures the neutrons are moving so slowly that they would easily be overtaken by someone running at a moderate pace. UCNs bounce off most surfaces they come into contact with, regardless of their angle of incidence. This has allowed physicists to trap large numbers of UCNs in oversized “bottles” made of materials such as copper or stainless steel – where the neutrons can be studied. Neutrons experience all four forces – electromagnetism, the weak force, the strong force and gravity – which make them a comprehensive laboratory for tests of the Standard Model of particle physics. […]

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