Neutron EDM

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Neutrons are an elemental part of the nucleus of the atom. Although electrically neutral overall, neutrons are made up of charged particles. The neutron electric dipole moment (nEDM) is a measure of the distribution of positive and negative charge inside the neutron - just as a magnet has north and south poles, so a neutron with an EDM would have one end slightly negative, and the other slightly positive. However, this can only happen if certain symmetries in the laws of physics are slightly broken - by exactly the same mechanisms that were responsible for the dominance of matter over anti-matter in the Universe at the time of the Big Bang. These mechanisms are not understood, but by measuring (and putting limits upon) the nEDM, we put extremely tight constraints upon new models of physics that attempt to explain the origin of all of the matter in the Universe. Our group currently holds the world's best limit in the precision of measurement of this fundamental quantity. The proposed work will improve the sensitivity by a factor of two in the first instance, and later on by much more - perhaps approaching an order of magnitude.