"Ghost particle" sized up by cosmologists
Cosmologists at UCL are a step closer to determining the mass of the elusive neutrino particle, not by using a giant particle detector, but by gazing up into space. Although it has been shown that a neutrino has a mass, it is vanishingly small and extremely hard to measure - a neutrino is capable of passing through a light year (about six trillion miles) of lead without hitting a single atom. New results using the largest ever survey of galaxies in the universe puts total neutrino mass at no larger than 0.28 electron volts - less than a billionth of the mass of a single hydrogen atom. This is one of the most accurate measurements of the mass of a neutrino to date. The research is due to be published in an upcoming issue of the journal Physical Review Letters, and will be presented at the Weizmann:UK conference at UCL on 22-23 June 2010. It resulted from the PhD thesis of Shaun Thomas, supervised by Prof. Ofer Lahav and Dr. Filipe Abdalla. Professor Ofer Lahav, Head of UCL's Astrophysics Group, said: 'Of all the hypothetical candidates for the mysterious Dark Matter, so far neutrinos provide the only example of dark matter that actually exists in nature.
