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Physicists lead the field in solving matter mystery of the Big Bang

December 10, 2003

A University of Sussex-led team of scientists is ahead in the race to solve one of the biggest mysteries of our physical world: why the Universe contains matter.

With the help of a new £2.3 million grant, the team is working on a project to make one of the most sensitive measurements ever of sub-atomic particles. The results, expected within six years, could finally help to explain the creation of matter in the aftermath of the Big Bang.

Physicist Dr Philip Harris, the leader of the Sussex group, says: "Although there are a couple of other teams in the world working in this same area, we're managing to stay ahead of them, and we are constantly striving to beat our own world record. This is all very exciting for us. With this new development, we are on the verge of a major breakthrough in our understanding of the very origin of matter in the Universe."

The question that has vexed scientists and astronomers for years is why there is more matter in the Universe than anti-matter. Both were formed at the time of the Big Bang, about 13.7 billion years ago. For every particle formed, an anti-particle should also have been formed. Almost immediately, however, the equal numbers of particles and anti-particles would have annihilated each other, leaving nothing but light. But a tiny asymmetry in the laws of nature resulted in a little matter being left over, spread thinly within the empty space of the Universe. This became the stars and planets that we see around us today.

The only way scientists can verify their theories to explain this anomaly is to study the corresponding asymmetry in sub-atomic particles. It has taken five decades of research to reach the stage where measurements of these particles, called neutrons, have become sensitive enough to test the very best candidate theories. Neutrons are electrically neutral, but they have positive and negative charges moving around inside them. If the centres of gravity of these charges aren't in the same place, it would result in one end of the neutron being slightly positive, and the other slightly negative. This is called an electric dipole moment and is the phenomenon that physicists have been working to find for the past 50 years.

Using a £2.3 million grant from the Particle Physics and Astronomy Research Council, the Sussex scientists are collaborating with physicists at the Rutherford Appleton Laboratory and the Universities of Oxford and Kure (in Japan) to develop a new apparatus to measure the electric dipole moment.

The apparatus is a type of atomic clock that uses spinning neutrons instead of atoms. It will apply 300,000 volts to a container storing neutrons in a bath of liquid helium, which is kept at a temperature just above absolute zero. The clock frequency will be measured through nuclear magnetic resonance. Once completed, the apparatus is predicted to be one hundred times more sensitive than its predecessor.

Sussex, University of