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Press release

  • 4 April 2008

Physics experiment ranked in UK's top three

Philip Harris inspects the helium lines on the neutron EDM apparatus.

Philip Harris inspects the helium lines on the neutron EDM apparatus.

A small experiment led by a team of University of Sussex scientists has been ranked amongst the UK's most important particle-physics projects.

Following a recent government reorganisation of the funding of basic science in the UK, the Sussex-led neutron electric dipole moment (nEDM) experiment, which looks to explain why the Big Bang created more matter than anti-matter in the Universe, is one of only three experiments to have been rated "high priority".

Professor Philip Harris, who heads the Sussex group, says: "The review found that every single one of the UK's particle-physics projects was carrying out first-rate science, and all were worthy of funding. To fall into the top category in this way is therefore a real coup, and an honour - as well as an acknowledgement of the important contribution that these small but beautifully precise experiments can make to our understanding."

The project's top rating, which puts it alongside Atlas and CMS, the two large UK-led experiments at CERN's Large Hadron Collider in Switzerland, guarantees funding by the Science and Technology Facilities Council, which carried out the review.

The team at Sussex, together with scientists from the Rutherford Appleton Laboratory, Oxford University, Kure University (Japan), and the Institut Laue Langevin in Grenoble, have been investigating the asymmetry between matter and anti-matter - in other words, how all the material in the Universe emerged from the Big Bang - by studying a 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," says Professor Harris. "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, giving rise to a pear-shaped particle. This is called an electric dipole moment , and it's intimately related to the cosmic asymmetry that gave us our matter-dominated Universe."

The team built a special type of atomic clock that uses spinning neutrons instead of atoms to make these measurements. The last EDM result showed that the distortion in the subatomic particles is far smaller than many of the origin-of-matter theories had previously predicted. "Surprisingly, if the neutron were enlarged to the size of the Earth, the distortion would still be less than the size of a bacterium," says Professor Harris.

Notes for editors

Press Office contacts: Jacqui Bealing and Maggie Clune 01273 678888,

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