Press release

• 31 March 2006

Sussex physicists celebrate first findings of major neutrino experiment

Physicists at the University of Sussex are celebrating the first findings of a major international experiment to understand one of the mysteries of the universe.

Drs Lisa Falk Harris and Philip Harris are among the scientists taking part in the Main Injector Neutrino Oscillation Search (MINOS), which is designed to study ghostly sub-atomic particles called neutrinos. Neutrinos are able to traverse the entire Earth without interacting with matter, but the experiment has provided confirmation that neutrinos do, in fact, have mass.

Now the work will focus on how three different types of neutrino are able to transform one into another.

The Sussex team were responsible for designing a system to measure energy emitted by colliding neutrinos for a specialised 5,400 ton underground detector. The experiment involved beaming neutrinos straight through the earth from Fermi National Accelerator Laboratory (Fermilab) in Chicago to the detector 450 miles away in Minnesota. It took the scientists 11 years to develop the detector and the beam was switched on last year.

Dr Falk Harris says the findings now shape the progress of further work. "Originally, neutrinos were thought to be mass-less, but we now know that that isn't the case. In addition, they exhibit the most extraordinary behaviour - due to a quirk of quantum mechanics, the fact that they have slightly different masses allows the three distinct types of neutrinos to transmute from one to another as they travel along. This so-called oscillation is the property that we'll be studying with unprecedented precision."

Neutrinos are vital to our understanding of the Universe, yet scientists know very little about them. The abundance of neutrinos in the universe, produced by stars and nuclear processes, may explain how galaxies formed and why antimatter has disappeared. Originally neutrinos were thought to have no mass, but previous experiments suggested that they can oscillate between the three types - a phenomenon which is only possible if they do have mass.

Dr Falk Harris adds; "Our results will set the scope for further studies of neutrinos for years to come, ultimately helping us to understand the formation of the universe."

The MINOS experiment includes about 150 scientists, engineers, technical specialists and students from 32 institutions in 6 countries. The U.S. Department of Energy provides the major share of the funding, with additional funding from the U.S. National Science Foundation and from the United Kingdom's Particle Physics and Astronomy Research Council.

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