Project at Daya Bay nuclear plant tries to unlock key to origin of the universe

A global project at the Daya Bay nuclear plant is trying to track down tiny, elusive particles

PUBLISHED : Sunday, 01 September, 2013, 12:00am
UPDATED : Sunday, 01 September, 2013, 6:11am

Scientists at the Daya Bay nuclear power plant - about 50 kilometres from Hong Kong - say new results they have recorded about ghostly particles called neutrinos may be a step towards solving some of the biggest mysteries of the universe.

The importance attached to the Daya Bay Reactor Neutrino Experiment, as the multinational physics project is called, can be gauged by the fact that the results were named among the top 10 science breakthroughs last year by Science Magazine.

Neutrinos are among the most abundant yet least understood fundamental particles in the universe. Scientists believe a knowledge of them is key to understanding the origin and history of the universe.

Finding them is not easy. They are similar to electrons, but are tiny, as their name implies, and lack an electrical charge. They have mass, but it is miniscule even compared with other subatomic particles.

Scientists say that to understand how they work, they must establish their mass - in other words, weigh them. This has never been done accurately.

Neutrinos are hard to find because of the very small chance they have of interacting with regular matter. For example, they can pass right through the earth without touching any other particles. Because they have no charge, they are unaffected by electromagnetic force. Detectors built to find them see only flashes of 10 to 15 a year.

The sun produces lots of neutrinos, but it is far away. While commercial nuclear reactors such as Daya Bay allow scientists to study these particles at close hand, it is still not an easy job.

Scientists know they have a weak nuclear force, existing in three forms or "flavours" - electron (a stable subatomic particle), muon and tau (unstable subatomic particles). In a process called neutrino oscillation, these change from one flavour to another over time. Each flavour has a corresponding particle called an anti-neutrino.

Neutrino oscillation makes the particles elusive: not only do they change form, but most of them just disappear. Such behaviour won them the name of "phantom particles".

Professor Kam-Biu Luk, a physicist at the University of California, Berkeley, who is a co-spokesman for the project, said the experiment's latest results were a step towards measuring the weight of neutrinos. "The evolution of the early universe depends on how heavy the neutrinos are," he said.

"We need to collect a great deal of data and measure the energy of the anti-neutrinos as precisely as we can to obtain these results."

Another co-spokesman, Dr Cao Jun, a researcher with the Chinese Academy of Sciences, agreed with Luk but added that sensitive sensors and supercomputers were only part of the reason Daya Bay had gained a lead in the race.

Facilities in South Korea and France were conducting similar experiments, Cao said. "We got the results before them, probably because we have a better understanding of our sensors. It helps us come up with an effective approach," he said.

But Cao said they were still far from knowing the exact weight of neutrinos. They are not even sure which kind of neutrino is the heaviest.

Cao said a new facility was planned for Jiangmen, Guangdong, to harvest neutrinos from two large nuclear plants.