Nobel prize won for discoveries in particle physics

TWO Japanese citizens and an American won the 2008 Nobel Prize for physics for discoveries that help explain the behaviour of the smallest particles of matter.

American Yoichiro Nambu, 87, of the University of Chicago, won half of the 10 million kronor (€1.03m) prize for the discovery of a mechanism called spontaneous broken symmetry.

Makoto Kobayashi and Toshihide Maskawa of Japan shared the other half of the prize for discovering the origin of the broken symmetry that predicted the existence of at least three families of quarks (types of subatomic particles) in nature.

The academy said the trio “presented theoretical insights that give us a deeper understanding of what happens far inside the tiniest building blocks of matter”.

In physics, the idea of symmetry refers to a kind of equivalence. At the subatomic level, for example, you should not be able to tell whether you are watching events unfold directly or in a mirror, or running forward or backward. Particles should behave just like their alter egos, called antiparticles (who carry the opposite electric charge). If any of these rules is violated, the symmetry is broken.

One big broken symmetry arose immediately after the big bang, when just a tiny bit more matter than antimatter was created. Because these two kinds of particles annihilate each other when they meet, that excess of matter was responsible for seeding the universe.

Nambu introduced his description of spontaneous symmetry violation into particle physics in 1960.

Nambu’s theories now permeate the Standard Model of particle physics, which is the basic theory of how the universe operates.

In 1972, Kobayashi and Maskawa explained why an experiment eight years before had found that some subatomic particles called kaons failed to follow the rules of symmetry.

Their explanation predicted three unknown subatomic particles called quarks. Scientists discovered those predicted particles between 1974 and 1994.

Kobayashi and Maskawa also predicted that symmetry would be broken in the behaviour of other particles, called B-mesons. As early as 2001, scientists confirmed that prediction, too.

Nambu said: “I was surprised and honoured. I didn’t expect it. I’ve been told for many years that I was on the list [to get the award],” he said. “I had almost given up.”

The Japanese-born Nambu moved to the US in 1952 and is a professor at the Enrico Fermi Institute at the University of Chicago.

Kobayashi, 64, works for the High Energy Accelerator Research Organisation, or KEK, in Tsukuba, Japan. Maskawa, 68, is a physics professor at Kyoto Sangyo University in Kyoto. He also teaches at Nagoya University in his hometown in central Japan.

“I wasn’t expecting the prize,” Kobayashi said. “I’ve been only pursuing my interest.”