Scientists make antimatter research breakthrough

Scientists have made a research breakthrough that helps to explain why the universe we live in exists at all.

To date, we have lacked an explanation of why our universe is dominated by matter rather than containing equal parts matter and antimatter.

But particle physicists from the UK and around the world believe their research, called the BaBar experiment, conducted at the Stanford Linear Accelerator Centre (SLAC) in the US, demonstrates a dramatic difference in the behaviour of matter and antimatter that would explain why matter dominates.

Dan Bowerman, a member of the BaBar team from Imperial College London, said: "When the universe began with the big bang, matter and antimatter were created in equal amounts.

"However, all observations indicate that we live in a universe made only of matter. So what happened to the antimatter? The work at BaBar is bringing us closer to answering this question."

Experiments with SLAC's PEP-II particle accelerator have produced exotic particle and antiparticle pairs known as B and anti-B mesons. These rare forms of matter and antimatter are short-lived, decaying in turn to other, lighter subatomic particles known as kaons and pions, which can be seen in the BaBar experiment.

"If there were no difference between matter and antimatter, both the B meson and the anti-B meson would exhibit exactly the same pattern of decays," explained Marcello Giorgi, spokesman for the BaBar project.

"However, our new measurement shows an example of a large difference in decay rates instead."

By sifting through the decays of more than 200 million pairs of B and anti-B mesons, experimenters have discovered striking matter/antimatter asymmetry.

"We found 910 examples of the B meson decaying to a kaon and a pion, but only 696 examples for the anti-B," added Giorgi.

"The new measurement is very much a result of the outstanding performance of SLAC's PEP-II accelerator and the efficiency of the BaBar detector. The accelerator is now operating at three times its design performance and BaBar is able to record about 98 per cent of collisions."

While other experiments have observed matter/antimatter asymmetries before, this is the first time a difference has been found by simple counting of the number of decays of B and anti-B mesons to the same final state.