'Law of nature' broken, say physicists

Posted by Emma Woollacott

Scientists at Brookhaven National Laboratory say they have broken one of the laws of nature.

For a fraction of a second at the Relativistic Heavy Ion Collider (RHIC), physicists created a symmetry-breaking bubble of space where parity no longer existed.

Parity states that the universe is neither right- nor left-handed — that the laws of physics remain unchanged when expressed in inverted coordinates.

In the early 1950s it was found that the weak force, responsible for nuclear radioactivity, breaks the parity law. However, the strong force, which holds together subatomic particles, was thought to conform.

But results from the STAR experiment at RHIC, a 2.4-mile-circumference particle accelerator, show something different.

By smashing together the nuclei of gold atoms, the team created a short-lived quark-gluon plasma, similar to that which existed just after the Big Bang. They hope to use it to learn more about how structure in the universe — from black holes to galaxies — may have formed out of the soup.

It was the massive magnetic field produced by the plasma — the strongest ever created — that alerted the physicists that one of nature's laws might have been broken.

"A very interesting thing happened in these extreme conditions," says Jack Sandweiss, Yale's Donner Professor of Physics. "Parity violation is very difficult to detect, but the magnetic field in conjunction with parity violation gave rise to a secondary effect that we could detect."

Sandweiss found that quarks of a like sign moved together: up quarks moved along the magnetic field lines, while down quarks traveled against them. That the quarks could tell the difference in directions suggested that symmetry had been broken.

The results were so unexpected that Sandweiss and his colleagues waited more than a year to publish them, searching for an alternative explanation.

Sandweiss stresses that the effect only suggests parity violation — it doesn't prove it — and he's decided to open up the research to scrutiny by other physicists.

"I think it's a real effect, but we'll know more in the upcoming years," he says.

Next, the team wants to run the experiment at lower collision energies to see if the apparent violation disappears.

If the effect proves to be real, it could help scientists understand  why the universe is dominated by ordinary matter today, when equal amounts of matter and antimatter were created by the Big Bang.