A joint Fermilab/SLAC publication

Physicists get a supercomputing boost

11/20/15

Scientists have made the first-ever calculation of a prediction involving the decay of certain matter and antimatter particles.

Sometimes the tiniest difference between a prediction and a result can tell scientists that a theory isn’t quite right and it’s time to head back to the drawing board.

One way to find such a difference is to refine your experimental methods to get more and more precise results. Another way to do it: refine the prediction instead. Scientists recently showed the value of taking this tack using some of the world’s most powerful supercomputers.

An international team of scientists has made the first ever calculation of an effect called direct charge-parity violation—or CP violation—a difference between the decay of matter particles and of their antimatter counterparts.

They made their calculation using the Blue Gene/Q supercomputers at the RIKEN BNL Research Center at Brookhaven National Laboratory, at the Argonne Leadership Class Computing Facility at Argonne National Laboratory, and at the DiRAC facility at the University of Edinburgh.

Their work took more than 200 million supercomputer core processing hours—roughly the equivalent of 2000 years on a standard laptop. The project was funded by the US Department of Energy’s Office of Science, the RIKEN Laboratory of Japan and the UK Science and Technology Facilities Council.

The scientists compared their calculated prediction to experimental results established in 2000 at European physics laboratory CERN and Fermi National Accelerator Laboratory.

Scientists first discovered evidence of indirect CP violation in a Nobel-Prize-winning experiment at Brookhaven Lab in 1964. It took them another 36 years to find evidence of direct CP violation.

“This so-called ‘direct’ symmetry violation is a tiny effect, showing up in just a few particle decays in a million,” says Brookhaven physicist Taku Izubuchi, a member of the team that performed the calculation.

Physicists look to CP violation to explain the preponderance of matter in the universe. After the big bang, there should have been equal amounts of matter and antimatter, which should have annihilated with one another. A difference between the behavior of matter and antimatter could explain why that didn’t happen.

Scientists have found evidence of some CP violation—but not enough to explain why our matter-dominated universe exists.

The supercomputer calculations, published in Physical Review Letters 1 Standard Model prediction for direct CP violation in K→ππ decay, so far show no statistically significant difference between prediction and experimental result in direct CP violation.

But scientists expect to double the accuracy of their calculated prediction within two years, says Peter Boyle of the University of Edinburgh. “This leaves open the possibility that evidence for new phenomena… may yet be uncovered.”

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