Supercomputers help explain mass

University researchers have helped use supercomputers to shed light on the behaviour of key sub-atomic particles.

The development could help explain why there is almost no anti-matter in the universe.

Scientists including physicists from the Universities of Edinburgh and Southampton have reported a landmark calculation of the decay of an elementary particle called a kaon, using breakthrough techniques on some of the world’s fastest supercomputers.

The calculation took 54 million processor hours on the IBM BlueGene/P supercomputer at the Argonne Leadership Class Facility at Argonne National Laboratory in the US.

Part of the analysis was performed on the DiRAC Cluster at the University of Edinburgh and the Iridis Cluster at the University of Southampton.

Fundamental process

The process by which a kaon decays into two lighter particles known as pions was explored in a 1964 Nobel Prize-winning experiment.

This revealed the first experimental evidence of a phenomenon known as charge-parity violation — a lack of symmetry between particles and their corresponding antiparticles.

This lack of symmetry may explain why the Universe is made of matter, and not antimatter.

Modelling the problem

With this dramatic boost in computing power we can get a more accurate and complete version of the present calculation, and other important details will come within reach.

Dr Peter BoyleSchool of Physics and Astronomy

When kaons decay into lighter pions, the constituent sub-particles known as quarks undergo changes brought about by weak forces that operate at such a small scale.

As the quarks move away, they exchange gluons - particles that cause the quarks to bind into the pions.

The computations are performed using a technique in which the decay is entered into a computer as a finite grid of space-time points.

The problem of calculating the decay rate can be reduced to a statistical method, called the Monte Carlo method.

Work in progress

The calculation marks the beginning of the next phase of the collaboration’s work.

This will involve improving the precision of the computations and extending the range of physical quantities for which the effects of the strong nuclear force can be quantified.

Comparing experimental measurements of rare processes with the predictions of the standard model is a powerful tool to search for signatures of new physics and in discriminating between proposed theories.

Computing power

The next generation of IBM supercomputers is being installed in many research centres around the world.

These include the Blue-Gene/Q at Edinburgh, part of the DiRAC facility of which both the Edinburgh and Southampton groups are members.

Supercomputers are also coming online at Argonne National Laboratory, the KEK laboratory in Japan, the Brookhaven National Lab and the Riken Brookhaven Research Center in the US.

These new IBM BlueGene/Q machines are expected to have 10 to 20 times the performance of the current machines.

International expertise

The project was carried out by physicists from the Brookhaven National Laboratory, Columbia University, the University of Connecticut, the Max-Planck-Institut für Physik, Riken Brookhaven Research Center, the University of Southampton and Washington University.

The calculations were performed on the Intrepid BlueGene/P supercomputer in ALCF at Argonne National Laboratory and on the Ds Cluster at Fermi National Laboratory.

The research was supported by DOE’s Office of Science, the UK’s Science and Technology Facilities Council, the University of Southampton, and the RIKEN Laboratory in Japan.

This is a nice synergy between science and the computer — the science pushing computer developments and the advanced computers pushing science forward, to the benefit of the science community and also the commercial world.

Dr Peter BoyleSchool of Physics and Astronomy