Super computer calculation predicts high energy physics with unprecedented precision

Physicists from the University of Southampton have used simulations on high performance computers to determine the properties of a fundamental particle with unprecedented precision.

Comparisons of the super computer calculation with data from international experiments could either confirm or challenge the Standard Model of Particle Physics, a long-established theory for fundamental particles and how they interact.

Researchers in the Southampton High Energy Physics (SHEP) theory group are working with international partners to predict the effects of magnetic fields on muons, an unstable subatomic particle with properties similar to an electron. Their calculation of the hadronic vacuum polarisation contribution to the muon anomalous magnetic moment is part of a Standard Model prediction that will be compared to the results of experiments taking place in the USA and Japan.

The group’s research paper has been accepted for publication in the prestigious journal Physical Review Letters and selected for the ‘Editors’ Suggestion’, which highlights papers that are “particularly important, interesting and well written”.

Dr Andreas Jüttner, a Principal Research Fellow in Physics and Astronomy, explains, “Over the last few decades physicists have developed a comprehensive understanding of theoretical physics, crowned by the discovery of the Higgs boson in 2012 and leading to the award of the 2013 Nobel Prize in Physics to Englert and Higgs. There is a lot of other evidence however that our current understanding is not the full picture of nature. Indeed, known matter only makes a few percent of the nature of the universe, so there is a lot left to explain.

“Our strategy has been to make precise theoretical predictions and confront them with precise experimental measurements. It’s really exciting since we managed to make our prediction before the experiment publishes new data early in 2019.”

The Southampton research team involved in the project received support from Andreas’ European Research Council Starting Grant and included postdoctoral researchers Dr Vera Gülpers, Dr Antonin Portelli and Dr Justus Tobias Tsang. They are working with partners at the University of Edinburgh, Columbia University, Brookhaven National Lab and the University of Connecticut.

The research has used a method called Lattice Quantum Chromodynamics (Lattice QCD). Its calculation is performed by constructing a discrete four-dimensional space-time grid, known as the lattice, to numerically solve the QCD equations of motion. Such lattice QCD simulations are the only known method to address certain questions without having to rely on ad hoc assumptions.

This type of computation crucially relies on access to the world’s fastest parallel supercomputers and this research has benefited from a computing time grant from DiRAC, Distributed Research utilising Advanced Computing.

Andreas adds, “We are looking forward to finding out whether the Standard Model of Particle Physics will be confirmed by experiments taking place this year, but if they disagree it will be the strongest possible indication that we have found new physics.”