On the theory side the error budget is dominated by hadronic uncertainties, in particular uncertainties on predictions for vacuum polarisation effects due to the strong interaction. DiRAC has enabled the first-ever computation of these effects starting from first principles, i.e. from the Standard Model Lagrangian by allowing simulations of Lattice Quantum Chromodynamics including effects of Quantum Electrodynamics. In a series of papers [1-4] researchers from the Universities of Edinburgh and Southampton, together with their collaborators in the US, have developed the required theoretical understanding and the numerical and algorithmic techniques needed to complete their ambitious and state-of-the-art program. In Lattice Quantum Chromodynamics one performs the calculation by constructing a discrete four-dimensional space-time grid (the lattice) on which one numerically solves the QCD equations of motion. Such lattice QCD simulations are the only known method to address the above questions without having to rely on ad hoc assumptions. This type of computation crucially relies on access to the world’s fastest parallel supercomputers like DiRAC’s Extreme Scaling system.

There is still some way to go until a full theoretical computation will match experimental precision. The DiRAC researchers have however developed a method that allows to get very close to the required precision by combining complementary experimental data and their numerical simulations. It will be exciting to compare to new experimental results expected by end of 2018!