| Description |
The anomalous magnetic moment of the muon, au, is one of the most precisely measured quantities in Nature. It can also be calculated to a very high precision theoretically in the framework of the Standard Model. Interestingly, there is a persistent deviation of the theoretical value from the experimentally measured value at the level of of about three standard deviations. This discrepancy is a possible indication of the incompleteness of the Standard Model and sign of undiscovered, fundamental physical processes. Thus, it is of paramount importance to sharpen or resolve this uncertainty. On the experimental side, a new experiment is underway at the Fermi National Accelerator Laboratory with the aim of reducing the experimental uncertainty by a factor of four. A comparable reduction of the theoretical uncertainty is much desired. The anomalous magnetic moment receives contributions from all sectors of the Standard Model, including the electromagnetic, weak, and strong interactions. They have all been calculated with varying degrees of uncertainty. The largest theoretical uncertainty comes from the contribution from the strong-interaction sector, as described by quantum chromodynamics. In our study, we contribute to the improvement of the theoretical prediction using a numerical method based on lattice quantum chromodynamics (LQCD). In LQCD, this contribution can be expressed as a sum of two terms: a quark-line-connected part and a quark-line-disconnected part. We focus on the latter. We rst motivate our study, provide the theoretical background, review the theoretical calculation, brie y discuss the experiments, describe the algorithm and parameter tuning, and give the final result. |
