Leading isospin breaking effects in the hadronic vacuum polarisation with open boundaries

Understand

We discuss leading isospin breaking effects in the hadronic vacuum polarisation required for the investigation of the hadronic contribution to $(g-2)_{\mu}$.

• The calculation proceeds by expanding the relevant correlation functions around the isosymmetric limit.
• Isosymmetric observables are evaluated on gauge ensembles with $N_{f}=2+1$, $O(a)$ improved Wilson fermions and open boundary conditions generated by the CLS effort.
• Particular emphasis is placed on the relevant quark-disconnected diagrams required for a complete treatment of leading isospin breaking effects in the valence quark sector.