Lattice QCD calculations have reached the percent level of uncertainty on several observables entering precision tests of the Standard Model.

Prominent examples are the hadronic vacuum polarisation contribution to the muon $(g-2)$, as well as the leptonic decay rates of pseudoscalar mesons, which are needed to extract values of CKM matrix elements. At this level of precision, isospin-breaking effects become important. They consist of strong isospin breaking (unequal up and down quark masses) and the coupling of quarks to photons (QED effects). Since the masses of hadrons that are stable under QCD+QED need to be computed in order to calibrate the bare parameters of QCD, the isospin-breaking effects on these masses are just as important.

The scientific goals of the workshop are to:

(a) enable a focused exchange of ideas and experiences among practitioners in this field,

(b) define benchmarks that measure the merit of different methods,

(c) identify the most promising treatments of QED effects on the lattice.