Effective field theory approach to QED corrections in flavour physics

Abstract

Thanks to the accurate measurements performed at the low-energy facilities [1] and LHC, flavour physics of light quarks, especially the bottom quark, emerged on the precision frontier for tests of the standard model (SM) and in searches for new physics effects. On the theoretical side, short-distance perturbative higher-order QCD and electroweak corrections are under good control for many processes. Moreover, tremendous progress in lattice computations [2] allows achieving percent to even subpercent accuracy for long-distance nonperturbative quantities. This allows for the prediction of some key observables with unprecedented accuracy and in turn the determination of short-distance parameters like the elements of the quark-mixing matrix (CKM) in the framework of the SM. In view of these prospects, it is also desirable to improve the understanding and treatment of QED corrections, which are generally assumed to be small. Unfortunately not much new development has taken place in the evaluation of such corrections.