Can we probe right-handed charged quark currents?

Different scenarios of new physics beyond the standard model give rise to a direct coupling of right-handed quarks to W bosons. We will discuss how the prediction of the Callan-Treiman low energy theorem for the scalar K pi form factor in combination with recent data on $K^L_{\mu 3}$ decays can serve as a stringent test of the standard model (SM) and possible extensions, in particular right-handed charged quark currents (RHCs). In addition, we will comment on the impact of hadronic tau decay data on RHCs.