Isospin mass differences of the B, D and K.

We compute the electromagnetic mass difference for the B-, D- and K-mesons using QCD sum rules with double dispersion relations. For the B- and D-mesons we also compute the linear quark mass correction, whereas for the K the standard soft theorems prove more powerful. The mass differences, which have not previously been computed via a double dispersion, are fully consistent with experiment, albeit with large uncertainties. [ABSTRACT FROM AUTHOR]