Transverse Muon Polarization in $K^{\pm}\to\pi^0\mu^{\pm}\nu$ Decay   Induced by the Two-Photon Final-State Interaction
  We calculate the transverse muon polarization in the decay $K^{\pm}\to\pi^0\mu^{\pm}\nu$ induced by the electromagnetic two-photon final-state interaction. For the central part of the Dalitz plot the typical value of this polarization is about $4\times 10^{-6}$. 
V.P. Efrosinin, I.B. Khriplovich, G.G. Kirilin, Yu.G.Kudenko