%0 Journal Article %T Radiative corrections to K_{l3} decays %A V. Cirigliano %A M. Knecht %A H. Neufeld %A H. Rupertsberger %A P. Talavera %J Physics %D 2001 %I arXiv %R 10.1007/s100520100825 %X We present a complete calculation of the K_{l3} decays K^+ --> pi^0 l^+ nu_l and K^0 --> pi^- l^+ nu_l to O(p^4, (m_d-m_u) p^2, e^2 p^2) in chiral perturbation theory with virtual photons and leptons. We introduce the concept of generalized form factors and kinematical densities in the presence of electromagnetism, and propose a possible treatment of the real photon emission in K^+_{l3} decays. We illustrate our results by applying them to the extraction of the Kobayashi--Maskawa matrix element |V_{us}| from the experimental K^+_{e3} decay parameters. %U http://arxiv.org/abs/hep-ph/0110153v1