Aydın, Zeki Zekeriya2020-02-172020-02-171973https://doi.org/10.1103/PhysRevD.7.3522http://hdl.handle.net/20.500.12575/69625It is shown with the help of the pion-gauge condition that the divergence of the most general boson current in K l 3 decay vanishes in the limit of zero four-momentum of the pion. This in turn implies ξ = − 1 at the (unphysical) point t = m 2 K . Inasmuch as ξ does not seem, experimentally, to vary much with t , the result is significant in the physical region and agrees with experimentenCC0 1.0 UniversalArticle7113522352505562821