Effect of unitarization on the amplitudes for the decays K10→ π+π- and K+→ π+π+π-

The unitarization of the amplitude for the decay process K10→ π+π- and allowance for the rescattering of final-state pions in the decay process K+→ π+π+π- make it possible to evaluate, by using the parameters extracted from data on K → 2π decays, the K+→ π+π+π- decay width. The result agrees with the experimental width value at a level of a few percent. Allowance for corrections for higher order terms of the momentum expansion of the amplitude for the decay process K+→ π+π+π- leads to the slope-parameter value of g++-th = 0.2182, which agrees with its experimental counterpart, g++-exp = 0.2154 ± 0.0035.