Effect of unitarization on the amplitudes for the decays K ⁰₁ → π⁺π⁻ and K ⁺ → π⁺π⁺π⁻

Abstract

The unitarization of the amplitude for the decay process K ⁰₁ → 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.