Effect of unitarization on the amplitudes for the decays K 1 0 → π+π− and K + → π+π+π−

Abstract

The unitarization of the amplitude for the decay process K 1 0 → 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.