Time evolution of decay spectrum in K0,K0→π+π−e+e−

We consider the decay K0 (K0)→π+π−e+e− of a neutral K meson prepared in a state of strangeness +1 (−1). The time evolution of the state produces remarkable time-dependent effects in the angular distribution of the π+π−e+e− system. These effects are correlated with the time-dependence of the photon polarization in the radiative decay K0 (K0)→π+π−γ. We study, in particular, the CP-odd, T-odd term in the distribution dΓ/dφ of the angle between the π+π− and the e+e− planes. We also give the spectrum in the case that the decaying meson is an incoherent mixture of K0 and K0, and discuss the case of KS regeneration in a KL beam.