UMHEP-410 Reanalysis of the decay KL → π 0 e + e −

The decay KL → π0e+e− is being searched for as a signal of direct ∆S = 1 CP violation. We provide a thorough updating of the analysis of the three components of the decay: 1) Direct CP violation, 2) CP violation through the mass matrix and 3) CPconserving (two-photon) contributions. First the chiral calculation of the KS → π0e+e− rate, due to Ecker, Pich and de Rafael (EPR), is updated to include recent results on the nonleptonic amplitude. Then we systematically explore the uncertainties in this method. These appear to be so large that they will obscure the direct CP violation unless it is possible to measure the KS → π0e+e− rate. The CP-conserving amplitude remains somewhat uncertain, but present indications are such that there may be a sizable CPviolating asymmetry in the e+, e energies from the interference of the CP-conserving and CP-violating amplitudes and this may potentially be useful in determining whether direct CP violation is present.