On the electron-positron energy asymmetry in K_L --> pi0 e+ e-

Motivated by some new experimental and theoretical efforts, we update the theoretical analysis of the electron-positron energy asymmetry, which arises, in K_L --> pi0 e+ e-, from the two-photon intermediate state in the standard model. It is found that the measurement of this asymmetry in future experiments may increase our understanding of the K_{L, S} --> pi0 e+ e- decays, which would thus provide some useful information on quark flavor physics. Meanwhile, in the standard model the electron-positron energy asymmetry in the decay of K_S --> pi0 e+ e- is expected to be vanishingly small, therefore the asymmetry in K_S --> pi0 e+ e- might be a very interesting quantity to explore new physics scenarios.