A measurement of the neutral kaon semileptonic decay parameters

The CPLEAR experiment tests the CP, T and CPT symmetries by measuring the $K^0$ and $\overline{K}^0$ time dependent decay asymmetries. Data taking is in progress with a fully operational detector. The main point in the selection of semileptonic decays is to identify the lepton tracks. A high efficiency and low background was achieved using two Neural Networks trained with electron, positron and charged pion tracks. From the data acquired by CPLEAR between 1990 and 1992, and part of 1993, 275K events were selected as semileptonic neutral kaon decays with low background. In the results from this work the first error is statistical and the second systematic.