Measurement of the CP-Violation Parameterη+−γin Neutral Kaon Decays

Interference between K(S) and K(L) decays into the final state pi+pi-gamma has been observed in experiment 731 at Fermilab. By fitting the distribution of decays downstream of a regenerator, a new CP-violation parameter eta+-gamma, analogous to eta+-, has been measured, with its magnitude equal to (2.15 +/- 0.26 +/- 0.20) x 10(-3), and phi+-gamma, the associated phase angle, equal to (72 +/- 23 +/- 17)degrees. Assuming that any difference between this fit value for eta+-, and the previously measured value for eta+- can be attributed to direct CP violation in this decay, a limit of \epsilon'+-gamma\/epsilon < 0.3 at the 90% confidence level has been made.