A value of (-6.1 +/- 0.9(stat) +/- 0.5(syst)) x 10(-3) is obtained for the
quadratic slope parameter h in the K-L --> 3 pi (0) decay Dalitz plot at th
e NA48 experiment at the CERN SPS. The result is based on 14.7 x 10(6) full
y reconstructed K-L --> 3 pi (0) --> 6 gamma decays. This is the most preci
se measurement of any of the Dalitz plot slope parameters in the charged an
d neutral kaon decays so far. (C) 2001 Published by Elsevier Science B.V.