Measurement of the quadratic slope parameter in the KL-->3 pi 0 decay Dalitz plot.

A value of (−6.1 ± 0.9stat ± 0.5syst) × 10 is obtained for the quadratic slope parameter h in the KL → 3π decay Dalitz plot at the NA48 experiment at the CERN SPS. The result is based on 14.7 × 10 fully reconstructed KL → 3π → 6γ decays. This is the most precise measurement of any of the Dalitz plot slope parameters in the charged and neutral kaon decays so far. 1 Present address: High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, 305-0801, Japan 2 Present address: EP, CERN, CH-1211, Geneva 23, Switzerland 3 Based at Rutherford Appleton Laboratory, Chilton, Didcot,OX11 0QX, U.K 4 Present address: NIKHEF, PO Box 41882, 1009 DB Amsterdam, The Netherlands 5 Funded by the U.K. Particle Physics and Astronomy Research Council 6 On leave from Sezione dell’INFN di Firenze, I-50125 Firenze, Italy 7 Present address: SLAC, Stanford, CA 94309, USA 8 Present address: Carnegie Mellon University, Pittsburgh, PA 15213, USA 9 Dipartimento di Fisica dell’Universita’ di Modena e Reggio Emilia, via G. Campi 213/A I-41100 Modena, Italy 10 Funded by the German Federal Minister for Research and Technology (BMBF) under contract 7MZ18P(4)-TP2 11 Funded by Institut National de Physique des Particules et de Physique Nucléaire (IN2P3), France 12 Funded by the German Federal Minister for Research and Technology (BMBF) under contract 056SI74 13 Supported by the KBN under contract SPUB-M/CERN/P03/DZ210/2000 and computing resources of the Interdisciplinary Center for Mathematical and Computational Modeling of the University of Warsaw