A precise measurement of the direct CP violation

The direct CP violation parameter Re(ε/ε) has been measured from the decay rates of neutral kaons into two pions using the NA48 detector at the CERN SPS. With 3.3 million KL → π0π0 events collected during the 1998 and 1999 running periods, a result of Re(ε/ε) = (15.0 ± 2.7)×10−4 has been obtained. The result combined with the published 1997 sample is Re(ε/ε) = (15.3± 2.6)×10−4. 1) Present address: Oliver Lodge Laboratory, University of Liverpool, Liverpool L69 7ZE, U.K. 2) Present address: High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, 305-0801, Japan. 3) Present address: EP Division, CERN, 1211 Genève 23, Switzerland. 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) On leave from Österreichische Akademie der Wissenschaften, Institut für Hochenergiephysik, A-1050 Wien, Austria. 9) On leave from Joint Institute for Nuclear Research, Dubna, 141980, Russian Federation. 10) Present address: University of Alberta, Edmonton Alberta T6G 2J1, Canada. 11) Dipartimento di Fisica e INFN Bologna, viale Berti-Pichat 6/2, I-40127 Bologna, Italy. 12) Dipartimento di Fisica dell’Universita’ di Modena e Reggio Emilia, via G. Campi 213/A I-41100, Modena, Italy. 13) Instituto di Fisica Universitá di Urbino 14) Funded by the German Federal Minister for Research and Technology (BMBF) under contract 7MZ18P(4)-TP2. 15) Funded by Institut National de Physique des Particules et de Physique Nucléaire (IN2P3), France 16) Present address: Dipartimento di Fisica dell’Universitá di Roma “La Sapienza” e Sezione INFN di Roma, I-00185 Roma, Italy. 17) Funded by the German Federal Minister for Research and Technology (BMBF) under contract 056SI74. 18) Supported by the Committee for Scientific Research grants 5P03B10120, 2P03B11719 and SPUBM/CERN/P03/DZ210/2000 and using computing resources of the Interdisciplinary Center for Mathematical and Computational Modelling of the University of Warsaw. 19) Funded by the Austrian Ministry of Education, Science and Culture under contract GZ 616.360/2-IV GZ 616.363/2-VIII, and by the Fund for Promotion of Scientific Research in Austria (FWF) under contract P08929-PHY.