Eur. Phys. J. C (2007) 52: 875-891
https://doi.org/10.1140/epjc/s10052-007-0456-7

Regular Article - Experimental Physics

Search for direct CP violating charge asymmetries in K^±→π^±π⁺π^- and K^±→π^±π⁰π⁰ decays

¹ Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE,, UK
² CERN, 1211, Genève 23, Switzerland
³ Joint Institute for Nuclear Research, Joliot-Curie 6, Moscow region, 141980, Dubna, Russian Federation
⁴ The Enrico Fermi Institute, The University of Chicago, Chicago, Illinois, 60126, USA
⁵ Department of Physics and Astronomy, University of Edinburgh, JCMB King’s Buildings, Mayfield Road, Edinburgh, EH9 3JZ, UK
⁶ Dipartimento di Fisica dell’Università e Sezione dell’INFN di Ferrara, 44100, Ferrara, Italy
⁷ Dipartimento di Fisica dell’Università e Sezione dell’INFN di Firenze, 50125, Firenze, Italy
⁸ Institut für Physik, Universität Mainz, 55099, Mainz, Germany
⁹ Department of Physics and Astronomy, Northwestern University, Evanston, Illinois, 60208-3112, USA
¹⁰ Dipartimento di Fisica dell’Università e Sezione dell’INFN di Perugia, 06100, Perugia, Italy
¹¹ Dipartimento di Fisica dell’Università, Scuola Normale Superiore e Sezione dell’INFN di Pisa, 56100, Pisa, Italy
¹² DSM/DAPNIA – CEA Saclay, 91191, Gif-sur-Yvette, France
¹³ Fachbereich Physik, Universität Siegen, 57068, Siegen, Germany
¹⁴ Dipartimento di Fisica Sperimentale dell’Università e Sezione dell’INFN di Torino, 10125, Torino, Italy
¹⁵ Institut für Hochenergiephysik, Österreichische Akademie der Wissenschaften, 10560, Wien, Austria
¹⁶ Istituto di Cosmogeofisica del CNR di Torino, 10133, Torino, Italy
¹⁷ Scuola Normale Superiore and INFN, 56100, Pisa, Italy
¹⁸ CERN, 1211, Genève 23, Switzerland
¹⁹ Centre de Physique des Particules de Marseille, IN2P3-CNRS, Université de la Méditerranée, Marseille, France
²⁰ Istituto di Fisica, Università di Modena, 41100, Modena, Italy
²¹ Istituto di Fisica, Università di Urbino, 61029, Urbino, Italy
²² Physikalisches Institut, Universität Bonn, 53115, Bonn, Germany
²³ SLAC, Stanford University, Menlo Park, CA, 94025, Stanford, USA
²⁴ UCLA, Los Angeles, CA, 90024, USA

^* e-mail: goudzovs@mail.cern.ch

Received: 12 July 2007
Revised: 18 September 2007
Published online: 1 November 2007

Abstract

A measurement of the direct CP violating charge asymmetries of the Dalitz plot linear slopes A_g=(g⁺-g^-)/(g⁺+g^-) in K^±→π^±π⁺π^- and K^±→π^±π⁰π⁰ decays by the NA48/2 experiment at CERN SPS is presented. A new technique of asymmetry measurement involving simultaneous K⁺ and K^- beams and a large data sample collected allowed a result of an unprecedented precision. The charge asymmetries were measured to be A^c _g=(-1.5±2.2)×10^-4 with 3.11×10⁹K^±→π^±π⁺π^- decays, and Aⁿ _g=(1.8±1.8)×10^-4 with 9.13×10⁷K^±→π^±π⁰π⁰ decays. The precision of the results is limited mainly by the size of the data sample.