Data di Pubblicazione:
2003
Abstract:
The K-L --> pi(+)pi(-)e(+)e(-) and K-S --> pi(+) pi(-) e(+) e(-) decay modes have been studied in detail using the NA48 detector at the CERN SPS. Based on the data collected during the 1998 and 1999 run periods, a sample of 1162 K-L --> pi(+) pi(-) e(+)e(-) candidates has been observed with an expected background level of 36.9 events, yielding the branching ratio measurement BR(K-L --> pi(+) pi(-) e(+) e(-)) = (3.08 +/- 0.20) x 10(-7). The distribution of events in the sinphicosphi variable, where phi is the angle between the pi(+)pi(-) and the e(+)e(-) decay planes in the kaon centre of mass, is found to exhibit a large CP-violating asymmetry with the value A(phi) = (14.2 +/- 3.6)%. For the K-s --> pi(+) pi(-) e(+) e(-) decay channel, 621 candidates have been identified in the 1999 data sample with an estimated background contribution of 0.7 event. The corresponding branching ratio has been determined to be BR(K-s --> pi(+)pi(-)e(+)e(-)) = (4.71 +/- 0.32) x 10(-5). The combined value of this measurement with the published 1998 result is BR(K-s --> pi(+) pi(-) e(+)e(-)) = (4.69 +/- 0.30) X 10(-5). No asymmetry is observed in this decay mode. Our results are in good agreement with theoretical predictions based on a phenomenological description of radiative kaon decays. The form factor parameters a(1)/a(2) and (g) over tilde (M1) in the K-L --> pi(+)pi(-)e(+)e(-) direct emission process as well as the value of the K-0 charge radius have been extracted from the data.
Tipologia CRIS:
03A-Articolo su Rivista
Keywords:
TIME-REVERSAL INVARIANCE; DIRECT CP VIOLATION; NA48 EXPERIMENT; ELECTROMAGNETIC TRANSITION; RADIATIVE-CORRECTIONS; TAGGING DETECTOR; NEUTRAL KAONS; CHARGE RADIUS; K-L->PI(+)PI(-)E(+)E(-); CERN
Elenco autori:
A. Lai;D. Marras;A. Bevan;R. S. Dosanjh;T. J. Gershon;B. Hay;G. E. Kalmus;C. Lazzeroni;D. J. Munday;M. D. Needham;E. Olaiya;M. A. Parker;T. O. White;S. A. Wotton;G. Barr;G. Bocquet;A. Ceccucci;D. Cundy;N. Doble;V. Falaleev;L. Gatignon;A. Gonidec;B. Gorini;G. Govi;P. Grafstrom;W. Kubischta;M. Lenti;S. Luitz;I. Mikulec;A. Norton;S. Palestini;B. Panzer-Steindel;H. Taureg;M. Velasco;H. Wahl;C. Cheshkov;A. Gaponenko;P. Hristov;V. Kekelidze;D. Madigojine;G. Tatishvili;Y. Potrebenikov;A. Zinchenko;I. Knowles;V. Martin;R. Sacco;A. Walker;M. Contalbrigo;P. Dalpiaz;J. Duclos;P. L. Frabetti;A. Gianoli;M. Martini;L. Masetti;F. Petrucci;M. Savrie;A. Bizzeti;M. Calvetti;G. Collazuol;G. Graziani;E. Iacopini;M. Veltri;H. G. Becker;M. Eppard;H. Fox;K. Holtz;A. Kalter;K. Kleinknecht;U. Koch;L. Kopke;P. L. da;P. Marouelli;I. Pellmann;A. Peters;S. A. Schmidt;V. Schonharting;Y. Schue;R. Wanke;A. Winhart;M. Wittgen;J. C. Chollet;L. Fayard;L. Iconomidou-Fayard;J. Ocariz;G. Unal;I. Wingerter-Seez;G. Anzivino;P. Cenci;E. Imbergamo;P. Lubrano;A. Mestvirishvili;A. Nappi;M. Pepe;M. Piccini;R. Casali;C. Cerri;M. Cirilli;F. Costantini;R. Fantechi;S. Giudici;I. Mannelli;G. Pierazzini;M. Sozzi;J. B. Cheze;J. Cogan;M. D. Beer;P. Debu;A. Formica;R. G. de;E. Mazzucato;B. Peyaud;R. Turlay;B. Vallage;M. Holder;A. Maier;M. Ziolkowski;R. Arcidiacono;C. Biino;N. Cartiglia;M. Clemencic;F. Marchetto;E. Menichetti;J. Nassalski;E. Rondio;M. Szleper;W. Wislicki;S. Wronka;G. Fischer;M. Jeitler;M. Markytan;G. Neuhofer;M. Pernicka;A. Taurok;L. Widhalm
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