First observation and study of the $K^\pm \to \pi^\pm \pi^0 e^+ e^-$ decay

J.R. Batley , G. Kalmus , C. Lazzeroni , D.J. Munday , M.W. Slater , S.A. Wotton , R. Arcidiacono , G. Bocquet , N. Cabibbo , A. Ceccucci , D. Cundy , V. Falaleev , M. Fidecaro , L. Gatignon , A. Gonidec , W. Kubischta , A. Maier , A. Norton , M. Patel , A. Peters , S. Balev , P.L. Frabetti , E. Gersabeck , E. Goudzovski , P. Hristov , V. Kekelidze , V. Kozhuharov , L. Litov , D. Madigozhin , M. Misheva , N. Molokanova , I. Polenkevich , Yu. Potrebenikov , S. Stoynev , A. Zinchenko , E. Monnier , E. Swallow , R. Winston , P. Rubin , A. Walker , P. Dalpiaz , C. Damiani , M. Fiorini , M. Martini , F. Petrucci , M. Savrié , M. Scarpa , H. Wahl , W. Baldini , A. Cotta Ramusino , A. Gianoli , M. Calvetti , E. Celeghini , E. Iacopini , M. Lenti , G. Ruggiero , A. Bizzeti , M. Veltri , M. Behler , K. Eppard , M. Hita-Hochgesand , K. Kleinknecht , P. Marouelli , L. Masetti , U. Moosbrugger , C. Morales Morales , B. Renk , M. Wache , R. Wanke , A. Winhart , D. Coward , A. Dabrowski , T. Fonseca Martin , M. Shieh , M. Szleper , M. Velasco , M.D. Wood , G. Anzivino , E. Imbergamo , A. Nappi , M. Piccini , M. Raggi , M. Valdata-Nappi , P. Cenci , M. Pepe , M.C. Petrucci , F. Costantini , N. Doble , L. Fiorini , S. Giudici , G. Pierazzini , M. Sozzi , S. Venditti , G. Collazuol , L. Dilella , G. Lamanna , I. Mannelli , A. Michetti , C. Cerri , R. Fantechi , B. Bloch-Devaux (1) , C. Cheshkov (1) , J.B. Chèze (1) , M. de Beer (1) , J. Derré (1) , G. Marel (1) , E. Mazzucato (1) , B. Peyaud (1) , B. Vallage (1) , M. Holder , M. Ziolkowski , S. Bifani , M. Clemencic , S. Goy Lopez , C. Biino , N. Cartiglia , F. Marchetto , H. Dibon , M. Jeitler , M. Markytan , I. Mikulec , G. Neuhofer , L. Widhalm

1 IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers

The NA48/2 experiment at CERN reports the first observation of the K±→π±π0e+e− decay from an exposure of 1.7×1011 charged kaon decays recorded in 2003–2004. A sample of 4919 candidates with 4.9% background contamination allows the determination of the branching ratio in the full kinematic region, BR(K±→π±π0e+e−)=(4.24±0.14)×10−6 . The study of the kinematic space shows evidence for a structure dependent contribution in agreement with predictions based on chiral perturbation theory. Several P- and CP-violating asymmetries are also evaluated.

Mots clés: K: secondary beam; K+: semileptonic decay; K-: semileptonic decay; perturbation theory: chiral; CP: violation; kinematics; K+: branching ratio: measured; K-: branching ratio: measured; background; asymmetry: CP; parity: violation; structure; CERN Lab; NA48; CERN SPS; experimental results; K+ --> pi+ pi0 electron positron; K- --> pi- pi0 electron positron; S010.120

Domaines: Physique des Hautes Energies - Expérience [hep-ex]

J.R. Batley, G. Kalmus, C. Lazzeroni, D.J. Munday, M.W. Slater, et al.. First observation and study of the $K^\pm \to \pi^\pm \pi^0 e^+ e^-$ decay. Phys.Lett.B, 2019, 788, pp.552-561. ⟨10.1016/j.physletb.2018.11.046⟩. ⟨hal-01880982⟩