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First observation and study of the K ±  → π ± π 0 e + e decay

Research output: Contribution to Journal/MagazineJournal articlepeer-review

  • The NA48/2 Collaboration
<mark>Journal publication date</mark>10/01/2019
<mark>Journal</mark>Physics Letters B
Number of pages10
Pages (from-to)552-561
Publication StatusPublished
Early online date29/11/18
<mark>Original language</mark>English


The NA48/2 experiment at CERN reports the first observation of the K ± →π ± π 0 e + e decay from an exposure of 1.7×10 11 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 ± π 0 e + 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.