Recent results on kaon decays by the NA48/2 experiment at CERN

• Published in: Hyperfine interactions 2016, Vol.237 (1), p.1-7, Article 108
• Main Authors: Bloch-Devaux, Brigitte, Venditti, Stefano
• Format: Article
• Language: English
• Subjects: 8-12 June 2015; Atomic; Canada; CERN; Condensed Matter Physics; Decay; Hadrons; Heavy Ions; Molecular; Nuclear Physics; Optical and Plasma Physics; Physics; Physics and Astronomy; Proceedings of the 6th International Symposium on Symmetries in Subatomic Physics (SSP 2015); Surfaces and Interfaces; Thin Films; Victoria
• ISSN: 0304-3843; 1572-9540
• DOI: 10.1007/s10751-016-1318-1

The NA48/2 experiment reports the first observation of the rare decay K ± → π ± π 0 e + e − , based on about 2000 candidates from 2003 data. The preliminary branching ratio in the full kinematic region is ℬ ( K ± → π ± π 0 e + e − ) = ( 4.06 ± 0.17 ) ⋅ 1 0 − 6 . A sample of 4.687 × 10 6 K ± → π ± π D 0 events collected in 2003/4 is analyzed to search for the dark photon ( A ′ ) via the decay chain K ± → π ± π 0 , π 0 → γ A ′ , A ′ → e + e − . No signal is observed, limits in the plane mixing parameter ε 2 versus its mass m A ′ are reported.