paper

First Observation and Study of the $K^{\pm} \to I ¨ ^{\pm} I ¨ ^{0} e^{+} e^{-}$ Decay

arXiv:1809.02873 · doi:10.1016/j.physletb.2018.11.046

Abstract

The NA48/2 experiment at CERN reports the first observation of the $K^{\pm} \to I ¨ ^{\pm} I ¨ ^{0} e^{+} e^{-}$ decay from an exposure of $1.7 \times 1 0^{11}$ 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( $K^{\pm} \to I ¨ ^{\pm} I ¨ ^{0} e^{+} e^{-}) = (4.24 \pm 0.14) \times 1 0^{- 6}$ . 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.

15 pages, 4 figures, 1 table

First Observation and Study of the K±→I¨±I¨0e+e− Decay

Abstract

First Observation and Study of the $K^{\pm} \to I ¨ ^{\pm} I ¨ ^{0} e^{+} e^{-}$ Decay