Using the full data set of the NA48/2 experiment, the decay K± → π± e+ e- γ is observed for the first time, selecting 120 candidates with 7.3 ± 1.7 estimated background events. With K± → π± πD0 as normalisation channel, the branching ratio is determined in a model-independent way to be Br (K± → π± e+ e- γ, me e γ > 260 MeV / c2) = (1.19 ± 0.12stat ± 0.04syst) × 10-8. This measured value and the spectrum of the e+ e- γ invariant mass allow a comparison with predictions of chiral perturbation theory.
First Observation and Measurement of the Decay K+- ---> pi+- e+ e- gamma
ANZIVINO, Giuseppina;NAPPI, Aniello;VALDATA, Marisa
2008
Abstract
Using the full data set of the NA48/2 experiment, the decay K± → π± e+ e- γ is observed for the first time, selecting 120 candidates with 7.3 ± 1.7 estimated background events. With K± → π± πD0 as normalisation channel, the branching ratio is determined in a model-independent way to be Br (K± → π± e+ e- γ, me e γ > 260 MeV / c2) = (1.19 ± 0.12stat ± 0.04syst) × 10-8. This measured value and the spectrum of the e+ e- γ invariant mass allow a comparison with predictions of chiral perturbation theory.File in questo prodotto:
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