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±π0D as normalisation channel, the branching ratio is determined in a model-independent way to be Br(K± →π±e+e−γ, meeγ > 260 MeV/c^2) = (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
BALDINI, Wander;COTTA RAMUSINO, Angelo;DALPIAZ, Pietro;FIORINI, Massimiliano;GIANOLI, Alberto;PETRUCCI, Ferruccio Carlo;SAVRIE', Mauro;
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±π0D as normalisation channel, the branching ratio is determined in a model-independent way to be Br(K± →π±e+e−γ, meeγ > 260 MeV/c^2) = (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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