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RESEARCH PRODUCT

Kaon Physics at CERN – Recent Results from the NA48/2 and NA62 Experiments

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This letter presents recent results from the kaon experiments NA48/2 and its successor NA62 at CERN. With samples of 2.5 × 106 K µ 3 ± and 4.0 × 106 K e 3 ± events collected by NA48/2 in 2004, precise measurements of the form factors were performed. The Chiral Perturbation Theory was tested through a new study of K ± → π± γγ decays based on data taken with minimal trigger conditions. Using the beam line and detector of NA48/2 in the years 2007-2008, NA62 performed a precison measurement of the helicitysuppressed ratio of the charged kaon leptonic decay rates K ± → e+ ν and K ± → μ + ν Using the full data set, which is about ten times larger than the previous world data sample, the total uncertainty on this ratio is only 0.4%, representing a precision test of μ – e lepton universality. Finally, the main stage of the NA62 experiment is presented. The planned measurement of the ultra rare decay K + → π+ at 10% precision will provide a powerful test of the Standard Model. The experimental challenges to reach this goal require new detectors with exceptional performances.