Kaon programme at CERN: recent results

Understand

Searches for lepton flavour and lepton number violation in kaon decays by the NA48/2 and NA62 experiments at CERN are presented.

• A precision measurement of the helicity-suppressed ratio RK of the K --> e nu and K --> mu nu decay rates has been performed using the full data set collected by the NA62 collaboration in 2007.
• The data sample amounted to 145,958 reconstructed K --> e nu candidates with 11.0% background contamination.
• The result is RK = (2.488 +- 0.010) X 10^{-5}, which is in agreement with the Standard Model expectation.