Model independent measurement of the leptonic kaon decay K± → μ± νμe+e−

Abstract

The NA48/2 experiment at CERN collected a very large sample of charged kaon decays into multiple final states. From this data sample we have reconstructed about 1500 events of the very rare decay K± → μ±νμe+e− over almost negligible background in the region with M(e+e−) above 140 MeV, which is of great interest in Chiral Perturbation Theory. We present the Mee spectrum and a model-independent measurement of the decay rate for this region.