Speaker
Description
The NA62 experiment at CERN took data in 2016–2018 with the main goal of measuring the K+ → π+νν ̄ decay. The NA62 dataset is also exploited to search for light feebly interacting particles produced in kaon decays. Searches for K+ → e+N, K+ → μ+N and K+ → μ+νX decays, where N and X are massive invisible particles, are performed by NA62. The N particle is assumed to be a heavy neutral lepton, and the results are expressed as upper limits of O(10−8) of the neutrino mixing parameter |Uμ4|2. The X particle is considered a scalar or vector hidden sector mediator decaying to an invisible final state. Upper limits of the decay branching fraction for X masses in the range 10–370 MeV/c2 are reported. An improved upper limit of 1.0 × 10−6 is established at 90% CL on the K+ → μ+ννν branching fraction. Dedicated trigger lines were employed to collect di-lepton final states, which allowed establishing stringent upper limits on the rates lepton flavor and lepton number violating kaon decays. Upper limits on the rates of several K+ decays violating lepton flavour and lepton number conservation, obtained by analysing this dataset, are presented.
