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Search for heavy neutral lepton production in K+ decays to positrons

Research output: Contribution to Journal/MagazineJournal articlepeer-review

Article number135599
<mark>Journal publication date</mark>10/08/2020
<mark>Journal</mark>Physics Letters B
Number of pages9
Publication StatusPublished
Early online date2/07/20
<mark>Original language</mark>English


A search for heavy neutral lepton (N) production in K+→e+Ndecays using the data sample collected by the NA62 experiment at CERN in 2017–2018 is reported. Upper limits of the extended neutrino mixing matrix element |Ue4|^2 are established at the level of 10^−9 over most of the accessible heavy neutral lepton mass range 144–462 MeV/c2, with the assumption that the lifetime exceeds 50 ns. These limits improve significantly upon those of previous production and decay searches. The |Ue4|^2 range favoured by Big Bang Nucleosynthesis is excluded up to a mass of about 340 MeV/c2.