A search for heavy neutral leptons has been performed with the ArgoNeuT detector exposed to the NuMI neutrino beam at Fermilab. We search for the decay signature N→νμ+μ-, considering decays occurring both inside ArgoNeuT and in the upstream cavern. In the data, corresponding to an exposure to 1.25×1020 POT, zero passing events are observed consistent with the expected background. This measurement leads to a new constraint at 90% confidence level on the mixing angle |UτN|2 of tau-coupled Dirac heavy neutral leptons with masses mN=280-970 MeV, assuming |UeN|2=|UμN|2=0.
ASJC Scopus subject areas
- General Physics and Astronomy