Search for long-lived particles decaying to e^± μ^∓ ν

Long-lived particles decaying to e^±μ^∓ν, with masses between 7 and 50GeV/c² and lifetimes between 2 and 50ps, are searched for by looking at displaced vertices containing electrons and muons of opposite charges. The search is performed using 5.4fb^-1 of pp collisions collected with the LHCb detector at a centre-of-mass energy of √s=13TeV. Three mechanisms of production of long-lived particles are considered: the direct pair production from quark interactions, the pair production from the decay of a Standard-Model-like Higgs boson with a mass of 125GeV/c², and the charged current production from an on-shell W boson with an additional lepton. No evidence of these long-lived states is obtained and upper limits on the production cross-section times branching fraction are set on the different production modes.