Long-lived particles decaying to e±μ∓ν, with masses between 7
and 50 GeV/c2 and lifetimes between 2 and 50 ps, are searched for by
looking at displaced vertices containing electrons and muons of opposite
charges. The search is performed using 5.4 fb−1 of pp collisions
collected with the LHCb detector at a centre-of-mass energy of s=13
TeV. 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 125 GeV/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