Search for long-lived particles decaying to [Formula omitted][Formula omitted][Formula omitted]

Long-lived particles decaying to [Formula omitted], with masses between 7 and [Formula omitted] and lifetimes between 2 and [Formula omitted], are searched for by looking at displaced vertices containing electrons and muons of opposite charges. The search is performed using [Formula omitted] of [Formula omitted] [Formula omitted] collisions collected with the LHCb detector at a centre-of-mass energy of [Formula omitted]. 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 [Formula omitted], and the charged current production from an on-shell [Formula omitted] 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.