UC Santa Cruz

Long-lived particles decaying to e±μ∓ν$${e ^\pm } {\mu ^\mp } { u } $$, with masses between 7 and 50GeV/c2$$50 \,\text {GeV/}c^2 $$ and lifetimes between 2 and 50ps$$50 \,\text {ps} $$, are searched for by looking at displaced vertices containing electrons and muons of opposite charges. The search is performed using 5.4fb-1$$5.4 \,\text {fb} ^{-1} $$ of p$$p $$p$$p $$ collisions collected with the LHCb detector at a centre-of-mass energy of s=13TeV$$\sqrt{s} = 13 \,\text {TeV} $$. 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 125GeV/c2$$125 \,\text {GeV/}c^2 $$, and the charged current production from an on-shell W$$W $$ 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.