Shedding light on the MiniBoone Excess with Searches at the LHC

Abstract

The origin of the excess of low-energy events observed by the MiniBooNE experiment remains a mystery, despite exhaustive investigations of backgrounds and a series of null measurements from complementary experiments. One intriguing explanation is the production of beyond-the-Standard-Model particles that could mimic the experimental signature of additional $\nu_e$ appearance seen in MiniBooNE. In one proposed mechanism, muon neutrinos up-scatter to produce a new ``dark neutrino'' state that decays by emitting highly-collimated electron-positron pairs. We propose high-energy neutrinos produced from $W$ boson decays at the Large Hadron Collider as an ideal laboratory to study such models. Simple searches for a low-mass, boosted di-lepton resonance produced in association with a high-$p_\text{T}$ muon from the $W$ decay with Run 2 data would already provide unique sensitivity to a range of dark neutrino scenarios, with prompt and displaced searches providing complementarity. Looking farther ahead, we show how the unprecedented sample of $W$ boson decays anticipated at the HL-LHC, together with improved lepton acceptance would explore much of the parameter space most compatible with the MiniBooNE excess.