The Muon Veto System for the Eos Hybrid Neutrino Demonstrator

Eos is a hybrid neutrino detector designed to combine measurements of both Cherenkov and scintillation light within the same event. It achieves this by using 240 ultra-fast photomultiplier tubes (PMTs) with a transit time spread of a few hundred picoseconds and a 500 mega-sample-per-second data readout system, enhanced by spectral sorting with dichroicons. Initially, Eos operated with 20 tonnes of pure water, incrementally adding water-based liquid scintillators to the 4-ton inner fiducial volume. This approach allows Eos to determine the optimal scintillator fraction for reconstructing particle position, energy, and direction for both internal and external sources. The detector is currently situated on the surface at UC Berkeley, where it encounters a cosmic muon rate of approximately 4000 Hertz. Eos has a Muon Veto System that can trigger on and veto cosmic rays entering the detector. This presentation provides an overview of the Eos Muon Veto System, summarizes the high energy muon results, and discusses data collected both as a veto and a trigger to identify through-going and decaying muons within the detector.