Using MPPCs to Measure the Zenith Angle Dependence of Cosmic Ray Muons

Understanding cosmic rays is vital for studying astronomical events and high energy physics. Muons, the most abundant secondary cosmic rays at sea level, are ideal for studying cosmic ray interactions. We constructed a cosmic ray muon detector and used it to measure the angular distribution of atmospheric muons as a function of zenith angle. The detector was constructed using two plastic scintillators and Multi-Pixel Photon Counters (MPPCs) operated in coincidence mode. The experiment measured the muon rate at 10 different zenith angles ranging from 0 to 90 degrees at sea level for over 2 weeks. The experimental results were compared with results obtained from a Geant-4 simulation using input distributions from the Cosmic Ray Library. A cosine square distribution was found in both experimental and simulated data and the experimental vs simulated fits were found to be in strong agreement with a coefficient of determination value of 0.9932. The simulation and experimental results were found to differ significantly at angles higher than 60 degrees, which can be correlated with attenuation with the building which was not present in the simulation.