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

As cosmic rays collide with the Earth's atmosphere, they produce secondary particles, some of which being charged pions. These pions then decay into muons and muon neutrinos. Despite their short lifetime, they travel at relativistic speeds, allowing them to reach the surface of the Earth. Through the use of Multi-Pixel Photon Counters (MPPCs), a type of Silicon Photo-Multiplier (SiPM), these particles can be detected as they pass through plastic scintillators. By putting two scintillators in parallel and only recording a count when a signal is detected in both in an arbitrarily short timeframe (in coincidence), the angular distribution of these particles can be measured as a function of their zenith angle. In this instance, distributions were measured every 10 degrees from 0 to 90 degrees, then compared to a simulation of the same setup made in Geant-4 using data available from the Cosmic Ray Library. The simulation and experimental results both approximately followed the generally accepted cos² distribution, with an R² difference between them of 0.9932.