UCSC Abstract 2014 - Muon Speed Analysis

C. Woods, K. Natividad, J. Rathmann-Bloch

This experiment sought to evaluate the speed of muons by placing scintillators apart and measuring how long of a delay existed between each individual scintillator's triggering. It used the Quarknet DAQ's high-precision clock to confirm trigger differences as low as 1.25 nanoseconds.

Cosmic rays from space penetrate the Earth's atmosphere, and upon interacting, produce pions and kaons, which then decay into muons and other particles. We can detect these muons at the Earth's surface using scintillators and photo-multiplier tubes. Because the muons have vastly different energies, we initially thought that there might be an interesting distribution of their speeds. However, after conducting some background research, we realized that the energy differences we would see had little to no effect on the speed. We placed two detectors seven feet apart vertically and used four-fold coincidences to measure the time difference between the top and bottom detectors. The muons we detected were all traveling extremely close to the speed of light, approximately one foot per nanosecond, thus confirming our hypothesis.