A scintillator-based detection system, of the type employed in the popular muon-lifetime instructional lab experiment, is used to measure the muon mass. The photomultiplier pulse pairs produced by the decay of cosmic ray muons into product electrons and positrons within the scintillator are detected by a digitizing oscilloscope and the energies of the product particles are quantified by integrating the area under their associated pulses. The observed distribution of product-particle energies is then compared with Monte Carlo simulated distributions assuming different values of the muon mass mμc2, where the modeling of product-particle energy loss within the scintillator accounts for collisional and radiative effects in a detailed way. Via a least-squares comparison, it is found that the simulated distribution based on a value of mμc2=105±5 MeV most closely matches the experimental distribution.

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Our scintillation detector was designed, constructed, and tested by Eljen Technology in Sweetwater, Texas USA.
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LabVIEW data-taking program is available from the authors upon request.
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See supplementary material at http://dx.doi.org/10.1119/1.4984811 for the Mathematica code and a reference manual.
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This quoted value of Ee assumes a massless product electron. Our simulation actually accounts for the product's non-zero rest mass, which modifies the value of Ee slightly.
22.
See the “
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Supplementary Material

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