Muon Decay Experiment John Klumpp And Ainsley Niemkiewicz

What Are Muons? Fundamental particles Carry charge of +/- 1 Essentially heavy electrons Inherently unstable Decay into electrons and neutrinos

Where Do They Come From? Cosmic rays collide with matter in the upper atmosphere Many fundamental particles produced Only muons make it to the surface. Why? -High mass -Time dilation

What Does Relativity Have To Do With It? Muons only survive about 2.2μs in lab frame 2.2μs * Speed of Light =.66 meters But the muons are not in the lab frame From the lab frame their clocks run slower, so they live longer From the muon’s reference frame the distance is shorter Measuring lifetimes confirms theory of relativity

How Do We Detect Them? Muons captured in scintillation detector Flash of light produced when muons are stopped

How Do We Measure Lifetime? Another flash of light is produced by detector when muon decays Time between capture flash and decay flash is the muon lifetime

How Do We Calculate Mean Lifetime Muons decay randomly, so many samples are needed Collect samples for 48 hours Fit data to exponential decay equation

Data Calibration  40 channels = 1.28 μs Compress data from 512 channels to 64 channels. This helps MatLab’s Gaussian approximation work better  10 channels = 1.28 μs Trial 1 (48 hour trial): F(x) = 172.9e-x/ channels Trial 2 (12 hour trial): F(x) = 109.4e-x/ channels

Fit Curve

Where’s The Mean Lifetime? The exponential decay equation is In this equation, b is the average lifetime. In trial 1, b = channels*1.28µs/40 channels = 2.38±0.13µs Similarly, in trial 2, b = 74.37*1.28/40 = 2.29±0.13µs

Sources of Uncertainty Background radiation Some muons don’t decay Some decays may not be detected Deletion of first fifteen channels

Conclusion Simple, accurate experiment Demonstrates random nature of particle decay Confirms relativistic time dilation