William P. Gammel edited section_Experiment_subsection_Muon_Decay__.tex  over 8 years ago

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Muons that are traveling down towards the earth can be detected by a scintillation detector. The scintillation detector contains a material that fluoresce when () by radiation. A photomultiplier can then be used to measure this fluoresce, thus indicating when a muon has entered the detector. It is important to remember that the detector will not only fluoresce when a muon it detected. Muon decay into a positron or an electron will also cause the detector to fluoresce as will almost any other radiation. A voltage discriminator can be used to screen out low energy events, but this alone will not eliminate all the background radiation.   \par The entire set-up of our experiment consisted of a plastic scintillator, a photomultiplier tube, and a signal amplifier. Muons which enter the scintillator () some energy to molecules that are present, thus exciting electrons in the molecule to higher energy states. The excited electrons then emit light before returning to their initial energy level. Then when a muon decays inside the scintillator, the newly formed electron will emit light as well. The time between the two light pulses is the measure of the muons lifetime. As was mentioned earlier, not all light pulses represent decay, thus some measures must be taken to filter out these () events. There are three main methods by which we can correct for unwanted (). The machine itself partially compensates for the issues by resetting its internal timer if it does not detect a successive signal after a initial pulse within (). It is assumed that if () then the muon did not decay within the scintillator. It should also be noted that the threshold potential of the discriminator was varied in order to determine the threshold voltage that would trigger the () of an event. The threshold voltage was set at () such that the muon counter gave a flux of (), which is what is predicted for muon flux around sea level. A computer software program called "Muon" also offers (), by employing an algorithm called () to remove () from the raw data times. After data was run through sift, it was loaded into Igor Pro where it was graphed and fit to a (). The mean muon lifetime as determined from our fit was (), and data was collected over a 5 day period, which was well within the range of the accepted value (). Furthermore we expect our mean muon lifetime to be slightly different from the accepted value since negative muons can interact with protons through the electroweak force, thus shortening their lifespan.  \par Relativistic time dialation could not be confirmed for our experiment, since we only chose to take take data at a single elevation, 190 ft above sea level. Nonetheless we were able to calculate a myriad of important () from our data.   \subsection{Gamma-Ray Spectroscopy}