Muon Lifetime Experiment
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Brief
Explanation about this experiment... The muons contained in the flux of cosmic rays that rain down on us from the heavens are unstable particles with a lifetime of a few microseconds. There are a number of ways to observe this decay and measure the lifetime of these particles and we have setup a detector arrangement to do this in our laboratory. The principal behind this measurement is to use an absorber to stop these particles and then to observe the time difference between the stopping of the muon and the subsequent emission of its decay electron. By measuring the time between these two events we can observe the characteristic decay lifetime of these stopping muons. The detector setup consists of two sets of scintillation detectors located above and below a stack of plastic absorber material. A stopping muon will be signaled by a set of “in time” signals from the two scintillation counters above the absorber and “no signal” being observed in the two lower counters. When such an event happens we will then trigger the data acquisition system to record the signal coming from all of the 4 counters in the system. A decaying muon will have a second set of pulses detected in either the top or the bottom sets of counters following some time after muon had stopped in the absorber material. The lifetime of the stopping muons can then be seen directly by looking at the frequency of the secondary hits in the time interval from 0-10 microseconds following a muon stopping. The figures below show some sample events taken with the data acquisition system, a photo of some of the detector elements and the detector layout for this measurement.
Figure 2. This is a set of signals recorded using the setup of four scintillation counters described above. Each trace represents the time development of the signals from a given detector. The “stopping muon” signature can be seen to the left where there are two signal in the top two traces in coincidence with nothing appearing in the detectors below( around t=1000 nsec). This is then followed by a second set of pulses in the bottom two counters around t = 3000 nsec.
Figure 3. This is a set of signals recorded using the setup of four scintillation counters described above. Each trace represents the time development of the signals from a given detector. The “stopping muon” signature can be seen to the left where there are two signal in the top two traces in coincidence with nothing appearing in the detectors below( around t=1000 nsec). This is then followed by a second set of pulses this time in the top two counters around t = 3500 nsec. Figure 4. This is a set of signals recorded using the setup of four scintillation counters described above. The “stopping muon” signature can be seen to the left where there are two signal in the top two traces in coincidence with nothing appearing in the detectors below( around t=1000 nsec). This is then followed by a second set of pulses in all four counters around t = 8000 nsec. This is an example of a stopping muon signal followed by a second through going muon signal in the system. This is one of the backgrounds to this measurement.
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