Background readout electronics. These particles can be either charged, like electrons or muons, artts The detector responds to any particle that produces enough scintillation light to trigger neutral, like photons, that produce charged particles when they interact inside the scintillator. Now, the detector has no knowledge of whether a penetrating particle stops or not inside the scintillator and so has no way of distinguishing between light produced by muons that stop and decay inside the detector, from light produced by a pair of through-going muons that occur one right after the other. This important source of background events can be dealt with in two ways. First, we can restrict the time interval during which we look for the two successive flashes of scintillator light characteristic of muon decay events. Secondly, we can estimate the background level by looking at large times in the decay time histogram where we expect few events from genuine muon decay Fermi Coupling Constant GE Muons decay via the weak force and the fermi coupling constant GF is a measure of the strength of the weak force. To a good approximation, the relationship between the muon lifetime t and gr is particularly simple 192兀3h Ge mc where m is the mass of the muon and the other symbols have their standard meanings Measuring t with this instrument and then taking m from, say, the Particle Data group (http://www.pdg.ibl.gov)producesavalueforGf. Muon physics10 Muon Physics Backgrounds The detector responds to any particle that produces enough scintillation light to trigger its readout electronics. These particles can be either charged, like electrons or muons, or neutral, like photons, that produce charged particles when they interact inside the scintillator. Now, the detector has no knowledge of whether a penetrating particle stops or not inside the scintillator and so has no way of distinguishing between light produced by muons that stop and decay inside the detector, from light produced by a pair of through-going muons that occur one right after the other. This important source of background events can be dealt with in two ways. First, we can restrict the time interval during which we look for the two successive flashes of scintillator light characteristic of muon decay events. Secondly, we can estimate the background level by looking at large times in the decay time histogram where we expect few events from genuine muon decay. Fermi Coupling Constant GF Muons decay via the weak force and the Fermi coupling constant GF is a measure of the strength of the weak force. To a good approximation, the relationship between the muon lifetime τ and GF is particularly simple: where m is the mass of the muon and the other symbols have their standard meanings. Measuring τ with this instrument and then taking m from, say, the Particle Data Group (http://www.pdg.lbl.gov) produces a value for GF. 192π 3
7 GF 2 m 5 c 4 τ =