The primary incoming cosmic rays (mostly protons) interact with air molecules high up in the atmosphere, about 10 km up. These interactions result in an extensive air shower consisting of an extremely large number of particles,mostly pions. Pion are bounds states of a quark and an anti-quark. They are the lowest mass particle that contains quarks, about ten times less massive than a proton or neutron, which is why they are the most plentifully produced. The charged pions live for only about 10 ns decaying to a muon and a neutrino. The muon is exactly like an electron except that its mass is about elementary100 time larger. Like the electron, it is an elementary particle. Since it doesn't contain quarks, it doesn't interact strongly but only by the electromagnetic interaction. As a result, most of the muons reach the ground before interacting. These are what are detected by your detector paddles.
One primary cosmic ray will therefore lead to a large number of muons reaching the ground. They will be spread out over an area approximately 1 km in diameter. These muons will hit the ground more or less simultaneously. Because of the difference in heights at which they are produced and there different path lengths to reach the ground, the arrive time will be spread out of a few micro seconds. By arranging, the detector paddles horizontally, we should find that two, or more, of them will be in coincidence some small fraction of the time. By determining this fraction, you will get a measure of the typical density of muons resulting from an extensive air shower.
| Delay Time: | 1.0 μs |
| Gate Width: | 2.0 μs |
| Channel Enable: | 1, 2, 3, 4 |
| Coincidence Level: | 1 |
This page is maintained by
Prof. Steve Schnetzer.