Question

The following question is based on the lifetime of muon lab.

(i) The muons whose decays we observe are born outside the detector and therefore spend some (unknown)
portion of their lifetime outside the detector. So, we never measure the actual lifetime of any muon.
Yet, we claim we are measuring the lifetime of muons. How can this be? In addition to this, Why do the lifetimes of positive and negative muons differ?

(ii)The timeout interval for the experiment was found to be 20.02 microseconds. What does the timeout interval of the FPGA imply about the maximum time between signal pulses when conducting the lab? Please explain this part in detail.

(iii) Explain the behaviour of the muon rate reported by the software as the discriminator threshold and
HV setting are varied. (Note that during the experiment, the muon rate decreased for both) Why is this?

Answer 1

(1) Most muons detected are created about 15 km above Earth's surface, so on average they will have survived for some amount of time calculated using special relativity before reaching the detector.

The detector can be used to detect the lifetime of muon is a scintillator, so it detects when the muon enters the detector with a flash, then if the muon decays it detects another flash. The time between flashes is said to be the muon's lifetime.

So I think that the muon's lifetime the machine giving is not be   the actual lifetime (just the lifetime of it on Earth's surface) . As we have no hypothetical measurements for the lifetime of muon outside the detector so we are only measuring the value in the earths from not in the 15km above the earths frame.

If you consider a muon decay in vacuum then there is no difference between the lifetimes of muons and antimuons.

However a muon can interact with a proton via the weak force to form a neutron, while an antimuon cannot. Since the air is full of protons this means the muon lifetime in air is slightly shorter than the antimuon lifetime. If the air were full of antiprotons instead of protons the effect would be the other way round.