1. Measurement of lifetime for muons captured inside nuclei

2. Content 1. Introduce of the muon capture
2. The difference of the free decay and captured decay
3. How to measure the capture event
4. The apparatus of this experiment
5. The analysis of this experiment
6. Summary

3. Introduce of the muon capture

4. Muonic atom 1. Muon entering the matter
2. Electromagnetic interactions
3. One electron is replaced by muon and transitions down to the muonic atom K-shell around sec

5. Muonic atom
Due to the relatively high mass of muon, the Bohr radius of muon is times smaller than electron orbit
Only negative charged muon can form muonic atom

6. Muon capture There are two process of muon capture : μ+p→n+ν μ+p→n+ν+γ
The process contains no charged particles in the results
The process is relatively fast
Only negative charged muon may be captured

7. The difference of the free decay and captured decay

8. About muon lifetime
Muon lifetime is a typical process of radioactive decay.
The radioactive decay is a random process, independent of the previous life of the particle.

9. Muon lifetime distribution
is a constant
“decay rate”
The number of
decayed muon
The number of
muons at time t
We call the muon lifetime is

10. The example of muon lifetime measurement

11. Muon captured lifetime distribution
The capture decay lifetime is also a radioactive decay.
Because of the relative short lifetime of capture process, the lifetime we measured will less than free decay lifetime.

12. How the muon capture affect the muon lifetime measurement
The free decay lifetime:
The capture decay lifetime:
Here the A and C are constants, B is the mean lifetime of freedecay, D is the mean lifetime of capture decay, E is the randomaccidental coincidence which produced by the noise.

13. The example of muon capture lifetime measurement

14. How to measure the capture event

15. How to measure the capture process
The two process of capture are:
μ+p→n+ν
μ+p→n+ν+γ
We can try to measure the n or γ-ray

16. Measuring the γ-ray
γ-ray are more efficiently detected by high Z materials.
To detect the γ-ray, the material’s cross sections of photoelectric and pair production must large compared to the compton scattering cross section
NaI is a good material to detect the γ-ray.

17. Measuring the neutron
The most common method to detect neutron is using another charged particles to replace the kinetic energy of neutron.
The neutron in the plastic scintillator or organic scintillator may have a strong probability to collide with the hydrogen's proton and transfer kinetic energy to the proton.

18. The apparatus of this experiment

19. The experiment flow chart

20. The detectors μ n p

21. Experiment setup

22. TDC flow chart

23. ADC flow chart

24. The good event nim timing chartμ n p

25. The cross event1 nim timing chart
particle

26. The cross event2 nim timing chart
particle

27. Muon flux The flux of sea level muons is almost
for horizontal detectors
For this experiment, the effective area of the detector is
The probability of two cosmic rays comes in 10 micro-sec is almost

28. The analysis of this experiment

29. The qualitative analysis of adc

32. The qualitative analysis of tdc

33. Cu target quantitative analysis

34. Fe target quantitative analysis

35. Al target quantitative analysis

36. Summary

37. The result
The average result
The experiment result