Measurement of lifetime for muons captured inside nuclei

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Measurement of lifetime for muons captured inside
nuclei
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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

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Introduce of the muon capture
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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

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Muonic atom

• Due to the relatively high mass of muon, the Bohr
  radius of muon is 206.7 times smaller than
  electron orbit
• Only negative charged muon can form muonic atom

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Muon capture

• There are two process of muon capture
• µp?n?
• µp?n??
• The process contains no charged particles in the
  results
• The process is relatively fast
• Only negative charged muon may be captured

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The difference of the free decay and captured
decay
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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.

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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
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The example of muon lifetime measurement
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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.

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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.

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The example of muon capture lifetime measurement
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How to measure the capture event
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How to measure the capture process

• The two process of capture are
• µp?n?
• µp?n??
• We can try to measure the n or ?-ray

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Measuring the ?-ray

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

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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.

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The apparatus of this experiment
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The experiment flow chart
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The detectors
µ
n
p
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Experiment setup
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TDC flow chart
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ADC flow chart
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The good event nim timing chart
µ
n
p
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The cross event1 nim timing chart
particle
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The cross event2 nim timing chart
particle
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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

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The analysis of this experiment
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The qualitative analysis of adc
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The qualitative analysis of tdc
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Cu target quantitative analysis
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Fe target quantitative analysis
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Al target quantitative analysis
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Summary
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The result
The average result
The experiment result