How Do Positrons Reach Cloud Chambers Without Annihilating?

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SUMMARY

The discussion centers on the behavior of positrons in Anderson cloud chambers, specifically addressing how they can reach the chamber without annihilating upon contact with electrons. It is established that the probability of annihilation is low when positrons are moving quickly, allowing them to traverse significant distances before encountering electrons. The conversation references a bubble-chamber photograph that illustrates a positron track terminating due to a rare annihilation event with a stationary electron. This highlights the complexities of particle interactions and the conditions under which annihilation occurs.

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  • Understanding of particle physics concepts, particularly positron behavior.
  • Familiarity with Anderson cloud chambers and their detection mechanisms.
  • Knowledge of annihilation processes between positrons and electrons.
  • Basic grasp of bubble chamber experiments and their photographic evidence.
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  • Research the mechanics of positron-electron interactions in various environments.
  • Study the principles of Anderson cloud chambers and their historical significance in particle physics.
  • Explore the role of photon interactions in particle creation and annihilation.
  • Investigate the specifics of bubble chamber imaging and its applications in detecting particle tracks.
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Physicsislove30
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I was researching on the Anderson cloud chamber that discovered the positron in 1932. I couldn't help but wonder, if positron annihilates upon contact with an electron, how was it able to get till the cloud chamber without annihilation? Shouldn't the 2 photons be the only thing observed in the cloud chamber which are produced upon annihilation? Or does a cloud chamber detects only the existence of positron and does not mean that the positron is exactly at that point in that time.
 
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”Upon contact with an electron” is an extremely popularised version of what is going on. It is so inaccurate that no reasoning can be based on it.
 
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Orodruin said:
”Upon contact with an electron” is an extremely popularised version of what is going on. It is so inaccurate that no reasoning can be based on it.
Could you then tell me what the accurate reasoning is?
 
The probability of annihilation is very low unless the positron is moving slowly with respect to the electron. While it's slowing down its moving quickly and thus covers a lot of ground.
 
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The probability of annihilation is very low until it hits a heavy plate with a large density of electrons.
 
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