Conservation of Total Spin in the Stern Gerlach Experiment

Click For Summary

Discussion Overview

The discussion revolves around the conservation of total spin in the context of the Stern-Gerlach experiment, particularly focusing on the behavior of electron-positron pairs and their spin states after annihilation and subsequent pair production from photons. The scope includes theoretical considerations and conceptual clarifications related to quantum mechanics.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant poses a hypothetical scenario involving the passage of an electron and positron through separate Stern-Gerlach apparatuses and questions whether the spin states can be determined after annihilation and pair production.
  • Another participant asserts that while total spin is conserved in the described sequence of operations, individual spins of the particles are not conserved.
  • A follow-up question is raised regarding the correlation between photon polarization and the spin of the electron-positron pair during pair production.
  • It is clarified that there is no known correlation for the individual spins of the particles, emphasizing that only the total spin is conserved.

Areas of Agreement / Disagreement

Participants generally agree that total spin is conserved, but there is no consensus on the implications for individual spins, indicating a contested understanding of the relationship between photon polarization and particle spin.

Contextual Notes

The discussion does not resolve the complexities surrounding the relationship between photon polarization and the spin states of produced particles, leaving open questions regarding the assumptions involved in the scenario presented.

CassiopeiaA
Messages
31
Reaction score
0
I just started reading Stern Gerlach Experiment and this thought crossed my mind. Totally a hypothetical question. If I pass an electron and positron through separate SG apparatuses, I will know in which spin state each particle has collapsed. But afterwords I let electron-positron pair annihilate to produce 2 photons. I let these photon Interact with each other and again produce an electron-positron pair. So, if I again check the spin state of these particles separately, in the same direction as before, will I get the same result or is it again completely random?

P.S. I am just a school student trying to learn something difficult for me to understand. So please spare my ignorance.
 
Physics news on Phys.org
CassiopeiaA said:
if I again check the spin state of these particles separately, in the same direction as before, will I get the same result

No. The sequence of operations you describe will conserve the total spin, but it will not conserve the individual spins of the particles.
 
PeterDonis said:
No. The sequence of operations you describe will conserve the total spin, but it will not conserve the individual spins of the particles.
Oh Okay. So there is no known correlation between photon polarization and spin of electron-positron pair in case of pair production?
 
CassiopeiaA said:
So there is no known correlation between photon polarization and spin of electron-positron pair in case of pair production?

Not for the individual particles. As I said, only the total spin is conserved.
 
PeterDonis said:
Not for the individual particles. As I said, only the total spin is conserved.

Okay thanks.
 

Similar threads

Undergrad Is Calcite a parallel to the Stern-Gerlach experiment?
  • · Replies 43 ·
2
Replies
43
Views
4K
Graduate Quantitative description of successive Stern-Gerlach measurements
  • · Replies 1 ·
Replies
1
Views
2K
Undergrad How many spots will a rotating Stern-Gerlach apparatus produce?
  • · Replies 32 ·
2
Replies
32
Views
2K
Undergrad Question about Stern-Gerlach experiment
  • · Replies 12 ·
Replies
12
Views
3K
Undergrad Problem involving a sequential Stern-Gerlach experiment
  • · Replies 24 ·
Replies
24
Views
4K
High School Double slit experiment combined with Stern-Gerlach
  • · Replies 1 ·
Replies
1
Views
2K
Graduate Another thought experiment about spin 1/2
  • · Replies 15 ·
Replies
15
Views
2K
Undergrad Who was the first to make a Stern-Gerlach experiment with two magnets?
  • · Replies 9 ·
Replies
9
Views
2K
Undergrad Measuring electron spin and measuring entangled electron spin
  • · Replies 12 ·
Replies
12
Views
2K
High School Spin collapse in a magnetic field
  • · Replies 17 ·
Replies
17
Views
2K