Spin of Particle and Antiparticle: Same or Different?

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Discussion Overview

The discussion centers around whether the spin of a particle and its antiparticle is always the same, exploring the implications of quantum mechanics and charge conjugation. Participants examine theoretical aspects and clarify concepts related to spin in the context of particle-antiparticle relationships.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant asks if the antiparticle always has the same spin as the particle and under what conditions this might differ.
  • Another participant asserts that the charge conjugation operator commutes with the spin operators, suggesting that the antiparticle always has the same spin as the particle.
  • A further contribution agrees with the previous point but adds that the spins must be the same for Lorentz invariance in the presence of conserved charges.
  • A participant seeking clarification questions whether changing the spin of one particle would affect the other, indicating a lack of understanding of the concept.
  • Another participant clarifies that "the spin" refers to a general property that cannot be changed, while the orientation of the spin can vary independently for each particle.

Areas of Agreement / Disagreement

There is a general agreement among some participants that the antiparticle has the same spin as the particle due to theoretical principles. However, there is a lack of consensus on the implications of this relationship, particularly regarding the ability to change spin and the independence of spin orientation.

Contextual Notes

Participants express varying levels of understanding of the concepts involved, with some relying on theoretical assertions while others seek clarification on the implications of spin properties.

Who May Find This Useful

This discussion may be useful for students and individuals interested in quantum mechanics, particle physics, and the properties of particles and antiparticles.

stjimmee
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So a simple question, really: Given a particle, will its antiparticle always have the same spin or not? And if not, in which cases will the spin be different?
Thanks in advance.
 
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Yes, the charge conjugation operator commutes with the spin operators, so the antiparticle always has the same spin as the particle.
 
fzero said:
Yes, the charge conjugation operator commutes with the spin operators, so the antiparticle always has the same spin as the particle.

This is not the real reason why the spins are the same. The spin, or any other quantum numbers of the antiparticle has to be the same with that of the particle, in order for them to be able to establish Lorentz invariance in the presence of conserved charges.
 
Clarification

I'm not really that far in physics (more of an applied guy--and a high school junior), so maybe this question is obvious. Does that mean that if I were to change the spin of one particle, the other would change as well?
 
No. "The spin" in the first 3 posts refers to the general property of the particle, similar to "the electric charge" or "the mass". You cannot change those (at least not in current physics).

The actual orientation of this spin can change, and it can change for each particle individually. There is no single "other particle".
 

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