Why CP symmetry is violated in weak interaction?

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Discussion Overview

The discussion centers on the violation of CP symmetry in weak interactions, exploring theoretical explanations and empirical observations. Participants examine the implications of neutrino mass and the structure of the Standard Model (SM) in relation to CP violation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether CP symmetry violation in electro-weak interactions is related to the mass of neutrinos being zero, suggesting that this prevents mixing between left and right neutrinos.
  • Another participant corrects the first claim, stating that the mass of neutrinos is not zero and emphasizes that the reason for CP violation is still unknown, describing it as a property of the universe.
  • A participant suggests rephrasing "why" questions to avoid philosophical implications, proposing a focus on the mechanisms of CP violation in weak interactions instead.
  • It is noted that the left-right asymmetry cannot be derived from weak interaction theory alone, and that CP violation is an empirical result rather than a derived one.
  • Participants mention that while mathematical models exist to describe CP violation, they do not accurately predict the magnitudes observed in experiments.
  • One participant expresses concern about potentially confusing explanations regarding the relationship between CP symmetry and the strong interaction.
  • Another participant states that constructing the SM model Lagrangian requires explicit breaking of chiral symmetry, indicating that a chiral symmetric theory could also be mathematically valid.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between neutrino mass and CP violation, with some asserting that the reasons for CP violation remain unresolved. There is no consensus on the mechanisms or models that adequately explain the observed phenomena.

Contextual Notes

Participants acknowledge limitations in current models and the need for further exploration of the underlying physics. The discussion reflects ongoing uncertainty in the field regarding CP violation and its implications.

ndung200790
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Please teach me this:
Why is CP symmetry violated in electro-weak interaction? Is it correct that because of the mass of neutrino is zero(so that the left and righ neutrinos do not mix with each other)?
Thank you very much in advance.
 
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ndung200790 said:
Please teach me this:
Why is CP symmetry violated in electro-weak interaction? Is it correct that because of the mass of neutrino is zero(so that the left and righ neutrinos do not mix with each other)?
Thank you very much in advance.
Mass of neutrino is not zero - you seem to be using an old source.

IFAIK: the correct answer to your question is "we don't know".
It seems to be a property of the Universe.

We also have to be careful with "why" questions. Try rewording as a "how" or "what" or something - we leave "why" to philosophers. Thus I have interpreted your question as "what is it about the electroweak interaction that leads to CP violations?"
 
So,from weak interaction theory(meaning massive boson gauge theory) we can not derive the left-righ asymmetry?
 
It is an empirical result, that is my understanding - yes.

We can describe it in the math, and several models for underlying behavior have been proposed which give CP violations ... however, the models don't give anything like the correct magnitudes.

You'll see from the gauge theory that the CP violation it is pretty much plugged in. There are some clues in the way the strong interaction is CP-symmetric. You'll meet the different ideas as you progress. I'm worried that if I try to describe them here, I'll just confuse you more or inadvertently mislead you.

It is possible that things have advanced a bit since I last looked, but a quick trawl suggests "not substantially". I'll leave it to the others to contradict me :)

Welcome to the edge of known physics.
Exciting isn't it?

You should probably find a theoretical physicist in your college working on this.
 
ndung200790 said:
So,from weak interaction theory(meaning massive boson gauge theory) we can not derive the left-righ asymmetry?

No, we can't.

Constructing the SM model Lagrangian with it's U(1)*SU(2) structure in the el.-weak sector and adding the Higgs boson nobody else but nature tells you that you have to have to break chiral symmetry explicitly in the Lagrangian. The mathematical construction itself would work with a chiral symmetric theory as well.
 

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