What particles have fixed weak isospin and T3?

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Discussion Overview

The discussion revolves around the concept of weak isospin and its applicability to various particles, particularly focusing on why some particles have defined weak isospin values while others, like pions, do not. Participants explore the implications of weak isospin in the context of particle interactions and the effects of the Higgs field.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Some participants question why weak isospin values are provided for certain particles, such as left-handed electrons, while others, like pions, lack such values.
  • There is a suggestion that weak isospin may not be an observable quantity for all particles, particularly due to the breaking of electroweak symmetry.
  • One participant inquires about specific examples of particle reactions where weak isospin is not conserved, particularly in relation to interactions with the Higgs field.
  • Another participant notes the importance of mass terms in the context of weak isospin, although the details remain unclear.
  • There is a call for clarification on the conditions under which particles possess definite values for weak isospin (T) and its third component (T3).

Areas of Agreement / Disagreement

Participants express uncertainty regarding the conditions that determine weak isospin values for different particles, indicating that multiple competing views remain on the topic.

Contextual Notes

The discussion highlights limitations in understanding weak isospin, particularly concerning the definitions and implications of mass terms and electroweak symmetry breaking.

Who May Find This Useful

Readers interested in particle physics, particularly those exploring the electroweak interaction and the role of the Higgs field in particle properties.

Gene Naden
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Wikipedia quotes weak isospin values for some particles and not for others. Why? Is the concept of weak isospin as an observable quantity not meaningful for, for example, pions?
 
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Wikipedia article on weak isospin seems to say that in some cases it is not conserved due to interaction with the Higgs field. What would be an example of a particle reaction where this is true?
 
the mass terms
 
what particles you mean?
In general it's not an observable because the electroweak symmetry is broken.
 
(Note -- two similar threads merged)
 
Still wondering what is the reaction
 
Wikipedia gives a value for the weak isospin of left-handed electrons, even though they have mass. But not for pions. So when does a particle have a definite value for T and T3 and when does it not. Thanks.
 

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