What particles have fixed weak isospin and T3?

[Gene Naden]

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?

 

[Gene Naden]

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?

 

[ChrisVer]

the mass terms

 

[ChrisVer]

what particles you mean?
In general it's not an observable because the electroweak symmetry is broken.

 

[berkeman]

(Note -- two similar threads merged)

 

[Gene Naden]

Still wondering what is the reaction

 

[Gene Naden]

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.