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I Is the top quark stable in the absence of the Higgs field?

  1. May 10, 2017 #1
    in a universe without the higgs field

    fermions would be massless

    in absence of the higgs field, would second and third generation fermions such as muon tau top quarks etc be stable?

    how to distinguish between a massless electron muon and a tau in a universe without the higgs field, same for neutrinos and quarks of different generation
     
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  3. May 10, 2017 #2

    Orodruin

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    You cannot distinguish them - or linear combinations of them - without Yukawa couplings.
     
  4. May 10, 2017 #3
    why does the Yukawa couplings for a tau or muon differ for that of an electron if You cannot distinguish them in a higgless universe?
     
  5. May 10, 2017 #4

    mfb

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    Why do the Yukawa couplings for a tau or muon differ for the electron coupling if there is no Yukawa coupling? Is that your question?
     
  6. May 10, 2017 #5
    no my question is that in a higgless universe, there is no way to distinguish massless electron muon and a tau.

    how does the presence of the higgs field distinguish electron muon and a tau?

    if the answer is via via Yukawa couplings

    then how, in a higgless universe there is no way to distinguish massless electron muon and a tau acquire Yukawa couplings that distinguish them in a higgs universe
     
  7. May 10, 2017 #6

    mfb

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    It is.

    In our universe the particles have different Yukawa couplings, that makes them distinguishable.

    In a universe without Higgs (or similar) the particles behave exactly identical, there is nothing that would distinguish them.
     
  8. May 10, 2017 #7
    well ok,

    but imagine these 2 scenarios

    in one universe, particles have different Yukawa couplings, that makes them distinguishable electrons muons tau

    in another universe, only first generation fermions are truly fundamental, such as an electron, but certain quantum processes occur that can change their Yukawa couplings, that makes them distinguishable and the excited first generation fermions are called muons and tau.
     
  9. May 10, 2017 #8

    Orodruin

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    The Yukawa couplings are the couplings of fermions to the Higgs field. In a higgsless universe there are no Yukawa couplings.
     
  10. May 10, 2017 #9

    mfb

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    Do you have a reference discussing such a model?
    What does "processes that can change a coupling" mean?
     
  11. May 10, 2017 #10
    let me put it this way,

    in a higgless universe where electrons exist, would muons and tau particles also exist as fundamental particles?
     
    Last edited: May 10, 2017
  12. May 10, 2017 #11
    MSSM and SUSY and GUT models famously predict multiple higgs fields.

    if there is more than 1 higgs field, and other higgs fields Yukawa couplings couples to fermions larger than the SM 126 gev higgs, wouldn't those fermions have higher masses?
     
  13. May 10, 2017 #12

    Orodruin

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    This depends on the field content of that universe. If you just removed the Higgs field from the SM, yes - you could tell that there were three generations. You could not tell the generations apart.

    The fermion masses depend on the vevs and couplings, not on the Higgs masses.
     
  14. May 10, 2017 #13
    if you remove the Higgs field from the SM how "you could tell that there were three generations. You could not tell the generations apart" at the same time?
     
  15. May 10, 2017 #14
    in a universe or theory where there is a second and third higgs field with different vevs and couplings that couple to fermions differently from the first SM higgs field, wouldn't that in effect create a second and third generation?
     
  16. May 10, 2017 #15

    Orodruin

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    By looking at the cross sections of different scattering processes.

    No. It is sufficient with one higgs field for that.
     
  17. May 10, 2017 #16
    how would the cross sections of different scattering processes of a massless muon differ from a massless tau in absence of the higgs field?
     
  18. May 10, 2017 #17

    Orodruin

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    It wouldn't and I never said it would.
     
  19. May 10, 2017 #18
    to clarify i was responding to your earlier claim

    so i replied to you by saying how "can you tell there were three generations" and "You could not tell the generations apart."

    which you replied by cross sections of different scattering processes.

    but i had in mind we are still talking about SM in a higgless universe.
     
  20. May 10, 2017 #19

    Orodruin

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    You are misreading my statements. I never said the different generations would have different cross sections. I said cross sections would be different depending on the number of generations.
     
  21. May 10, 2017 #20
    ok, "cross sections would be different depending on the number of generations" is this true in a higgless universe?

    in a higgless universe where electrons muons and tau are all massless, is it still true "cross sections would be different depending on the number of generations"

    in a higgless universe what would cross sections would be different depending on the number of generations if the generations is 1, 2, 3 or 4 or higher?
     
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