Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Without the Higgs, would second & third generations of Fermions have the same mass as the first?

  1. Oct 20, 2016 #1
    if there were no higgs field, would the second and third generation of fermions, such as the top quark, be exactly the same mass as first generation?

    is the coupling between the top quark and the higgs field the sole reason the top quark is heaviest SM particle?

    is there a reason the top quark, and second and third generation fermions couple to the higgs field more strongly than the first generation?

    if there were no higgs field, would second and third generation fermions be stable and long-lived as first generation?
     
  2. jcsd
  3. Oct 21, 2016 #2

    arivero

    User Avatar
    Gold Member

    Could you elaborate about what alternative mass mechanism are you thinking about?
     
  4. Oct 21, 2016 #3
  5. Oct 21, 2016 #4
    why do third generation fermions interact more strongly with the higgs field than second, and second first. why does the top quark interact with the higgs field more strongly than an electron?
     
  6. Oct 21, 2016 #5

    Orodruin

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    The couplings of the Higgs field are free parameters in the Standard Model and directly related to the masses of the quarks. Therefore, a quark with a larger mass will interact more strongly with the Higgs field. In effect, it is the interaction with the Higgs field that provides the mass, implying that a quark that interacts more strongly with the Higgs field will have a larger mass.
     
  7. Oct 21, 2016 #6
    i understand it is a free parameter, but are there any physics explanations why second and third generation fermions interact more strongly with the higgs, such as a degree of freedom

    is there any reason why second and third generation fermions couldn't be lighter and couple less strongly than first generation to the higgs, since it is a free parameter and can take any value
     
  8. Oct 21, 2016 #7

    Orodruin

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    The lighter quarks are what we define as the first generation.
     
  9. Oct 21, 2016 #8
    since higgs coupling is a free parameter isn't it certainly conceivable that all 3 generations have the same coupling to the higgs and therefore same masses
     
  10. Oct 21, 2016 #9

    Orodruin

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    Yes, but this would be a rather strange situation where we would probably suspect that some symmetry was in play because there is no a priori reason for this to be the case.
     
  11. Oct 21, 2016 #10

    arivero

    User Avatar
    Gold Member

    In fact all the masses are almost zero compared to the top quark, so we could suspect a symmetry where all masses are null except the top quark, but this scenario is not asked/developed frequently, neither in literature nor even here in forums.

    EDIT: AFAIK, of course
     
    Last edited: Oct 21, 2016
  12. Oct 21, 2016 #11

    ohwilleke

    User Avatar
    Gold Member

    Given that the W bosons are the means by which quarks and charged leptons, at least, change from one flavor to another at frequencies that show a some crude relationship to the mass differences involved, surely the Higgs boson couplings and the CKM matrix that governs W boson quark flavor transformations, have some deeper connection to which we are not yet privy.

    Also, it isn't obvious that it is possible for particles to be distinct from each other in some means other than their propensity to change from one type to another (which would have no observable consequences if all other properties were the same) if they do not have some different properties, so it stands to reason that given that they are identical in everything else, that they ought to have different masses, and are assignment of those masses to particular generations in order of mass is something that can be done without loss of generality in every case where there are distinct masses.
     
  13. Oct 21, 2016 #12

    ohwilleke

    User Avatar
    Gold Member

    Not if the Higgs coupling is the source of masses in the universe. If all the couplings were the same the Higgs boson and field would be much simpler mathematically.
     
  14. Oct 21, 2016 #13
    Pauli exclusion principle effects should be observable: in the "Higgsless Universe", electrons and muons would look the same, but you'd notice that sometimes you can cram two of them into the same state, and sometimes you can't.
     
  15. Oct 21, 2016 #14

    arivero

    User Avatar
    Gold Member

    Hmm if all the three masses are equal, does the CKM matrix still has the same physical components? Or does some component become unphysical?
     
  16. Oct 21, 2016 #15

    Orodruin

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    The mixing in the quark sector is directly given by the mismatch between the left-handed transformations that diagonalise the up and down type Yukawa couplings.

    If all masses are equal the entire CKM matrix is unphysical. (In fact, it is sufficient that either the up or down type quarks have the same masses.)
     
  17. Oct 21, 2016 #16
    what would be a reason a priori they would be different? how can you tell apart a massless muon from a massless electron or tau
     
  18. Oct 21, 2016 #17
    in a higgless universe is it possible that there is NO difference between an electron tau or muon? they are all the same particle, the only difference is that sometimes the higgs is more strongly attracted to muon or tau, or that a muon or tau are quantized excited versions of electron
     
  19. Oct 21, 2016 #18

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    Not exactly. What would be observed is you can get 3 electrons into the same state. Eventually it would be explained as a hidden quantum number called "infracolor" or "ultracolor" or something like that, in analogy with QCD color.

    I wouldn't say "unphysical". "Trivial" and "unnecessary" seem to be more descriptive.
     
  20. Oct 21, 2016 #19

    arivero

    User Avatar
    Gold Member

    It is not gauge, so flavor is still a good name.
    My vote is with "Trivial".

    Is it right to think that while we need three different masses to have a full non trivial CKM matrix, we do not need six?
     
  21. Oct 21, 2016 #20

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    I am not sure that people would immediately conclude that. I suspect they would start putting together "ultraweak" theories to try and explain flavor. We sort of do this today with topcolor-style theories.

    Has to be the right three. All the +2/3 or all the -1/3. That allows you to change the basis so the CKM matrix is the identity. If you make e.g. two of the +2/3's degenerate with one of the -1/3's, you still have a nontrivial matrix. However, that matrix will be real, so there will be no CP violation.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Without the Higgs, would second & third generations of Fermions have the same mass as the first?
  1. Fermions mass terms (Replies: 5)

Loading...