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

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Discussion Overview

The discussion centers on the stability of the top quark and other fermions in a hypothetical universe without the Higgs field. Participants explore the implications of massless fermions, the role of Yukawa couplings, and how these concepts relate to distinguishing between different generations of particles.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants propose that in a universe without the Higgs field, fermions would be massless and question the stability of second and third generation fermions like the top quark.
  • Others argue that without Yukawa couplings, it would be impossible to distinguish between massless particles such as electrons, muons, and taus.
  • A participant suggests that if Yukawa couplings are the means by which particles are distinguished in a Higgs universe, then their absence in a Higgs-less universe raises questions about how massless particles could acquire distinguishable properties.
  • There is a discussion about whether multiple Higgs fields could lead to different Yukawa couplings and thus different masses for fermions, with some participants questioning the implications of such models.
  • Some participants assert that while you could identify the existence of three generations of fermions in a Higgs-less universe, you could not distinguish between them.
  • Questions arise regarding the nature of cross sections in scattering processes involving massless particles and whether they would differ based on the number of generations present.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the implications of a Higgs-less universe, particularly concerning the stability and distinguishability of fermions. There is no consensus on how these concepts interact or the outcomes of such a theoretical scenario.

Contextual Notes

Limitations include the dependence on the definitions of mass and stability in the absence of the Higgs field, as well as unresolved questions about the nature of Yukawa couplings and their role in particle interactions.

  • #31
Orodruin said:
Yes, but you would likely have to give a very good argument as to why these fields would not couple to all fermions as allowed by the quantum numbers.

are there any proposals to extend the SM with additional degree of freedom and quantum numbers, to allow for a "higgs charge" so that second and third generation fermions have more higgs-charge than first generation via yukawa coupling?
 
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  • #32
kodama said:
are there any proposals to extend the SM with additional degree of freedom and quantum numbers, to allow for a "higgs charge" so that second and third generation fermions have more higgs-charge than first generation via yukawa coupling?
What do you think the Yukawa couplings are? They describe how strongly the different fermions couple to the Higgs field.

Edit: Note that they are not a charge in the sense of a charge related to a gauge symmetry.
 
  • #33
Orodruin said:
What do you think the Yukawa couplings are? They describe how strongly the different fermions couple to the Higgs field.

Edit: Note that they are not a charge in the sense of a charge related to a gauge symmetry.

that's what i am wondering about

a hypothesis that the reason second and third generation fermions are heavier than first and interact more strongly with the higgs field there is a higgs-charge that is a charge in the sense of a charge related to a gauge symmetry
 
  • #34
The coupling constants are these charges you are looking for. It doesn't matter if you call them coupling constants or charges. Same thing.
Orodruin said:
If there is no Higgs the Z is massless and does not decay (well, truth with modification). This is why I said cross sections instead of decays. A closer analogue would be the QCD color factors.
There would also be no physicists to perform experiments ;).
 
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  • #35
mfb said:
The coupling constants are these charges you are looking for. It doesn't matter if you call them coupling constants or charges. Same thing.There would also be no physicists to perform experiments ;).

isn't that another degree of freedom that all fermions and w and z bosons posses? a higgs-charge that determine yukawa interaction.

in a higgless universe, all particles then would be massless and travel at the speed of c is that correct? but they still have their charges so they could form something
 
  • #36
kodama said:
that's what i am wondering about

a hypothesis that the reason second and third generation fermions are heavier than first and interact more strongly with the higgs field there is a higgs-charge that is a charge in the sense of a charge related to a gauge symmetry

Yukava couplings are partially analogous to charges. The difference is that charges related to a gauge symmetry manifest themselves as a constant in the gauge covariant derivative's formula, and this constant is the same for all particles. For QED, the constant is the electron's charge.

Yukava couplings are constants too, but they are _different_ for every higgs-to-fermion coupling. No evidence so far exists that they are multiples of some fundamental, minimal "charge".

The reason for this difference is that coupling terms in Lagrangian for fermion-to-spin1-boson coupling and fermion-to-spin0-boson coupling have different forms.
 
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  • #37
Orodruin said:
If there is no Higgs the Z is massless and does not decay (well, truth with modification).
I don't get that part, why wouldn't Z decay?
 
  • #38
ChrisVer said:
I don't get that part, why wouldn't Z decay?
How many massless particles do you know that decay?
 
  • #39
Orodruin said:
How many massless particles do you know that decay?
I know 1 massless particle out of the 1 massless particles there which can decay (well not alone)...
 
  • #40
ChrisVer said:
(well not alone)...
So, not a decay.
 
  • #41
This means that in a Higgsless universe you would not have 3 neutrino flavors also?
 
  • #42
You would still have three flavors. If you can distinguish between different neutrino types depends on the mechanism that leads to neutrino masses, but the different masses (if applicable) would be the only difference you could see.
 
  • #43
mfb said:
You would still have three flavors. If you can distinguish between different neutrino types depends on the mechanism that leads to neutrino masses, but the different masses (if applicable) would be the only difference you could see.
Many (not all, but I would say a majority of) neutrino mass models give rise to neutrino masses through the appearance of a Weinberg operator after integrating out some heavy states. Without the Higgs, such operators do not exist.
 
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  • #44
in a higgless universe, what would happen if a tau interacts with a positron?
 
  • #45
kodama said:
in a higgless universe, what would happen if a tau interacts with a positron?
What happens in this universe (Higgsfull) when a tau interacts with a positron?
I don't know, is the Lepton number also associated with the existence of the Higgs?
 
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  • #46
ChrisVer said:
What happens in this universe (Higgsfull) when a tau interacts with a positron?
I don't know, is the Lepton number also associated with the existence of the Higgs?

i was going to ask that to
 
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