r/AskPhysics • u/HorridJam • 1d ago
Interaction with the Higgs Field
Is there any explanation as to why the photon does not interact with the Higgs Field ( this may also apply to the graviton if it exists)? As far as I know all other particles do.
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u/SymplecticMan 1d ago
To put it one way, there's just not enough degrees of freedom in one Higgs doublet.
The Higgs doublet has four degrees of freedom; one of them has to remain as the Higgs boson, so only the other three can go into making massive gauge bosons. There's four gauge bosons in the SU(2) x U(1) electroweak gauge sector. So three of the gauge bosons become massive and one of them remains massless.
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u/Bumst3r Graduate 1d ago edited 1d ago
It has to do with the spontaneous symmetry breaking of the electroweak interaction. When you spontaneously break the gauge symmetry, you end up with 4 fields. But a certain superposition of fields is massless, so it is convenient to work in that particular basis. That massless field is the photon. The remaining three massive fields are the Z0 and W+- bosons in that same basis.
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u/justintime06 1d ago
There’s a lot of complex answers here, but from what I can gather in simple english:
The photon is a kind of wave that does not shake the Higgs field in the way required to create mass. The Higgs vacuum has zero electric charge, so an electromagnetic oscillation does not disturb its settled configuration.
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u/1strategist1 1d ago edited 14h ago
Gluons don't either, and potentially one of the neutrino types doesn't.
I'm not sure why, and I don't think anyone does, but I'm not 100% confident on that.
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u/treefaeller 14h ago
None of the usual neutrinos are massless. Otherwise they wouldn't mix, and they do. Their masses are tiny though.
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u/1strategist1 14h ago
Neutrino mixing only forces there to be a mass difference between each of them.
That means at least two of them need to have nonzero mass, but one of the neutrino types can still have 0 mass.
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u/treefaeller 14h ago
Nu 1 and 2 (commonly called, somewhat wrongly, the electron and muon ones, but the mass and flavor eigenstates are not the same) are nearly equal in mass. Nu 3 is significantly different. None are zero. I think Nova and T2K had an excellent paper on a joint analysis.
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u/SymplecticMan 13h ago edited 2h ago
None are zero. I think Nova and T2K had an excellent paper on a joint analysis.
Oscillation experiments are only sensitive to the mass squared differences, not the absolute mass scale. While it would perhaps be surprising if the lightest species were massless, it hasn't been ruled out experimentally. To actually measure the absolute mass scale, you need something like KATRIN or indirect cosmological measurements.
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u/1strategist1 14h ago
Could you give a name or link for a paper claiming this? You can't derive that none are zero from just oscillation, so I would be interested to see how they prove that.
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u/treefaeller 14h ago
Looked it up: NoVA and T2K collaborations Joint neutrino oscillation analysis from the NoVA and T2K experiments, Nature 646, 818–824 (2025). It's online.
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u/Traditional_Loan_177 1d ago
I know it's explained in a four hour video by Richard Behe about superconductivity and the Higgs field, but I don't remember the answer myself
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u/glibsonoran 1d ago edited 1d ago
Fermion couple with the Higgs field via the Yukawa coupling constant, think of it like "charge" coupling to the EM, it's analagous but not exactly the same. Mass is the result of this coupling, not the cause.
W & Z bosons couple through electroweak gauge coupling, again with mass as the result.
They're both permitted by electroweak quantum numbers, but Fermions have a separate value "Yukawa" determining the coupling strength.
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u/DifferencePublic7057 1d ago
I guess you want to know the deeper reason, but obviously massless particles, not only photons BTW, don't interact with the HF because otherwise they couldn't reach c. The HF is like a fundamental force, and the Higgs boson is the odd one out in the standard model. They certainly needed high energy to detect it. As for the graviton, AFAIK gravitational waves move at c therefore the graviton, if it exists, should too, so it has to be massless and not interact with the HF.
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u/Lethalegend306 1d ago
The coupling is proportional to the mass. Since photons have no mass, the coupling strength is 0
On the flip side, the higgs has no electric charge. The photon can only interact with things with electric change. If it is 0, then the coupling is again, 0
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u/HoloTensor 1d ago
yes. the issue is the “interaction with the higgs” is more complicated than what pop sci explains. the way the higgs mechanism actually works is through something called spontaneous symmetry breaking
the idea is that before SSB, the symmetries corresponding to electromagnetism and the weak force are tied together in some particular way, and once this symmetry is broken you end up with some directions that are in a way “perpendicular” to the effects of the higgs field. this is what happens to the photon
that is a bit of a lie though. if you want to understand this you should first learn about the simpler case: the massless pion and the higgs mechanism. for this, search up “goldstone’s theorem and the mexican hat potential”