# Can mass be caused by massless particles in a bound state?

I read this question about mass being light moving in another dimension. I got a somewhat similar idea. Can't mass be generated by massless particles in a bound state? Which would mean that massless spin 1/2 particles find themselves in a bound state. They could form massive quarks and leptons. Of course the interaction has to be huge. But I see no fundamental difficulty. Massless spin 1/2 particles are described by Weyl spinors and gauge fields can be constructed. A kind of color force but much stronger.
All particles would move at the speed of light, and the masses of matter families explained. It could even be that there are equal amounts of matter and antimatter. Could it be?

I got a somewhat similar idea. Can't mass be generated by massless particles in a bound state? Which would mean that massless spin 1/2 particles find themselves in a bound state. They could form massive quarks and leptons. Of course the interaction has to be huge. But I see no fundamental difficulty.

Yes. Most of the mass of the proton and neutron (which means most of your mass) doesn't come from the mass of the quarks, but the binding energy of the quarks due to the strong force.

"Confinement" is the phenomenon by which we don't observe free quarks and gluons; the strong interactions mean that quarks and gluons always appear in bound states without a net color charge.

In fact, one of the Millennium Prize Problems is to show that Yang-Mills theory has a "mass gap." Perturbatively, Yang-Mills theory only has massless particles. But due to interactions between the gluons, massive bound states ("glueballs") form.

Massless spin 1/2 particles are described by Weyl spinors and gauge fields can be constructed. A kind of color force but much stronger.

There's no need to have a different force, the strong (color) force does exactly what you describe above.

All particles would move at the speed of light,

You have to be careful here -- free particles without mass travel at the speed of light, but the bound states with mass do not. Because of confinement, you don't expect to ever actually see free particles in QCD.

and the masses of matter families explained.

Confinement explains the mass of matter particles in the sense that you could compute the mass of the proton from first principles assuming you already know the mass of the quarks (see, eg, https://arxiv.org/abs/0906.3599). However it doesn't explain the masses of leptons and quarks due to the Higgs mechanism.

It could even be that there are equal amounts of matter and antimatter. Could it be?

This would contradict the observed matter-antimatter asymmetry in our Universe. But matter-antimatter asymmetry is a separate issue from confinement.

• +1: Just to emphasize what you already said, most of the mass of the matter we see doesn't come from the Higgs mechanism. :)
– user87745
Feb 13, 2022 at 1:29
• @DvijD.C. Indeed :) Feb 13, 2022 at 1:31
• @Felicia Your comment brings up two issues. First, while there is no experimental evidence of this to date, quarks and leptons could be made of more fundamental constituents. Indeed, the "technicolor" theory is very similar to what you are describing in your comment (but is difficult to make consistent with data from the LHC). The second issue is matter-antimatter asymmetry. This asymmetry is an observed fact about our Universe, so we need to explain the asymmetry, not symmetry. Feb 13, 2022 at 1:52
• @Felicia Sounds a bit like the Rishon model Feb 13, 2022 at 3:14
• @Felicia What you are describing -- the origin of all mass is binding energy -- is essentially the technicolor idea. It's a fine idea, but difficult to square with data from the LHC, which supports the Standard Model. In the Standard Model, some (actually, most) mass comes from binding energy, but some mass comes from the Higgs mechanism. A similar Higgs-ing could happen in the Rishon model. Neither technicolor nor the Higgs mechanism, however, explains the particular pattern of masses we observe. And neither model explains the matter-antimatter asymmetry. Feb 13, 2022 at 14:27