mollwollfumble said:
Tau.Neutrino said:
The Strength of the Strong Force – Accounting for 99% of the Ordinary Mass in the Universe
Thomas Jefferson National Laboratory experiments hone in on a never-before-measured region of strong force coupling, a quantity that supports theories accounting for 99% of the ordinary mass in the universe.
Much fanfare was made about the Higgs boson when this elusive particle was discovered in 2012. Although it was touted as giving ordinary matter mass, interactions with the Higgs field only generate about 1% of ordinary mass. The other 99% comes from phenomena associated with the strong nuclear force, the fundamental force that binds smaller particles called quarks into larger particles called protons and neutrons that comprise the nucleus of the atoms of ordinary matter.
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> Although it was touted as giving ordinary matter mass, interactions with the Higgs field only generate about 1% of ordinary mass. The other 99% comes from phenomena associated with the strong nuclear force.
I knew that the strong force made a major contribution to particle rest masses, but I hadn’t realised that that the percentage was that high.
This needs checking.
Up quark mass 2.0 MeV
Down quark mass 4.8 MeV
Proton mass 938 MeV
Neutron mass 940 MeV
A proton is 2 ups and a down, so the Higgs gives it a mass of 8.8 MeV
A neutron is 2 downs and an up, so the Higgs gives it a mass of 11.6 Mev
The strong force accounts for the rest,
which is (939-8.8)/938 = 99.2% of a proton’s mass
and (940-11.6)/940 = 98.8% of a neutron’s mass
So on Earth, with roughly equal numbers of protons an neutrons, it averages out to about 99%.
Which is just what they said.
> This is because the quarks gather a cloud of gluons, the particle that carries the strong force, as they move across larger distances. The mass-generating effect of this cloud accounts for most of the mass in the universe – without this additional mass, the textbook mass of quarks can only account for about 1% of the mass of protons and neutrons. The other 99% comes from this acquired mass.
I should have realised that. But it also makes sense to say that protons and neutrons gather clouds of mesons – quark-antiquark pairs – which is how I think of it. Yukawa coupling.
> “If gluons remained massless at long range, strong force coupling would keep growing unchecked,” Deur said. “Our measurements show that strong force coupling becomes constant as the distance probed gets larger, which is a sign that gluons have acquired mass through the same mechanism that gives 99% of mass to the proton and the neutron.”
That’s new! I had heard that the strong force coupling grows unchecked at long range. So I was wrong there.
> These results also help verify new ways to solve equations for quantum chromodynamics (QCD)
Yes. It would.
> the flattening of the strong force coupling at large distances provides evidence that physicists can apply a new, cutting-edge technique called Anti-de Sitter/Conformal Field Theory (AdS/CFT) duality. The AdS/CFT technique allows physicists to solve equations non-iteratively, which can help with strong force calculations at large distances where iterative methods fail.
Oh, nice.
I know the iterative methods and was aware that they did fail.