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I am trying to understand mass. The Standard model contains an electroweak field where mass of everything comes from the Higgs field. The Standard model also contains Quantum Chromodynamics with a different reason for mass. Isn't this contradictory, since they are both part of the standard model?

Ruslan
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user78939
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I am trying to understand mass. The Standard model contains an electroweak field where mass of everything comes from the Higg's field. The Standard model also contains Quantum Chromodynamics with a different reason for mass. Isn't this contradictory, since they are both part of the standard model?

Basically, the Higgs "gives mass" to the known massive particles, although the masses are not determined by the Higgs alone (but are proportional to the Higgs vacuum expectation value).

For example, the W and Z bosons become massive when the Higgs breaks electroweak symmetry, whereas the photon remains massless. The Higgs Mechanics generates mass terms for the elementary fermions, e.g., electrons, as well. However, there are other contributions to the mass of composite particles like protons and so on.

For example, the mass of the "three" quark constituents of a proton doesn't add up to the mass of a proton, but that difference in mass is a little hard to explain in simple terms because QCD is asymptotically free, which basically means that QCD is hard to understand at low energies. You can basically say the mass difference can be accounted for by interactions and the interactions are mediated by gluons.

Anyways, there's no contradiction.

hft
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the bare mass of every fermion in the standard model comes from the higgs field.

the bare mass of quarks too comes as such and it is something like 4 -8 MeV for the u and d quarks as contributed by higgs mechanism.

but inside a stable hadron, lets say proton, the quarks get a constituent mass due to low energy QCD which has a very high coupling constant and it enhances the constituent quark mass to about 330 MeV. That's due to the fact that in the stable low energy ground state, there is a virtual sea of gluons and quark-antiquark pairs attached to it which gives it a high mass. the reason for only QCD contributions as such in contrast to QED contributions is due to its very high coupling constant in the low energy limit (of order of ground state energy) in contrast to to the QED coupling constant which remains low.

also there are gluon gluon interactions too in QCD which don't let the gluons get very far from each quark agglomerate and as a result contribute to the mass of the agglomerate by sticking to it. this speciality is introduced to to the SU(3) gauge group structure of QCD.

Bruce Lee
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When electroweak symmetry broken spontenously, Nambu-Goldstone bosons become massive, which refer to 3 gauge boson W,Z.

QCD is a different process. Quarks can not stay 'isolated'. They should form any bound state (which refers to hadrons) with gluonic interactions. These strong interactions give mass to hadrons additionally.

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