# Is Higgs mechanism necessary in QCD?

As we known, we introduce Higgs mechanism into Standard model to explain mass of Gauge boson, lepton and neutrino(maybe?). Higgs mechanism is necessary for electroweak theory because gauge symmetry and chiral symmetry.

But in QCD, Is Higgs mechanism still necessary? It seems there is no chiral symmetry in QCD so that mass of quark not necessarily to be zero. And on the other hand, gluon seems to be massless(maybe I am wrong?mass of proton). It seems like Higgs mechanism is not a necessary in QCD.

Is my understanding right? Thanks a lot!

• quarks are doublets - a mass is still forbidden by su2. You may have heard that hadron mass is mainly from as strong dynamics, which is correct. – innisfree Oct 18 '13 at 16:46
• @HuaWei Yes, gluons are massless. – user29727 Oct 18 '13 at 16:47
• @innisfree But is SU(2) necessary in QCD? Just like QED, we can have massive dirac field without Higgs mechanism. – Hua Wei Oct 18 '13 at 16:52
• Quarks interact with eg W boson. its necessary that quarks are in left-handed su2 doublets, which prohibits an explicit mass prior to symmetry breaking – innisfree Oct 18 '13 at 16:55
• (Left-Handed) Quarks obeys weak interaction too, and $Z_0, W^{\pm}$ are the gauge bosons of the weak interaction. – Trimok Oct 18 '13 at 17:00

If you completely forget all about $SU(2)_L$ (say, in an alternate universe with no Weak Interactions). Then mass terms in the Lagrangian for quarks and leptons are not forbidden by any symmetry and you would not need the Higgs field to generate the mass of the quarks or of the electron.