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22.10.2014 (Wednesday)

Non-perturbative elementary particle mass generation

Regular Seminar Giancarlo Rossi (INFN Rome)

at:
16:00 QMW
room G.O. Jones 610
abstract:

Taking inspiration from lattice QCD data, we argue that a finite non-perturbative mass contribution for quarks is generated as another consequence of the dynamical phenomenon of spontaneous chiral symmetry breaking, which is in turn triggered by the explicitly breaking of chiral symmetry induced by the critical Wilson term in the action. In pure lattice QCD this mass term cannot be separated from the unavoidably associated linearly divergent contribution. However, if QCD is enlarged to a theory where also a scalar field is present, coupled to a doublet of SU(2) fermions via a Yukawa and a Wilson-like term, then in the phase where the scalar field takes a non-vanishing expectation value, a dynamically generated and "naturally" light fermion mass (numerically unrelated to the expectation value of the scalar field) is conjectured to emerge at a critical value of the Yukawa coupling where the symmetry of the model is maximally enhanced. Masses dynamically generated in this way display a natural hierarchy according to which the stronger is the strongest of the interactions the fermion is subjected to the larger is its mass.