HIP NEWS October 12th 2015
DEPARTMENT OF PHYSICS / HIP JOINT COLLOQUIA / SEMINARS
Tuesday 13 October 2015 at 10.15 in A315
Alejandro Cabo (La Habana, Cuba)
Is a generalized NJL model the effective action of massless QCD?
Abstract: A local and gauge invariant alternative version of QCD for massive fermions introduced in previous works, is considered here to
propose a model which includes Nambu-Jona-Lasinio (NJL) terms in the action. The Lagrangian includes new vertices which at first sight look as breaking power counting renormalizability. However, these terms also modify the quark propagators, to become more convergent at large momenta, thus indicating that the theory is renormalizable. Therefore, it follows the surprising conclusion that the added NJL four fermion terms do not break renormalizability. The approach can also be interpreted as a slightly generalized renormalization procedure for massless QCD, which seems able to incorporate the mass generating properties for the quarks of the NJL model, in a renormalizable way. It also seems to have opportunity to implement Fritzsch’s Democratic Symmetry description of the quark mass hierarchy.
Thursday 15 October 2015 at 10.15 in A315
Tommi Alanne (CP3-Origins, Odense)
Elementary Goldstone Higgs and raising the fundamental scale
Abstract: We study an extension of the scalar sector of the Standard Model (SM) where the observed Higgs is a pseudo-Goldstone boson (pGB) associated with the global symmetry breaking pattern SU(4) to Sp(4). This particular breaking pattern is interesting, because depending on the embedding of the electroweak (EW) symmetry, the breaking of the global symmetry can either leave the full EW sector intact, break the EW completely to electromagnetism, or more interestingly lead to something between these two extreme cases. In the unbroken case, the entire Higgs doublet can be identified with four of the five Goldstone bosons of the global symmetry breaking.
All of the different alignments of the EW symmetry are equivalent at the tree-level, but since the gauging of the electroweak sector and introducing Yukawa terms for the SM fermions break the global symmetry of the scalar sector, quantum effects determine a preferred vacuum alignment.
In this talk, I will present the main results of our study and show that very slightly broken EW symmetry is preferred. Therefore, the observed Higgs boson is dominantly a pGB, and interestingly the electroweak scale emerges due to the alignment of the EW sector in the global symmetry, whereas the fundamental scale of the spontaneous symmetry breaking is significantly higher.
A. Cabo 2.10. – 27.10. (AT)