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PoS - Proceedings of Science
Volume 310 - XVII International Conference on Hadron Spectroscopy and Structure (Hadron2017) - Posters
SO(N) models and Higgs extensions
J.J. Sanz-Cillero*, A. González-Jerez and C. Quezada
Full text: pdf
Pre-published on: February 19, 2018
Published on: March 20, 2018
Abstract
We discuss previous studies on SO(N) linear sigma models (LσM) and some limits of phenomenological interest. These models suffer a spontaneous symmetry breaking (SSB) down to SO(N1), with the appearance of an associated vacuum expectation value (vev) f, a heavy scalar degree of freedom (dof) with mass M and N1 massless Nambu-Goldstone bosons (NGB). These models are of a high interest for beyond Standard Model extensions where the Higgs boson is identified with a pseudo Nambu-Goldstone boson (pNGB) that appears in the SO(N)/SO(N1) SSB. It gains a non-zero mass m due to soft explicit SO(N) symmetry breaking (ExSB) terms in the Lagrangian. In particular, we will focus on the soft breaking pattern SO(N)ExSBSO(4)×SO(P)SSBSO(3)×SO(P1), with 4+P=N, e.g., via new beyond Standard Model (BSM) gauge boson loops. The SO(4)/SO(3) are the electroweak (EW) chiral/custodial groups and the associated SSB is exactly the Standard Model (SM) one, giving mass to the W± and Z gauge bosons while avoiding large corrections to the oblique T parameter. The comparison of this type of models with the current phenomenological situation, close to the SM (m=0.125~TeV, EW vev v=0.246~TeV, M>O(TeV), ghWWgSMhWW) sets important constraints on the LσM parameters: there is a very small mixing between the heavy and light LσM massive scalars and the pNGB h is essentially SM-like, the low-energy effective field theory (EFT) couplings are very close to the SM ones, and a large hierarchy ξ=v2f21 is needed in these LσM near the SO(N) limit (and ξ much smaller than a certain ratio λ2λ1 of quartic LσM couplings in the general case). Likewise, we note the existence of strongly coupled scenarios with a hierarchy m2v2f2M2.
DOI: https://doi.org/10.22323/1.310.0251
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