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Directions Beyond the Standard Model

The Hierarchy Problem and possible solutions:

Since it is a scalar particle, the mass o the Higgs boson Mh ~ MEW is not protected by any symmetry and thus generically receives corrections from all scales present in nature, which could be the scale of grand unification, MGUT ~ 1015 GeV or the Planck scale MPL ~ 1019 GeV. Building models that stabilize MEW << MPL remains a major branch of particle physics research.

Two well known solutions to the hierarchy problems are supersymmetry, SUSY, under which the Higgs boson transforms into a fermion and thus allows for a protection of its mass, and composite Higgs (CH) models, where Mh is cut off at the compositeness scale, above which the Higgs is no point-like particle anymore (moreover, the Higgs is realized as a Goldstone mode). Such models also allow to solve other issues, like the unification of coupling constants, the dark matter problem, or flavor hierarchies, however start to be in tension with null results from the LHC in searches for predicted partner particles of SM states.

One focus of NEWFO is to propose and explore new realizations of the fermion sector of CH models to address this tension, such as in the model of lepton flavor that was presented in [1], which naturally raises the fermionic partners above currently tested scales (see figure above) and, generally, to propose new approaches to the hierarchy problem. Another field of investigation is models that solve simultaneously other issues of the SM, like the strong CP, flavor, and dark matter puzzles, as the axion model of [2]. Beyond that, ‘model independent’ effective field theory approaches are followed to close in on the completion of the SM (see SMEFT).

[1] A. Carmona, F. Goertz, JHEP 1505 (2015) 002
[2] L. Calibbi, F. Goertz, D. Redigolo, R. Ziegler, J. Zupan, 1612.08040