Abstract
We present a non-perturbative lattice study of mathrm {SU}(4) gauge theory with two flavors of fermions in the fundamental representation and two in the two-index antisymmetric representation: a theory closely related to a minimal partial-compositeness model for physics beyond the Standard Model, that was proposed by Ferretti. We discuss the phase structure of the lattice theory and report results for various observables of interest, including the masses of states obtained from different combinations of valence fermions and the spectrum of the Dirac operator. Finally, we comment on the extension of this type of studies to other partial-compositeness models (including, in particular, one that was recently suggested by Gertov et al.), which could admit lighter top-quark partners, highlighting some key features of our lattice simulation algorithm, that make it suitable for such generalizations.
Highlights
The experimental observation of a particle compatible with the Standard-Model Higgs boson at the Large Hadron Collider (LHC) [1,2] and the lack of evidence of any New Physics are putting very tight constraints on theories beyond the Standard Model
We present a non-perturbative lattice study of SU(4) gauge theory with two flavors of fermions in the fundamental representation and two in the two-index antisymmetric representation: a theory closely related to a minimal partial-compositeness model for physics beyond the Standard Model, that was proposed by Ferretti
Other unsatisfactory aspects of the Standard Model include the absence of unification of the gauge interactions, the “strong-CP problem” of quantum chromodynamics (QCD), and the fact that it does not include a proper quantum formulation of gravity
Summary
The experimental observation of a particle compatible with the Standard-Model Higgs boson at the Large Hadron Collider (LHC) [1,2] and the lack of evidence of any New Physics are putting very tight constraints on theories beyond the Standard Model. For technical reasons (related to the computational cost of the fermionic-matter content of the theory), it is more convenient to study first a closely related theory, with two flavors of Dirac fermions in the twoindex antisymmetric representation of SU(4), and two flavors of Dirac fermions in the fundamental representation of the gauge group With such matter contents, the theory will undergo a different symmetry-breaking pattern (in particular, one which can not accommodate a state with quantum numbers compatible with those of the Standard-Model Higgs boson); it remains an interesting theoretical laboratory, in which the main features of the actual model discussed in Ref.
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