Related papers: The Limits of Custodial Symmetry
In the present work, we elucidate the meaning of the custodial symmetry and its importance at the phenomenological level in the framework of the standard model of the electroweak interactions and its possible extensions.
The triviality of the scalar sector of the standard one-doublet Higgs model implies that it is only an effective low-energy theory valid below some cut-off scale $\Lambda$. In this note we show that the experimental constraint on the amount…
Custodial Naturalness is a recently introduced idea that combines conformal and scalar-sector custodial symmetry to address the electroweak (EW) scale hierarchy problem of the Standard Model (SM). We introduce a new model that realizes…
The Georgi-Machacek model adds two SU(2)_L-triplet scalars to the Standard Model in such a way as to preserve custodial SU(2) symmetry. We study the generalizations of the Georgi-Machacek model to SU(2)_L representations larger than…
We study precision electroweak constraints within a RS1 model with gauge fields and fermions in the bulk. The electroweak gauge symmetry is enhanced to SU(2)_L \times SU(2)_R \times U(1)_{B-L}, thereby providing a custodial isospin symmetry…
We present a particular warped extra dimensional model, where the flavour diagonal and flavour non-diagonal Z boson couplings to left-handed down quarks are protected by the custodial symmetry P_LR. After a brief introduction of the model…
A well known problem in supersymmetric models is the presence of, lepton and baryon number violating, dimension four operators. The traditional R parity solution may not be suitable if one tries to incorporate supersymmetry into a Planck…
We study the $SU(3)_L\otimes U(1)_X$ extension of the Standard model with a strong U(1) coupling. We argue that current experiments limit this coupling to be relatively large. The model is dynamically broken to the Standard $SU(2)_L \otimes…
We present the electroweak and flavour structure of a model with a warped extra dimension and the bulk gauge group SU(3) x SU(2)_L x SU(2)_R x P_LR x U(1)_X. The presence of SU(2)_R implies an unbroken custodial symmetry in the Higgs system…
We present a simple and transparent method to study custodial symmetry in the Two-Higgs-Doublet Model. The method allows to formulate the basis independent, sufficient and necessary, conditions for the custodial symmetry of the scalar…
Integrating out a heavy scalar can cause the Higgs trilinear coupling to deviate from its Standard Model value: a good example is provided by an $SU(2)$ quadruplet. Constraints on the full theory, however, can limit the size of the…
In extending the minimal standard model of quarks and leptons to include supersymmetry, the conservation of baryon and lepton numbers is no longer automatic. I show how the latter may be achieved with a new U(1) gauge symmetry and new…
The Randall-Sundrum scenario with Standard Model fields in the bulk and a custodial symmetry is considered. We determine the several minimal quark representations allowing to address the anomalies in the forward-backward b-quark asymmetry…
The Supersymmetric Custodial Triplet Model (SCTM) adds to the particle content of the MSSM three $SU(2)_L$ triplet chiral superfields with hypercharge $Y=(0,\pm1)$. At the superpotential level the model respects a global $SU(2)_L \otimes…
The generalization of the "custodial symmetry" mechanism which leads to the natural (without fine tuning) explanation of the doublet-triplet hierarchy is suggested in the frames of extended $SU(N\geq 8)$ SUSY GUTs. It is shown also that…
Standard Model may be defined with the additional discrete symmetry, i.e. with the gauge group $SU(3)\times SU(2) \times U(1)/{\cal Z}$ (${\cal Z} = Z_6$, $Z_3$ or $Z_2$) instead of the usual $SU(3)\times SU(2) \times U(1)$. It has the same…
We present a complete study of rare K and B meson decays in a warped extra dimensional model with a custodial protection of (both diagonal and non-diagonal) Z d_L^i \bar d_L^j couplings, including K^+ -> pi^+ nu anti-nu, K_L -> pi^0 nu…
A $SU(N)_L\times SU(N)_R$ gauge theory for a scalar multiplet $Y$ transforming in the bi-fundamental representation $(N,\bar N)$ preserves, for $N>4$, an accidental $U(1)$ symmetry firstly broken at operator dimension $N$. Two…
In this work we consider the extension of the standard model by dark fields with an Abelian $U(1)_{d}$ spontaneously broken gauge symmetry in a hidden dark matter scenario. Considering all the dimension four gauge invariant terms we show…
In the standard model the proton is protected from decay naturally by gauge symmetries, whereas in the ordinary minimal supersymmetric standard model an ad hoc discrete symmetry is imposed for the proton stability. We present a new…