Related papers: An extension of the standard model with a single c…
It is pointed out that in supersymmetric models with a new gauge symmetry under which the Higgs is charged, the fine-tuning of the electroweak symmetry breaking is relaxed due to suppression of the top Yukawa coupling at higher scales by a…
We investigate the prospects to achieve unification of the gauge couplings in models without supersymmetry. We restrict our discussion to $SU(5), SO(10)$ and $E_6$ models that mimic the structure of the Standard Model as much as possible…
In this paper, we study the renormalizability of the Standard Model in the Landau gauge. On the basis of the Ward-Takahashi identities, we derive exact expressions for the physical masses of the W and Z as well as the renormalized coupling…
We present the full one-loop correction to the relation between the running MSbar Yukawa coupling, $\overline h_f(\mu)$, at some renormalization scale, $\mu$, and the pole mass, $m_f$, of a fermion, $f$, in the standard model. Our result…
We apply the method of reduction of couplings in a Finite Unified Theory and in the MSSM. The method consists on searching for renormalization group invariant relations among couplings of a renormalizable theory holding to all orders in…
The scattering of longitudinally polarized W bosons in extensions of the Standard Model with anomalous Higgs couplings to the gauge sector and higher order $O(p^4)$ operators is considered. The modified couplings should be thought as the…
In this article we study a Standard Model extension modifying the top-quark Yukawa coupling to the Higgs boson by allowing a mixture of CP-odd and -even couplings. Single top-quark production in association with an additional Higgs boson…
In the Yukawa model with two different mass scales the renormalization group equation is used to obtain relations between scattering amplitudes at low energies. Considering fermion-fermion scattering as an example, a basic one-loop…
In this work some aspects of models with universal extra dimensions are studied. In particular, in the case of models with one universal extra dimension their phenomenology is investigated and used to extract bounds on the size of the extra…
We present a Z_6 orbifold compactification of the E_8xE_8 heterotic string which leads to the (supersymmetric) Standard Model gauge group and matter content. The quarks and leptons appear as three 16-plets of SO(10), whereas the Higgs…
Unitarity constraints for Yukawa couplings are considered in the Two Higgs Doublet Model type III, by using a general expansion in partial waves for fermionic scattering processes. Constraints over general Flavor Changing Neutral Currents…
We present a pedagogical case study how to combine micro-causality and unitarity based on a perturbative approach. The method we advocate constructs an analytic extrapolation of partial-wave scattering amplitudes that is constrained by the…
Several parameters of the minimal supergravity model are estimated by the method of the renormalization group. In this model, five arbitrary parameters $(m_0, m_{1/2}, \tan{\beta}, A_0, {sig}(\mu))$ are contained. $\tan{\beta}$ is evaluated…
We derive predictions for Yukawa coupling ratios within GUTs generated from operators with mass dimension four and five. These relations are a characteristic property of unified flavour models and can reduce the large number of free…
In this paper we investigate a natural extension of the Standard Model that involves varying coupling constants. This is a general expectation in any fundamental theory such as string theory, and there are good reasons for why new physics…
With a modest revision of the mass sector of the Standard Model, the systematics of the fermion masses and mixings can be fully described and interpreted as providing information on matrix elements of physics beyond the Standard Model. A…
Methods of determination of constants of the Standard Model are considered. The constants values obtained now are presented and experiments for improving some values are pointed out. A few possible generalized models are considered together…
Unification of the interactions of the Standard Model is possible in its simplest supersymmetric extension. The implications of the $\lambda _t$ fixed-point solution on the top mass and on Higgs phenomenology is discussed. Expected…
The matter content of the Standard Model admits a global symmetry due to the generational structure of the spectrum respected by all interactions except for fermion couplings to the Higgs doublet. This symmetry is identified as the largest…
We investigate whether or not perturbative unitarity is preserved in the Unhiggs model for the scattering process of heavy quarks and longitudinal gauge bosons $\bar q q \to V_L^+ V_L^-$. With the Yukawa coupling given in the original…