The possibility of the presence of a light pseudoscalar with the mass of 28 GeV in the MSSM Higgs sector extended by dimension-six operators is analyzed. The perturbative unitarity and vacuum stability constraints are discussed. Tree-level production cross sections of a light pseudoscalar in the process gg → µµbb−, and cross sections of a light pseudoscalar production in the topquark decay are evaluated for suitable benchmark points.
A non-minimal approximation for effective masses of light and heavy neutrinos in the framework of a type-I seesaw mechanism with three generations of sterile Majorana neutrinos which recover the symmetry between quarks and leptons is considered. The main results are: (a) the next-order corrections to the effective mass matrix of heavy neutrinos due to terms O(θMD) are obtained, which modify the commonly used representation for the effective mass (MD is a Dirac neutrino mass when the electroweak symmetry is spontaneously broken); and (b) the general form of the mixing matrix is found in non-minimal approximation parametrized by a complex 3×3 matrix satisfying a nontrivial constraint. Numerical analysis within the νMSM framework demonstrates the very small effect of new contributions of direct collider observables as opposed to their possible significance for cosmological models.
Higgs sector of the minimal supersymmetric standard model (MSSM) extended by dimension-six operators, which are loop contributions in the expansion of the Coleman-Weinberg type potential, is considered. The presence of such additional contributions allows the reopening of phenomenological MSSM scenarios closed in the previous analysis. In order to restrict respective MSSM parameter regions, perturbative unitarity constraints must be satisfied. We find the analytical formula for quartic and trilinear couplings for the Higgs potential extended by dimension-six operators, compare results with the loop corrected constraints at high or finite
s
with and without additional U
(6)-contributions, and show how the allowed regions in the parameter space are affected in these cases.
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