The possibility of identification of an observable CMS $mu^+ mu^-$ excess at 28 GeV in the channel $ppto mu^+ mu^- b bar b$ at $sqrt{s}$=8 TeV and 13 TeV as a manifestation of one of the minimal supersymmetric standard model (MSSM) Higgs bosons is in
vestigated. The MSSM parametric scenarios in the regime of large threshold corrections involving low-mass CP-odd scalar, a 125 GeV CP-even scalar and other Higgs bosons with suitable masses are found, where the alignment limit conditions for the Higgs couplings are respected. Perturbative unitarity bounds and constraints on the electroweak vacuum stability are discussed in the regime of substantial couplings with the top- and bottom superpartners. LHC phenomenology including top-quark decay in such a regime is analyzed.
Possible realistic scenarios are investigated in the minimal supersymmetric standard model (MSSM) Higgs sector extended by dimension-six effective operators. The CP-odd Higgs boson with low mass around 30--90 GeV could be consistently introduced in t
he regime of large threshold corrections to the effective MSSM two-doublet Higgs potential.
In the framework of the effective field theory approach to heavy supersymmetry radiative corrections in the Higgs sector of the Minimal Supersymmetric Standard Model (MSSM) for the effective potential decomposition up to the dimension-six operators a
re calculated. Symbolic expressions for the threshold corrections induced by $F$- and $D$- soft supersymmetry breaking terms are derived and the Higgs boson mass spectrum respecting the condition $m_h=$125 GeV for the lightest $CP$-even scalar is evaluated.
We consider the K^0 - bar K^0 and B^0 - bar B^0 mixings in the MSSM with the two-Higgs-doublet scalar sector featuring explicit CP violation, and the Yukawa sector of type II. In the case of strong mixing between CP-odd and CP-even states the existen
ce of light charged Higgs is allowed in the model. The mass splitting Delta m_{LS} and the amount of indirect CP violation epsilon are calculated. In the limit of effective low-energy approximation the nonstandard effects are shown to be negligibly small in Delta m_{LS} and epsilon for the K^0-mesons, being almost independent on the charged Higgs boson mass. However, for the B_d^0 - bar B_d^0 and B_s^0 - bar B_s^0 systems the effects of nonstandard physics are shown to be larger, limiting the MSSM parameter space.
The Wtb vertex can be probed on future colliders in the processes of single top production (LHC, pp mode, NLC, $gamma e$ mode) and of top pair production (NLC, e^+ e^- mode). We analyse observables sensitive to anomalous Wtb couplings in the top pair
production process of e^+ e^- collisions. In particular, forward-backward and spin-spin asymmetries of the top decay products and the asymmetry of the lepton energy spectum are considered. Possible bounds on anomalous couplings obtained are competitive to those expected from the upgraded Tevatron and LHC. The validity of the infinitely small width approximation for the three-body top decay is also studied in detail.
In the case of minimal supersymmetric extension of the Standard Model (MSSM), when the pseudoscalar Higgs boson mass is less than the supersymmetry energy scale, the effective theory at the electroweak scale is a two-Higgs-doublet model. We diagonali
ze the mass matrix of the general two-Higgs-doublet model, expressing Higgs boson self-couplings in terms of two mixing angles and four Higgs boson masses, and derive in a compact form the complete set of Feynman rules, including quartic couplings in the Higgs sector, for the case of CP-violating potential. Some processes of double and triple Higgs boson production at a high-energy linear collider are calculated in the case of mixing angles and scalar boson masses satisfying the MSSM constraints.
