The particle discovered in the Higgs-boson searches at the LHC with a mass of about 125 GeV can be identified with one of the neutral Higgs bosons of the Nextto-Minimal Supersymmetric Standard Model (NMSSM). We calculate predictions for the Higgs-boson masses in the NMSSM using the Feynman-diagrammatic approach. The predictions are based on the full NMSSM one-loop corrections supplemented with the dominant and sub-dominant two-loop corrections within the Minimal Supersymmetric Standard Model (MSSM). These include contributions at, as well as a resummation of leading and subleading logarithms from the top/scalar top sector. Taking these corrections into account in the prediction for the mass of the Higgs boson in the NMSSM that is identified with the observed signal is crucial in order to reach a precision at a similar level as in the MSSM. The quality of the approximation made at the two-loop level is analysed on the basis of the full one-loop result, with a particular focus on the prediction for the Standard Model-like Higgs boson that is associated with the observed signal. The obtained results will be used as a basis for the extension of the code FeynHiggs to the NMSSM.

The NMSSM represents an elegant and well motivated description for the observed phenomenology in high energy physics. In this model a scalar singlet together with its superpartner is added to the Higgs sector of the Minimal Supersymmetric Standard Model (MSSM). In order to compare the NMSSM with experimental data at the same level of accuracy as the MSSM, precise predictions for Higgs-boson masses in the NMSSM are a necessity. This work will focus on the prediction for the Higgs masses in the NMSSM at one-and two-loop order obtained by Feynman diagrammatic methods. While the one-loop calculation is performed in the full NMSSM, the two-loop contributions to the Higgs-boson self-energies are approximated by their MSSM counterparts. It is shown that in this way the two-loop contributions are well approximated for a wide range of parameters. The results are exemplified for an example scenario genuine to the NMSSM.

The interpretation of the Higgs signal at ∼ 126 GeV within the Minimal Supersymmetric Standard Model (MSSM) depends crucially on the predicted properties of the other Higgs states of the model, as the mass of the charged Higgs boson, M H ± . This mass is calculated in the Feynman-diagrammatic approach within the MSSM with real parameters. The result includes the complete one-loop contributions and the twoloop contributions of O(α t α s ). The one-loop contributions lead to sizable shifts in the M H ± prediction, reaching up to ∼ 8 GeV for relatively small values of M A . Even larger effects can occur depending on the sign and size of the µ parameter that enters the corrections affecting the relation between the bottom-quark mass and the bottom Yukawa coupling. The two-loop O(α t α s ) terms can shift M H ± by more than 2 GeV. The two-loop contributions amount to typically about 30% of the one-loop corrections for the examples that we have studied. These effects can be relevant for precision analyses of the charged MSSM Higgs boson. *

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