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Quasi-fixed point scenarios and the Higgs mass in the E6 inspired SUSY models

We analyse the two-loop renormalization group (RG) flow of the gauge and Yukawa couplings within the E6 inspired supersymmetric (SUSY) models with extra U(1)_{N} gauge symmetry under which right-handed neutrinos have zero charge. In these models single discrete \tilde{Z}^{H}_2 symmetry forbids the tree-level flavor-changing transitions and the most dangerous baryon and lepton number violating operators. We consider two different scenarios A and B that involve extra matter beyond the MSSM contained in three and four 5+\overline{5} representations of SU(5) respectively plus three SU(5) singlets which carry U(1)_{N} charges. In the scenario A the measured values of the SU(2)_W and U(1)_Y gauge couplings lie near the fixed points of the RG equations. In the scenario B the contribution of two--loop corrections spoils the unification of gauge couplings resulting in the appearance of the Landau pole below the Grand Unification scale M_X. The solutions for the Yukawa couplings also approach the quasi fixed points with increasing their values at the scale M_X. We calculate the two--loop upper bounds on the lightest Higgs boson mass in the vicinity of these quasi fixed points and compare the results of our analysis with the corresponding ones in the NMSSM. In all these cases the theoretical restrictions on the SM--like Higgs boson mass are rather close to 125 GeV.