\simeq 2M_{0} \nonumber \\
m_{1}^{2}&\simeq &m_{0}^{2}+\frac{1}{2}M_{0}^{2} \ \ \ \ 
m_{2}^{2}\simeq -\frac{m_{0}^{2}}{2}-3M_{0}^{2} \ \ \ \ 
m_{S}^{2}\simeq m_{0}^{2} \nonumber \\
m_{T}^{2}&\simeq &4M_{0}^{2} \ \ \ \ \ \ \  
m_{Q_3}^{2}\simeq \frac{1}{2}m_{0}^{2}+6M_{0}^{2} \label{crit}\end{aligned}$$

1truecm

[Mass spectrum in the Higgs sector and vacuum structure]{} {#sec:mass}
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Let us first restrict the discussion to the physically relevant vacua with (real) v.e.v.’s for the field $\left\langle
H_{2}^{0}\right\rangle =h_{2},\left\langle H_{1}^{0}\right\rangle
=h_{1},\left\langle S\right\rangle =s.$ The scalar potential restricted to this sector reads $\left( \overline{g}^{2}=g_{1}^{2}+g_{2}^{2}\right) $

$$\begin{aligned}
V &=&\left( \kappa S^{2}+\lambda H_{1}^{0}H_{2}^{0}\right) ^{2}+\lambda
^{2}\left| S\right| ^{2}\left( \left| H_{1}^{0}\right| ^{2}+\left|
H_{2}^{0}\right| ^{2}\right) +  \nonumber \\
&&+\left( A_{\lambda }\lambda SH_{1}^{0}H_{2}^{0}+A\kappa \frac{\kappa }{3}%
S^{3}+h.c.\right) +m_{1}\left| H_{1}^{0}\right| ^{2}+m_{2}^{2}\left|
H_{2}^{0}\right| ^{2}+\nonumber \\
&&+m_{S}^{2}\left| S\right| ^{2}  
+\frac{\overline{g}^{2}}{4}\left( \left| H_{1}^{0}\right| ^{2}-\left|
H_{2}^{0}\right| ^{2}\right) ^{2}+V_{\mathrm{rad}}  \label{F}\end{aligned}$$

where $V_{\mathrm{rad}}$ is the quantum correction to the effective scalar potential beyond the RGE effects included in the running parameters of (\[F\]). These radiative corrections are important, in particular in the evaluation of the lightest Higgs boson mass. The relevant contribution comes from the top-stop sector because of the relatively large value of the top Yukawa coupling. Hence we only include the top quark and the two stop states, $T_{1}\ \mathrm{and}%
\ T_{2}$ in the usual Coleman-Weinberg expression,

$$V_{\mathrm{rad}}=\frac{1}{64\pi 