short account of this important matter here.

As for the particle spectrum, this model presents several new features as compared to the MSSM. The supermultiplet $S$ consists of two scalars of opposite CP and one Majorana fermion. After the $SU(2)\times U(1)$ breaking, these states get mixed with the neutral states in the Higgs doublet and gauge supermultiplets, leading to a slightly richer spectrum. In particular, since the visibility of physical states depends on their couplings to the gauge bosons and to matter, some particles could be relatively light if they are mainly gauge singlets. Thus, some of the limits on neutral particles obtained at LEP in the MSSM framework do not immediately apply to the alternative (M+1)SSM. The discussion in this paper as well as in our previous ones [@ERS1; @ERS2] is also aimed to persuade experimentalists to analyze their data on a more general basis.

In the $\kappa \rightarrow 0,\lambda \rightarrow 0$ limit, the gauge singlet decouples and the remaining theory looks like the MSSM [@Ellis]. However, this limit leads to a particular version of the MSSM with a strong correlation among the soft parameters, as we shall discuss later on. The singlet scalar takes a very large v.e.v. 