Phenomenological constraints on superstring models with intermediate-mass scales

Abstract

The mechanism for generating radiatively the breaking of the gauge symmetry at an intermediate-mass scale, in the framework ofE 6 superstring-inspired models, is discussed in the case where the light standard-model singlets from the additional $$b_{1,1} \left( {\underline {27} + \overline {\underline {27} } } \right)$$ pairs interact with the fields of then g generations of27, through both renormalizable and non-renormalizable couplings. The minimization of the effective scalar potential is worked out in a specific model, based on the gauge groupSU(3)c×SU(2)L×U(1) Y ×U(1) E . The resultant mixings among the various fields are analysed, pointing out the consequences for the problem of proton decay: it is shown that this problem cannot be solved together with that of the neutrino mass, without involving some discrete symmetry.