SYMMETRY PRINCIPLES TOWARD SOLUTIONS OF THE μ PROBLEM

We stress that a natural solution of the μ problem requires two ingredients: a symmetry that would enforce μ=0 as well as the occurrence of a small breaking parameter that generates a nonzero μ. It is suggested that both the Peccei-Quinn symmetry and the spontaneously broken R symmetry may be the sources of the needed μ term in the minimal supersymmetric standard model provided that they are spontaneously broken at a scale 10 10 –10 12 GeV . To solve the strong CP problem with a hidden sector confining group, both of these symmetries are needed in superstring models with an anomalous U (1) A .