A family-universal anomalous U(1) in string models as the origin of supersymmetry breaking and squark degeneracy

Abstract

Recently a promising mechanism for supersymmetry breaking that utilizes both an anomalous U(1) gauge symmetry and an effective mass term m ∼ 1 Tev of certain relevant fields has been proposed. In this paper we examine whether such a mechanism can emerge in superstring-derived free fermionic models. We observe that certain three-generation string solutions, though not all, lead to an anomalous U(1) which couples universally to all three families. The advantages of this three-family universality of U(1) A , compared to the two-family case, proposed in earlier works, in yielding squark degeneracy, while avoiding radiative breaking of color and charge, are noted. The root cause of the flavor universality of U(1) A is the cyclic permutation symmetry that characterizes the Z 2 × Z 2 orbifold compactification with standard embedding, realized in the free fermionic models by the NAHE set. It is shown that non-renormalizable terms which contain hidden-sector condensates, generate the required suppression of the relevant mass term m, compared to the Planck scale. While the D-term of the family-universal U(1) A leads to squark degeneracy, those of the family-dependent U(1)' s, remarkably enough, are found to vanish for the solutions considered, owing to minimization of the potential. Motivations are provided for the combined U(1) A -Dilaton SUSY breaking.