Supersymmetric vacuum alignment, chiral fermions, quark-lepton universality and MW/(MZ cos θW)

Abstract

Implicit global symmetries of the standard model, such as the SU(4) underlying quark-lepton universality or the custodial SU(2) responsible for rho =MW/MZ cos theta W=1, as well as the chiral spectrum of quarks and leptons, can be explained by the dynamics of vacuum alignment in supersymmetric composite models. The general theory of supersymmetric vacuum alignment is summarised and a simple formula is derived which determines the alignment in the presence of gauge fields, including a Fayet-Iliopoulos U(1) (1974). In the one-generation preon model of Barbieri, Masiero and Veneziano (1983), this resolution of the vacuum alignment problem requires the enlargement of the standard model gauge group to include chiral colour and extra U(1) factors. These extra gauge groups are all spontaneously broken, leaving a light fermion spectrum comprising only quarks, leptons and leptoquarks.