Bounds from Stability and Symmetry Breaking on Parameters in the Two-Higgs-Doublet Potential

Abstract

The most general $SU(2)\times U(1)_Y$-symmetric quartic potential with two Higgs doublets, subject to an only softly broken discrete symmetry $(\phi_1,\phi_2)\to(-\phi_1,\phi_2)$, is considered. At tree-level, analytic bounds on the parameters are derived that ensure a stable vacuum, breaking $SU(2)\times U(1)_Y$ down to $U(1)_{em}$.Comment: from last year, but due to recent interest now on the e-print archive, 8 pages, no figures, plain late