Radiative Electroweak Symmetry Breaking and the Infrared Fixed Point of the Top Quark Mass

The infrared quasi fixed point solution for the top quark mass in the Minimal Supersymmetric Standard Model explains in a natural way large values of the top quark mass and appears as a prediction in many interesting theoretical schemes. Moreover, as has been recently pointed out, for moderate values of tan β, in order to achieve gauge and bottom-tau Yukawa coupling unification, the top quark mass must be within 10% of its fixed point value. In this work we show that the convergence of the top quark mass to its fixed point value has relevant consequences for the (assumed) universal soft supersymmetry breaking parameters at the grand unification scale. In particular, we show that the low energy parameters do not depend on A0 and B0 but on the combination δ = B0 − A0/2. Hence, there is a reduction in the number of independent parameters. Most interesting, the radiative SU(2)L × U(1)Y breaking condition implies strong correlations between the supersymmetric mass parameter μ and the supersymmetry breaking parameters δ and M1/2 or m0. These correlations, which become stronger for tan β < 2, may have some fundamental origin, which would imply the need of a reformulation of the naive fine tuning criteria. CERN-TH.7060/93 October 1993 ∗On leave of absence from the Institute of Theoretical Physics, Warsaw University