Infrared fixed point of the top Yukawa coupling in split supersymmetry

Abstract

The severe constraints imposed on the parameter space of the minimal split supersymmetry model by the infrared fixed point solution of the top Yukawa coupling Y_t are studied in detail in terms of the value of the top quark mass measured at the Tevatron together with the lower bound on the lightest Higgs mass established by LEP. The dependence of the higgsino mass parameter μ, the gaugino coupling strengths g̅_u,d, g̅'_u,d and of the Higgs quartic self coupling λ on the value of Y_t in the vicinity of the Landau pole is discussed. A few interesting features emerge, though the model is found to be disfavored within the infrared fixed point scenario because of the need to have several unnatural cancellations at work on account of the requirement of a low upper bound on tanβ.