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 sensitive dependence of the higgsino mass parameter $\mu$ and of the gaugino coupling strengths ${\tilde g}_{u,d}$, ${\tilde g}^\prime_{u,d}$ on the value of $Y_t$ in the vicinity of the Landau pole is a remarkable consequence. A few other interesting features emerge, though the model is found to be disfavored within the infrared fixed point scenario because of the need to have several fine tunings at work on account of the requirement of a low upper bound on $\tan\beta$.