Low Fine-Tuning with Heavy Higgsinos in Yukawa Unified SUSY GUTs

Abstract

The work presented considers a class of minimally constructed Yukawa unified SUSY GUTs - NUHM2 - and explore their implications when their soft supersymmetry breaking Lagrangian is generalized by the non-holomorphic terms which provide extra contributions to the Higgsino mass and couple the supersymmetric scalar fields to the wrong Higgs doublets. With such a simple extension, it can be found several regions with interesting implications which cannot be realized in the usual restricted models. It is observed that the Yukawa unification solutions can be compatible with relatively light mass spectrum and acceptable low fine-tuning measurements. In the restricted models such effects can directly be addressed to the non-holomorphic terms. They can provide a slight improvement in the SM-like Higgs boson mass without altering the mass spectrum too much, and they can accommodate relatively lighter sbottom and stau masses, while they do not change the stop sector much. The dark matter can be Higgsino-like or Bino-like, but the experimental relic density measurements favor the Higgsino-like dark matter, while the Bino-like dark matter is predicted with a quite large relic density. Also several coannihilation scenarios are identified in the Higgsino-like dark matter regions, while the Bino-like dark matter do not allow any of such coannihilation processes. The presence of the non-holomorphic terms can weaken the impact from the phenomenological or indirect constraints such as low fine-tuning, Yukawa unification and rare decays of $B-$meson, the direct and model independent constraints still yield a strong strike on the solutions. Such constraints are discussed in regard of the current collider analyses on $\tau\tau$ events and direct detection of dark matter experiments.