Natural supersymmetry without light Higgsinos

We present a mechanism that allows a large Higgsino mass without large fine-tuning. The Higgs is a pseudo-Nambu-Goldstone boson (PNGB) of the global symmetry breaking pattern $SO(5)\to SO(4)$. Because of the PNGB nature of the light Higgs, the $SO(5)$ invariant Higgsino mass does not directly contribute to the Higgs mass. Large couplings in the Higgs sector that spontaneously breaks $SO(5)$ minimize the tuning, and are also motivated by the requirements of generating a sufficiently large Higgs quartic coupling and of maintaining a natural approximate global $SO(5)$ symmetry. When these conditions are imposed, theories of this type predict heavy Higgsinos. This construction differs from composite Higgs models in that no new particles are introduced to form complete $SO(5)$ multiplets involving the top quark—the stop is the only top partner. Compatibility with Higgs coupling measurements requires cancellations among contributions to the Higgs mass-squared parameter at the 10% level. An important implication of this construction is that the compressed region of stop and sbottom searches can still be natural.

Figure 1

The left (right) panel shows ${\mathrm{\Delta }}_{\max }^{-1}$ ($T$) as a function of $\lambda$ for different values of $\tan \beta$ given on each curve. The other fixed parameters are given in the text.

Figure 2

The left (right) panel shows ${\mathrm{\Delta }}_{\max }^{-1}$ ($T$) as a function of $\lambda$, for different values of $M_{\mathrm{SUSY}}$ given on each curve. At each point, $\tan \beta$ has been chosen to minimize the tuning. The other fixed parameters are given in the text.