Prospects for Higgs coupling measurements in SUSY with radiatively-driven naturalness

In the post-LHC8 world—where a Standard Model-like Higgs boson has been established but there is no sign of supersymmetry (SUSY)—the detailed profiling of the Higgs boson properties has emerged as an important road towards discovery of new physics. We present calculations of the expected deviations in Higgs boson couplings ${\kappa }_{\tau ,b}$, ${\kappa }_t$, ${\kappa }_{W,Z}$, ${\kappa }_g$ and ${\kappa }_{\gamma }$ versus the naturalness measure ${\mathrm{\Delta }}_{\mathrm{EW}}$. Low values of ${\mathrm{\Delta }}_{\mathrm{EW}}\sim 10–30$ give rise to a natural little hierarchy characterized by light Higgsinos with a mass of $\mu \sim m_Z$ while top squarks are highly mixed but lie in the several TeV range. For such models with radiatively driven naturalness, one expects the Higgs boson $h$ to look very SM-like although deviations can occur. The more promising road to SUSY discovery requires direct Higgsino pair production at a high energy $e^{+}{e}^{-}$ collider operating with the center-of-mass energy $\sqrt{s}>2\mu \sim \sqrt{2{\mathrm{\Delta }}_{\mathrm{EW}}}{m}_Z$.