In supersymmetric models with radiatively driven naturalness and light Higgsinos, the top squarks may lie in the 0.5–3 TeV range, and thus, only a fraction of natural parameter space is accessible to LHC searches. We outline the range of top squark and lightest SUSY particle masses preferred by electroweak naturalness in the standard parameter space plane. We note that the branching fraction for $b\to s\gamma$ decay favors top squarks much heavier than 500 GeV. Such a range of top squark mass values is in contrast to previous expectations where $m(\text{stop})<500\mathrm{GeV}$ had been considered natural. In radiative natural SUSY, top squarks decay roughly equally via ${\tilde{t}}_1\to b{\tilde{W}}_1$ and $t{\tilde{Z}}_{1,2}$ where ${\tilde{W}}_1$ and ${\tilde{Z}}_{1,2}$ are Higgsino-like electroweakinos. Thus, top squark pair production should yield all of $t\overline{t}+E_T^{\text{miss}}$, $t\overline{b}+E_T^{\text{miss}}$, $b\overline{t}+E_T^{\text{miss}}$ and $b\overline{b}+E_T^{\text{miss}}$ signatures at comparable rates. We propose that future LHC top squark searches take place within a semisimplified model which corresponds more closely to expectations from theory.

• Received 1 December 2016
• Corrected 19 March 2021

DOI:https://doi.org/10.1103/PhysRevD.95.055012