An indirect probe of higgsino world at the CEPC

The higgsino world is one of the popular natural SUSY scenarios, in which $|\mu| \ll M_{gauginos} \ll M_{scalars}$. As such, searching for light degenerate higgsinos becomes an essential task of testing naturalness in supersymmetry (SUSY). In this work, we study the indirect effects of light higgsinos in the process $e^+e^- \to W^+W^-$ at future Higgs factories, such as Circular Electron Positron Collider (CEPC) in China. we find that the higgsino mass parameter $\mu \lesssim 210$ GeV favored by naturalness can be covered if the accuracy of the measurement of $W^+W^-$ production can reach 0.1\% at 240 GeV CEPC.