Abstract: Weak scale supersymmetry (SUSY) has been, for many years, the dominant
paradigm for physics beyond the Standard Model and in fact the simplest model
predicted the Higgs mass to lie exactly in the range where it was discovered.
And yet the community seems discouraged as to the likelihood of SUSY due to
lack of superpartners at LHC and the somewhat large value of the Higgs mass:
these are thought to exacerbate the ``naturalness'' question.
A more nuanced evaluation of electroweak naturalness points to
a highly natural SUSY mass spectrum characterized by light Higgsino states
with mass ~100-300 GeV while the SUSY breaking scale lies
in the multi-TeV region. Such a spectrum of superparticles seems to emerge
from simple statistical ideas applied to the string theory landscape of vacua.
The natural SUSY particle mass spectrum
1. gives rise to distinctive SUSY signatures at LHC but
2. might also allow SUSY to escape LHC detection so that a
higher energy hadron collider may be needed.
The required light higgsino states should appear at
an e+e- collider operating at CM energy 400-600 GeV:
the International Linear Collider or ILC.
Requiring naturalness also in the QCD sector, one expects two dark matter
particles: the axion along with a higgsino-like neutralino where typically
the axion makes up the bulk of dark matter.
Detection of a higgsino-like WIMP is ultimately expected while the axion
would have a suppressed coupling to photons which makes its detection
more challenging than was previously expected.