  Existence of a mirror world in the universe is a fundamental way to restore
the observed parity violation in weak interactions and provides the lightest
mirror nucleon as a unique GeV-scale dark matter particle candidate. The
visible and mirror worlds share the same spacetime of the universe and are
connected by a unique space-inversion symmetry -- the mirror parity (P). We
conjecture that the mirror parity is respected by the fundamental interaction
Lagrangian, and study its spontaneous breaking from minimizing the Higgs vacuum
potential. The domain wall problem is resolved by a unique soft breaking
linear-term from the P-odd weak-singlet Higgs field. We also derive constraint
from the Big-Bang nucleosynthesis. We then analyze the neutrino seesaw for both
visible and mirror worlds, and demonstrate that the desired amounts of visible
matter and mirror dark matter in the universe arise from a common origin of CP
violation in the neutrino sector via leptogenesis. We derive the Higgs
mass-spectrum and Higgs couplings with gauge bosons and fermions. We show their
consistency with the direct Higgs searches and the indirect precision
constraints. We further study the distinctive signatures of the predicted
non-standard Higgs bosons at the LHC. Finally, we analyze the direct detections
of GeV-scale mirror dark matter by TEXONO and CDEX experiments.
