Origins of the Isospin Violation of Dark Matter Interactions
  Light dark matter (DM) with a large DM-nucleon spin-independent cross section
and furthermore proper isospin violation (ISV) $f_n/f_p\approx-0.7$ may provide
a way to understand the confusing DM direct detection results. Combing with the
stringent astrophysical and collider constraints, we systematically investigate
the origin of ISV first via general operator analyses and further via
specifying three kinds of (single) mediators: A light $Z'$ from chiral
$U(1)_X$, an approximate spectator Higgs doublet (It can explain the $W+jj$
anomaly simultaneously) and color triplets. In addition, although $Z'$ from an
exotic $U(1)_X$ mixing with $U(1)_Y$ generating $f_n=0$, we can combine it with
the conventional Higgs to achieve proper ISV. As a concrete example, we propose
the $U(1)_X$ model where the $U(1)_X$ charged light sneutrino is the inelastic
DM, which dominantly annihilates to light dark states such as $Z'$ with sub-GeV
mass. This model can address the recent GoGeNT annual modulation consistent
with other DM direct detection results and free of exclusions.
