  Cosmic ray anomalies observed by PAMELA and Fermi-LAT experiments may be
interpreted by heavy (TeV-scale) dark matter annihilation enhanced by
Sommerfeld effects mediated by a very light (sub-GeV) U(1)_X gauge boson, while
the recent direct searches from CoGeNT and DAMA/LIBRA experiments may indicate
a rather light (\sim 7 GeV) dark matter with weak interaction. Motivated by
these apparently different scales, we consider a gauge mediated next-to-the
minimal supersymmetric standard model (NMSSM) entended with a light U(1)_X
sector plus a heavy sector (\bar H_h,H_h), which can provide both a light (\sim
7 GeV) and a heavy (TeV-scale) dark matter without introducing any ad hoc new
scale. Through the Yukawa coupling between H_h and the messager fields, the
U(1)_X gauge symmetry is broken around the GeV scale radiatively and a large
negative m_S^2 is generated for the NMSSM singlet S. Furthermore, the small
kinetic mixing parameter between U(1)_X and U(1)_Y is predicted to be
\theta\sim 10^{-5}-10^{-6} after integrating out the messengers. Such a light
dark matter, which can have a normal relic density from the late decay of the
right-handed sneutrino (assumed to be the ordinary next-to-the lightest
supersymmetric particle and thermally produced in the early universe), can
serve a good candidate to explain the recent CoGeNT and DAMA/LIBRA results.
