Motivated by the recent PAMELA and ATIC data, one is led to a scenario with
heavy vector-like dark matter in association with a hidden U(1)X​ sector
below GeV scale. Realizing this idea in the context of gauge mediated
supersymmetry breaking (GMSB), a heavy scalar component charged under U(1)X​
is found to be a good dark matter candidate which can be searched for direct
scattering mediated by the Higgs boson and/or by the hidden gauge boson. The
latter turns out to put a stringent bound on the kinetic mixing parameter
between U(1)X​ and U(1)Y​: θ≲10−6. For the typical range
of model parameters, we find that the decay rates of the ordinary lightest
neutralino into hidden gauge boson/gaugino and photon/gravitino are comparable,
and the former decay mode leaves displaced vertices of lepton pairs and missing
energy with distinctive length scale larger than 20 cm for invariant lepton
pair mass below 0.5 GeV. An unsatisfactory aspect of our model is that the
Sommerfeld effect cannot raise the galactic dark matter annihilation by more
than 60 times for the dark matter mass below TeV.Comment: 1+15 pages, 4 figures, version published in JCAP, references added,
minor change