  As discussed recently by Hooper and Tait, the singlino-like dark matter in
the Minimal Supersymmetric Standard Model (MSSM) extended by a singlet Higgs
superfield can give a perfect explanation for both the relic density and the
Pamela result through the Sommerfeld-enhanced annihilation into singlet Higgs
bosons ($a$ or $h$ followed by $h->a a$) with $a$ being light enough to decay
dominantly to muons or electrons. In this work we analyze the parameter space
required by such a dark matter explanation and also consider the constraints
from the LEP experiments. We find that although the light singlet Higgs bosons
have small mixings with the Higgs doublets in the allowed parameter space,
their couplings with the SM-like Higgs boson $h_{SM}$ (the lightest
doublet-dominant Higgs boson) can be enhanced by the soft parameter $A_\kappa$
and, in order to meet the stringent LEP constraints, the $h_{SM}$ tends to
decay into the singlet Higgs pairs $aa$ or $hh$ instead of $b\bar b$. So the
$h_{SM}$ produced at the LHC will give a multi-muon signal, h_{SM} -> aa -> 4
muons or h_{SM} -> hh -> 4 a -> 8 muons.
