  We examine whether the cosmic ray positron excess observed by PAMELA can be
explained by neutralino annihilation in the Next-to-Minimal Supersymmetric
Standard Model (NMSSM). The main dark matter annihilation products are the
lightest CP-even scalar h1 plus the lightest CP-odd scalar a1, with the a1
decaying into two muons. The energetic positrons needed to explain PAMELA are
thus obtained in the NMSSM simply from kinematics. The required large
annihilation cross section is obtained from an s-channel resonance with the
heavier CP-odd scalar a2. Various experiments constrain the PAMELA-favored
NMSSM parameter space, including collider searches for a light a1. These
constraints point to a unique corner of the NMSSM parameter space, having a
lightest neutralino mass around 160 GeV and a very light pseudoscalar mass less
than a GeV. A simple parameterized formula for the charge-dependent solar
modulation effects reconciles the discrepancy between the PAMELA data and the
estimated background at lower energies. We also discuss the electron and gamma
ray spectra from the Fermi LAT observations, and point out the discrepancy
between the NMSSM predictions and Fermi LAT preliminary results and possible
resolution. An NMSSM explanation of PAMELA makes three striking and uniquely
correlated predictions: the rise in the PAMELA positron spectrum will turn over
at around 70 GeV, the dark matter particle mass is less than the top quark
mass, and a light sub-GeV pseudoscalar will be discovered at colliders.
