Light dark matter in the NMSSM: upper bounds on direct detection cross sections

In the Next-to-Minimal Supersymmetric Standard Model, a bino-like LSP can be as light as a few GeV and satisfy WMAP constraints on the dark matter relic density in the presence of a light CP-odd Higgs scalar. We study upper bounds on the direct detection cross sections for such a light LSP in the mass range 2-20GeV in the NMSSM, respecting all constraints from B-physics and LEP. The OPAL constraints on e(+)e(-) -> chi(0)(1)chi(0)(i) ( i > 1) play an important role and are discussed in some detail. The resulting upper bounds on the spin-independent and spin-dependent nucleon cross sections are similar to 10(-42) cm(2) and similar to 4 x 10(-40) cm(2), respectively. Hence the upper bound on the spin-independent cross section is below the DAMA and CoGeNT regions, but could be compatible with the two events observed by CDMS-II.