We investigate whether the annual modulation observed in the DAMA experiment
can be due to a weakly-interacting massive particle (WIMP) with an axial-vector
(spin-dependent; SD) coupling to nuclei. We evaluate the SD WIMP-proton cross
section under the assumption that such scattering accounts for the DAMA
modulation, and we do the same for a SD WIMP-neutron cross section. We show
that SD WIMP-proton scattering is ruled out in a model-independent fashion by
null searches for energetic neutrinos from WIMP annihilation in the Sun, and
that SD WIMP-neutron scattering is ruled out for WIMP masses > 20 GeV by the
null result with the DAMA Xe detector. A SD WIMP with mass < 20 GeV is still
compatible, but only if the SD WIMP-neutron interaction is four orders of
magnitude greater than the WIMP-proton interaction.Comment: 4 pages, 2 figure
