Spin-dependent WIMPs in DAMA?
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 gtrsim20 GeV by the null result with the DAMA Xe detector. A SD WIMP with mass lesssim20 GeV is still compatible, but only if the SD WIMP-neutron interaction is four orders of magnitude greater than the WIMP-proton interaction.
Additional Information© 2001 SISSA Received 8 July 2001, accepted for publication 27 July 2001. Published 9 August 2001 We thank J. Edsjö for useful discussions. This work was supported in part by NSF AST-0096023, NASA NAG5-8506, and DoE DE-FG03-92-ER40701 and DE-FG03-88-ER40397.
Published - ULLjhep01a.pdf