its dominant contributions from two sources, the coupling of the Higgs to gluons through a heavy quark loop and the direct coupling of the Higgs to strange quarks [@jungman]. That means that this coupling depends on the parameter $$f_{Ts} =  {\bra{p}  m_s \bar s s \ket{p} \over \bra{p}  H_{QCD}
                           \ket{p}} \ ,
\label{fTsdefin}$$ that is, the fraction of the mass of the proton that arises from the mass of the non-valence strange quarks in the proton wavefunction. It has been known for some time that there is significant uncertainty in this quantity [@KaplanNelson], and several recent papers have pointed out the uncertainty this introduces to calculations of the WIMP-nucleon elastic scattering cross section [@Bottino; @EllisUpdate]. In particular, in the case of WIMPs which couple dominantly to the strange content of the nucleon, this can lead to an uncertainty in the direct detection cross section of a factor of 4 or even larger [@Bottino]. It is possible that this uncertainty could be reduced in the future through the use of lattice gauge theory [@UKQCD; @Weise].

The processes of WIMP-nuclei elastic scattering can be naturally divided into spin-dependent and spin-independent contributions. The spin-independent, or coherent scattering, term is enhanced in WIMP-nucleus cross 