What can 1970's Elastic Electron Scattering Experiments tell us about the Direct Detection of Dark Matter? ⁎

Theoretical calculations of neutralino cross sections with various nuclei are of great interest to direct dark matter searches such as CDMS, EDELWEISS, ZEPLIN, and other experiments. These cross sections and direct detection rates are generally computed with generic, one or two parameter model-dependent nuclear form factors; these form factors are usually analytic approximations to the fourier transform of two-parameter Fermi nuclear charge densities, and may not mirror the actual form factor for nuclei important in direct dark matter searches. Elastic electron scattering, largely compiled in the 1970s, can allow for very precise determinations of nuclear form factors and hence nuclear charge densities for spherical or near-spherical nuclei. We compare model independent form factors derived from elastic electron scattering data to commonly utilized model dependent form factors for various target nuclei important in dark matter searches, such as Si, Ge, S, Ca and others. We have found that for nuclear recoils in the range of 10–100 keV significant differences in cross sections and rates exist when the model independent form factors are used.