Weakly Interacting Massive Particles ( WIMPs ) are one of the leading candidates for Dark Matter .
We develop a model–independent method for determining the mass m _ { \chi } of the WIMP by using data ( i.e. , measured recoil energies ) of direct detection experiments .
Our method is independent of the as yet unknown WIMP density near the Earth , of the form of the WIMP velocity distribution , as well as of the WIMP–nucleus cross section .
However , it requires positive signals from at least two detectors with different target nuclei .
In a background–free environment , m _ { \chi } \sim 50 GeV could in principle be determined with an error of \sim 35 \% with only 2 \times 50 events ; in practice upper and lower limits on the recoil energy of signal events , imposed to reduce backgrounds , can increase the error .
The method also loses precision if m _ { \chi } significantly exceeds the mass of the heaviest target nucleus used .