The first direct detection limits on dark matter in the MeV to GeV mass range are presented , using XENON10 data .
Such light dark matter can scatter with electrons , causing ionization of atoms in a detector target material and leading to single- or few-electron events .
We use 15 kg-days of data acquired in 2006 to set limits on the dark-matter–electron scattering cross section .
The strongest bound is obtained at 100 MeV where \sigma _ { e } < 3 \times 10 ^ { -38 } \mathrm { cm ^ { 2 } } at 90 % CL , while dark matter masses between 20 MeV and 1 GeV are bounded by \sigma _ { e } < 10 ^ { -37 } \mathrm { cm ^ { 2 } } at 90 % CL .
This analysis provides a first proof-of-principle that direct detection experiments can be sensitive to dark matter candidates with masses well below the GeV scale .