XENON10/100 dark matter constraints in comparison with CoGeNT and DAMA: Examining the Leff dependence

We consider the compatibility of DAMA/LIBRA, CoGeNT, XENON10 and XENON100 results for spin-independent (SI) dark matter weakly interacting massive particles, particularly at low masses (similar to 10 GeV), assuming a standard dark matter halo. The XENON bounds depend on the scintillation efficiency factor L-eff for which there is considerable uncertainty. Thus we consider various extrapolations for L-eff at low energy. With the L-eff measurements we consider, XENON100 results are found to be insensitive to the low-energy extrapolation. We find the strongest bounds are from XENON10, rather than XENON100, due to the lower energy threshold. For reasonable choices of L-eff and for the case of SI elastic scattering, XENON10 is incompatible with the DAMA/LIBRA 3 sigma region and severely constrains the 7-12 GeV WIMP mass region of interest published by the CoGeNT Collaboration.