Light WIMP Searches: The Effect of the Uncertainty in Recoil Energy
  Scale and Quenching Factor
  Taking liquid xenon detectors as a case study, the importance of a robust
recoil energy calibration as a prerequisite to a search for light-mass Weakly
Interacting Massive Particles (WIMPs) is emphasized. Important shortfalls in
the analysis of existing measurements of the relative scintillation efficiency
and ionization yield for nuclear recoils in liquid xenon are described, leading
to the conclusion that recent attempts to extract light-WIMP sensitivity limits
from the XENON10 and XENON100 detectors are premature and overly optimistic.
