Using the energy spectrum measured by DAMA/LIBRA to probe light dark matter

A weakly interacting massive particle (WIMP) weighing only a few GeV has been invoked as an explanation for the signal from the DAMA/LIBRA experiment. We show that the data from DAMA/LIBRA are now powerful enough to strongly constrain the properties of any putative WIMP. Accounting for the detailed recoil spectrum, a light WIMP with a Maxwellian velocity distribution and a spin-independent interaction cannot account for the data. Even neglecting the spectrum, significant parameter space is excluded by a limit that can be derived from the DAMA unmodulated signal at low energies. Appreciable modification to the astrophysics or particle physics can open light mass windows.