Model-independent comparison of annual modulation and total rate with direct detection experiments

The relative sensitivity of different direct detection experiments depends sensitively on the astrophysical distribution and particle physics nature of dark matter, prohibiting a model-independent comparison. The situation changes fundamentally if two experiments employ the same target material. We show that in this case one can compare measurements of an annual modulation and exclusion bounds on the total rate while making no assumptions on astrophysics and no (or only very general) assumptions on particle physics. In particular, we show that the dark matter interpretation of the DAMA/LIBRA signal can be conclusively tested with COSINUS, a future experiment employing the same target material. We find that if COSINUS excludes a dark matter scattering rate of about $0.01\,\text{kg}^{-1}\,\text{days}^{-1}$ with an energy threshold of $1.8\,$keV and resolution of $0.2\,$keV, it will rule out all explanations of DAMA/LIBRA in terms of dark matter scattering off sodium and/or iodine.