SABRE (Sodium iodide with Active Background REjection) is a dark matter direct-detection experiment that aims to check on the claim by the DAMA/LIBRA collaboration of a signal that is consistent with expectations based on the Earth moving through a dark-matter wind.

It will consist of two near-identical experiments, one (SABRE North) based in the northern hemisphere at the Laboratori Nazionale del Gran Sasso (LNGS) in Italy , and the other (SABRE South)at the Stawell Underground Physics Laboratory (SUPL) in Victoria, Australia.

Both experiments will utilise ultra-pure NaI crystals coupled to low-noise, high-sensitivity Photo-Multiplier Tubes (PMTs), and will also feature a surrounding liquid-scintillator-based veto system, in order to reduce greatly false signals due to radioactivity within the hardware itself, as well as in the environment.

Such experiments are located deep below ground in order to shield them as much as possible from naturally-occurring backgrounds, such as those generated by cosmic rays.

The two-hemisphere approach unique to SABRE is intended to distinguish possible environmental effects in the measured signals. The expected signal from a dark-matter wind is modulated with a one-year period (a result of the Earth’s orbital rotation around the Sun), and it is possible that some environmental factor, however unexpected, might mimic such a modulation.

For the two detectors planned for SABRE, annual weather-based environmental factors should be out-of-phase between the two sites- but a putative dark-matter-induced modulation should have the same phase for both sites.

The detection of such an in-phase modulation, consistent between both sites, would strengthen the support for candidate dark-matter particles as has been suggested by the DAMA/LIBRA results.

The locations of SABRE North (Italy, LNGS) and SABRE South (Australia, SUPL)

The locations of SABRE North (Italy, LNGS) and SABRE South (Australia, SUPL)