DAMA/NaI

The DAMA/NaI experiment was designed to detect dark matter using the direct detection technique. It was located at the Laboratori Nazionali del Gran Sasso in Italy and collected data during the period 1996-2002. Its successor is the DAMA/LIBRA experiment, which uses very similar detector technology but has a larger target mass of 250 kg.

The DAMA/NaI set up consisted of 9 scintillating thallium-doped sodium iodide (NaI) crystals of 9.7 kg each. Electrons and nuclei recoiling after a collision cause emissions of photons that are detected using photomultiplier tubes. A detected recoil can be caused by dark matter particles or by the background (thermal neutrons, radioactivity or cosmic radiation). The revolution of the Earth around the Sun causes an annual modulation of the dark matter flux. This should give rise to an annual modulation in the detected recoils and thus provides a simple way to extract a dark matter signal from the background.

The DAMA/NaI experiment has used this technique and is the only one to have reported a positive signal. The results of this experiment are controversial because other searches have not detected nuclear recoils due to dark matter interactions. All these other searches use sophisticated background elimination techniques instead of the annual modulation technique.

For weakly interacting massive particles (WIMP) interacting with nuclei through spin independent interactions, the available parameter space consistent with DAMA and all other experiments is very limited. The case of spin dependent interactions is studied in three papers. Inelastic dark matter, mirror matter, self-interacting dark matter, scalar and pseudoscalar dark matter and fourth generation neutrinos have also been proposed as possible explanations for the DAMA signal.

See also

• PVLAS

References