The DAMA/NaI experiment [1] was designed to detect dark matter using the direct detection technique. It was located at the Gran Sasso National Laboratory 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 rotation 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 [2]. The case of spin dependent interactions is studied in [3,4,5]. Inelastic dark matter [6], mirror matter [7] and self-interacting dark matter [8] can also explain the DAMA results.
External links
[1] R. Bernabei et al. Dark Matter search, Riv. Nuovo Cim. 26N1, 1-73 (2003) preprint.
[2] G. Gelmini and P. Gondolo, DAMA Dark Matter Detection Compatible with Other Searches preprint
[3]P. Ullio, M. Kamionkowski and P. Vogel, Spin-Dependent WIMPs in DAMA?, JHEP 0107, 044 (2001) preprint.
[4] F. Giuliani, Model-Independent Assessment of Current Direct Searches for Spin-Dependent Dark Matter, Phys. Rev. Lett. 93, 161301 (2004) preprint.
[5] C. Savage, P. Gondolo and K. Freese, Can WIMP Spin Dependent Couplings explain DAMA data, in light of Null Results from Other Experiments?, Phys. Rev. D 70, 123513 (2004) preprint
[6] D. T. Smith and N. Weiner, The Status of Inelastic Dark Matter, preprint.
[7] R. Foot, Reconciling the positive DAMA annual modulation signal with the negative results of the CDMS II experiment, Mod. Phys. Lett. A 19, 1841 (2004) preprint.
[8] S. Mitra, Has Dama Detected Self-Interacting Dark Matter?, preprint.
