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DAMA/LIBRA

Particle detector experiment

Particle detector experiment

The DAMA/LIBRA experiment |display-authors=etal is a particle detector experiment designed to detect dark matter using the direct detection approach, by using a matrix of NaI(Tl) scintillation detectors to detect dark matter particles in the galactic halo. The experiment aims to find an annual modulation of the number of detection events, caused by the variation of the velocity of the detector relative to the dark matter halo as the Earth orbits the Sun. It is located underground at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy.

It is a follow-on to the DAMA/NaI experiment which observed an annual modulation signature over 7 annual cycles (1995-2002). The experiment was first proposed by Dr. Pierluigi Belli, who is now the research director of the Italian National Institute of Nuclear Physics.

While DAMA/LIBRA has published exciting results, the validity of those results has been widely disputed; they have not made their data or practices publicly available, and their methods of background noise reduction is such that it may actually account for a large part of their proposed signal annual modulation. Two other studies, attempting to replicate the DAMA/LIBRA experiment (adhering to current publication and data availability practices) using the same method - COSINE-100 and ANAIS-112 - have shown no evidence of annual modulation.

In 2020, a possible explanation of the reported modulation was pointed out as originating from the data analysis procedure. A yearly subtraction of the constant component can give rise to a sawtooth residual in the presence of a slower time dependence.

Detector

The detector is made of 25 highly radiopure scintillating thallium-doped sodium iodide (NaI(Tl)) crystals placed in a 5 by 5 matrix. Each crystal is coupled to two low background photomultipliers. The detectors are placed inside a sealed copper box flushed with highly pure nitrogen; to reduce the natural environmental background the copper box is surrounded by a low background multi-ton shield. In addition, 1 m of concrete, made from the Gran Sasso rock material, almost fully surrounds this passive shield. The installation has a 3-level sealing system which prevents environmental air reaching the detectors. The whole installation is air-conditioned and several operative parameters are continuously monitored and recorded.

DAMA/LIBRA was upgraded in 2008 and in 2010. |display-authors=etal thanks to the lowering of the energy threshold. The DAMA/LIBRA-phase 2 is in data taking as of 2022.

Operation and results

DAMA/LIBRA phase 1 data collection started in September 2003. The DAMA/LIBRA released data correspond to 7 annual cycles.{{cite journal |display-authors=etal

As previously done for DAMA/NaI, careful investigations on absence of any significant systematics or side reaction in DAMA/LIBRA have been quantitatively carried out.{{cite journal |display-authors=etal

The obtained model independent evidence is compatible with a wide set of scenarios regarding the nature of the dark matter candidate and related astrophysical and particle physics. |display-authors=etal |display-authors=etal

As of 2021, the DAMA/LIBRA experiment is continuing.

Failure to replicate

The results can be compared with the CoGeNT signal{{cite journal |display-authors=etal |display-authors=etal |display-authors=etal |display-authors=etal |display-authors=etal

The COSINE-100 collaboration has been working in Korea towards confirming or refuting the DAMA-signal. They are using similar experimental setup to DAMA (NaI(Tl)-crystals). They published their results in December 2018 in the journal Nature; their result rules out spin-independent WIMP–nucleon interactions as the cause of the annual modulation observed by the DAMA collaboration.

In May 2021, the ANAIS particle detector failed to replicate the results of the DAMA experiments after 3 years of data collection and in November new results from COSINE-100 experiment after 1.7 years of data collection also failed to replicate the signal of DAMA.

A possible explanation of the reported modulation was pointed out as originating from the data analysis procedure. A yearly subtraction of the constant component can give rise to a sawtooth residual in the presence of a slower time dependence,{{cite journal |display-authors=etal

SABRE

The obvious criticism of the seasonal variation of events recorded in the DAMA/LIBRA experiment is that it is in fact due to some purely seasonal effect unconnected with WIMPs. Although the deep underground location minimizes temperature swings and other direct sunlight effects, there are annual humidity fluctuations and other non-obvious effects. At the moment, all these criticisms are taken into account by DAMA collaboration in analysis of the experimental data and they have been excluded, as discussed in published results. A repetition of this experiment in the Southern Hemisphere with the variation in phase with DAMA/LIBRA would discount this objection; if on the other hand variation was detected in the Southern Hemisphere that was 6 months out of phase with DAMA/LIBRA, then the seasonal variation objection would be upheld.

Improved versions of DAMA/LIBRA, named SABRE (Sodium-iodide with Active Background REjection) were planned for construction in two places. One at LNGS, and the other in Australia at the Stawell Underground Physics Laboratory (SUPL), a laboratory being constructed 1025 m below the surface in a gold mine in Stawell, Victoria. First results were expected in 2017. The construction of the Stawell Underground Physics Laboratory (SUPL) was halted by the shutdown of its host mine in 2016. Construction restarted around one year later and as of October 2019 was proceeding.

The host laboratory, SUPL, was opened in August 2022. The SABRE experiment is planned to be brought underground to SUPL during the last months of 2022 and data collection is planned to start in 2023.

In October 2023, the first piece of equipment, the muon veto, was installed. In January 2024, the main muon system was installed. In April 2024, the SABRE collaboration published an executive summary providing in-depth details of the detector's design.

References

References

  1. [http://www.sciencenews.org/article/dark-matter-claim-dama-cosine/amp ''A controversial sighting of dark matter is looking even shakier'' 2018]
  2. [https://www.nature.com/articles/d41586-019-00865-9 ''Mystery of dark-matter signal deepens with replication attempts'' March 2019]
  3. [https://arxiv.org/abs/2103.01175 ''Annual modulation results from three-year exposure of ANAIS-112'' Amare 2021]
  4. [https://www.nature.com/articles/s41586-018-0739-1 ''An experiment to search for dark-matter interactions using sodium iodide detectors'' COSINE-100 2018]
  5. (2021). "Further results from DAMA/LIBRA-phase2 and perspectives". Nuclear Physics and Atomic Energy.
  6. (2018). "An experiment to search for dark-matter interactions using sodium iodide detectors". Nature.
  7. J. Amaré. (2021). "Annual modulation results from three-year exposure of ANAIS-112". Physical Review D.
  8. (2021-11-12). "Strong constraints from COSINE-100 on the DAMA dark matter results using the same sodium iodide target". Science Advances.
  9. "Is the end in sight for famous dark matter claim?".
  10. (2020-04-22). "Annual modulations from secular variations: not relaxing DAMA?". Journal of Cosmology and Astroparticle Physics.
  11. (2023). "An induced annual modulation signature in COSINE-100 data by DAMA/LIBRA's analysis method". Scientific Reports.
  12. Roberts, Glenn Jr.. (23 October 2014). "Australia's first dark matter experiment". Symmetry Magazine.
  13. (26 November 2015). "Dark Matter: A Southern Hemisphere Perspective".
  14. "Home".
  15. "News Archive".
  16. Barberio, E.. (2025-04-01). "The SABRE South technical design report executive summary". Journal of Instrumentation.
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