DAMA/LIBRA

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The DAMA/LIBRA experiment[1] is a particle detector experiment designed to detect dark matter using the direct detection approach, by using a scintillation detector to search for Weakly Interacting Massive Particles (WIMPs) in the galactic halo. The experiment aims to find an annual variation 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 at the Laboratori Nazionali del Gran Sasso in Italy.

It is a follow-on to the DAMA/NaI experiment which observed an annual modulation signature over 7 annual cycles (1995-2002).

Detector[edit]

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.[2] In particular, the upgrade in 2010 allows an increase of the set-up’s sensitivity, the lowering of the energy threshold, and several other kinds of investigations.

Operation and results[edit]

Data collection started in Sept 2003.[3] The DAMA/LIBRA data released so far correspond to 4[3] and 7 annual cycles.[4] Considering these data together with those by DAMA/NaI, a total exposure (1.17 ton x yr) has been collected over 13 annual cycles.[4] This experiment has further confirmed the presence of model-independent evidence with high statistical significance on the basis of the dark matter signature. DAMA/LIBRA is sensitive to 2 keV to 20 keV and annual modulation is seen in the 2-6 keV range.[3]

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.[3][4][5]

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.[6][7]

Final phase 1 results were published in 2013, confirming an annual modulation.[8]

Interpretation and comparisons[edit]

The results can be compared with the CoGeNT signal[9][10][11][12] and other experiment limits to evaluate interpretations as WIMPs,[13] neutralino,[14] and other models.

A mechanism explaining the results of this experiment by muons and neutrinos was proposed in 2014.[15] Others claim muons are not enough to produce the modulation.[16]

SABRE[edit]

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 minimized temperature swings and other direct sunlight effects, there are annual humidity fluctuations and other non-obvious effects. At moment, all these criticisms are taken in account by DAMA collaboration in analysis of the experimental data and they have been excluded, as discussed in literatures. 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.

An improved version of DAMA/LIBRA, named SABRE (Sodium-iodide with Active Background REjection) is under construction in two copies. One will be installed at LNGS, and the other will be installed in Australia at the Stawell Underground Physics Laboratory,[17] a laboratory being constructed 1025 m below the surface in a gold mine in Stawell, Victoria. First results are expected in 2017.[18]

References[edit]

  1. ^ R. Bernabei; et al. (2008). "The DAMA/LIBRA apparatus". Nuclear Instruments and Methods in Physics Research A. 592 (3): 297. Bibcode:2008NIMPA.592..297B. arXiv:0804.2738Freely accessible. doi:10.1016/j.nima.2008.04.082. 
  2. ^ R. Bernabei; et al. (2012). "Performances of the new high quantum efficiency PMTs in DAMA/LIBRA". European Physical Journal C. 7 (3): 03009. Bibcode:2012JInst...7.3009B. arXiv:1002.1028Freely accessible. doi:10.1088/1748-0221/7/03/P03009. 
  3. ^ a b c d R. Bernabei; et al. (2008). "First results from DAMA/LIBRA and the combined results with DAMA/NaI". European Physical Journal C. 56 (3): 333. Bibcode:2008EPJC...56..333B. arXiv:0804.2741Freely accessible. doi:10.1140/epjc/s10052-008-0662-y. 
  4. ^ a b c R. Bernabei; et al. (2010). "New results from DAMA/LIBRA". European Physical Journal C. 67 (1): 39. Bibcode:2010EPJC...67...39B. arXiv:1002.1028Freely accessible. doi:10.1140/epjc/s10052-010-1303-9. 
  5. ^ R. Bernabei; et al. (2012). "No role for muons in the DAMA annual modulation results". European Physical Journal C. 72 (7): 2064. Bibcode:2012EPJC...72.2064B. arXiv:1202.4179Freely accessible. doi:10.1140/epjc/s10052-012-2064-4. 
  6. ^ A. Bottino; et al. (2012). "Phenomenology of light neutralinos in view of recent results at the CERN Large Hadron Collider". Physical Review D. 85 (9): 095013. Bibcode:2012PhRvD..85i5013B. arXiv:1112.5666Freely accessible. doi:10.1103/PhysRevD.85.095013. 
  7. ^ M. R. Buckley; et al. (2011). "Particle Physics Implications for CoGeNT, DAMA, and Fermi". Physics Letters B. 702 (4): 216. Bibcode:2011PhLB..702..216B. arXiv:1011.1499Freely accessible. doi:10.1016/j.physletb.2011.06.090. 
  8. ^ R. Bernabei; et al. (2013). "Final model independent result of DAMA/LIBRA-phase1". European Physical Journal C. 73 (12): 2648. Bibcode:2013EPJC...73.2648B. arXiv:1308.5109Freely accessible. doi:10.1140/epjc/s10052-013-2648-7. 
  9. ^ C.E. Aalseth; et al. (2011). "Results from a Search for Light-Mass Dark Matter with a P-type Point Contact Germanium Detector". Physical Review Letters. 106 (13): 131301. Bibcode:2011PhRvL.106m1301A. PMID 21517370. arXiv:1002.4703Freely accessible. doi:10.1103/PhysRevLett.106.131301. 
  10. ^ C.E. Aalseth; et al. (2011). "Search for an Annual Modulation in a P-type Point Contact Germanium Dark Matter Detector". Physical Review Letters. 107 (14): 141301. Bibcode:2011PhRvL.107n1301A. PMID 22107183. arXiv:1106.0650Freely accessible. doi:10.1103/PhysRevLett.107.141301. 
  11. ^ M.T. Frandsen; et al. (2011). "On the DAMA and CoGeNT Modulations". Physical Review D. 84 (4): 041301. Bibcode:2011PhRvD..84d1301F. arXiv:1105.3734Freely accessible. doi:10.1103/PhysRevD.84.041301. 
  12. ^ Dan Hooper, Chris Kelso (2011). "Implications of CoGeNT's New Results For Dark Matter". Physical Review D. 84 (8): 083001. Bibcode:2011PhRvD..84h3001H. arXiv:1106.1066Freely accessible. doi:10.1103/PhysRevD.84.083001. 
  13. ^ A. Liam Fitzpatrick; et al. (2010). "Implications of CoGeNT and DAMA for Light WIMP Dark Matter". Physical Review D. 81 (11): 115005. Bibcode:2010PhRvD..81k5005F. arXiv:1003.0014Freely accessible. doi:10.1103/PhysRevD.81.115005. 
  14. ^ A.V. Belikov; et al. (2011). "CoGeNT, DAMA, and Light Neutralino Dark Matter". Physics Letters B. 705 (1–2): 82. Bibcode:2011PhLB..705...82B. arXiv:1009.0549Freely accessible. doi:10.1016/j.physletb.2011.09.081. 
  15. ^ J.H. Davis (2014). "Fitting the Annual Modulation in DAMA with Neutrons from Muons and Neutrinos". Physical Review Letters. 113 (8): 081302. Bibcode:2014PhRvL.113h1302D. arXiv:1407.1052Freely accessible. doi:10.1103/PhysRevLett.113.081302. 
  16. ^ Klinger, J.; Kudryavtsev, V. A. (2015). "Muon-induced neutrons do not explain the DAMA data". Physical Review Letters. 114 (15): 151301. Bibcode:2015PhRvL.114o1301K. PMID 25933303. arXiv:1503.07225Freely accessible. doi:10.1103/PhysRevLett.114.151301. 
  17. ^ http://www.symmetrymagazine.org/article/october-2014/australias-first-dark-matter-experiment
  18. ^ https://royalsocietyvictoria.org.au/events/the-hunt-for-dark-matter/

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