.
DAMA/LIBRA
The DAMA/LIBRA experiment[1] is a particle detector experiment designed to detect dark matter using the direct detection approach, by using a scintilation 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.
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.[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
The DAMA/LIBRA data released so far correspond to 7 annual cycles.[3][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. This experiment has further confirmed the presence of model-independent evidence with high statistical significance on the basis of the dark matter signature. 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 results can be compared with the CoGent signal[6][7][8] [9] and other experiment limits to evaluate interpretations as WIMPs,[10] neutralino,[11] and other models. 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.[12] [13]
Final phase 1 results were published in 2013, confirming an annual modulation.[14]
A mechanism explaining the results of this experiment by muons and neutrinos has been recently put forward.[15] Others claim muons are not enough to produce the modulation.[16]
References
R. Bernabei; et al. (2008). "The DAMA/LIBRA apparatus". Nuclear Instruments and Methods in Physics Research A 592 (3): 297. arXiv:0804.2738. Bibcode:2008NIMPA.592..297B. doi:10.1016/j.nima.2008.04.082.
R. Bernabei; et al. (2012). "Performances of the new high quantum efficiency PMTs in DAMA/LIBRA". European Physical Journal C 7: 03009. arXiv:1002.1028. Bibcode:2012JInst...7.3009B. doi:10.1088/1748-0221/7/03/P03009.
R. Bernabei; et al. (2008). "First results from DAMA/LIBRA and the combined results with DAMA/NaI". European Physical Journal C 56: 333. arXiv:0804.2741. doi:10.1140/epjc/s10052-008-0662-y.
R. Bernabei; et al. (2010). "New results from DAMA/LIBRA". European Physical Journal C 67: 39. arXiv:1002.1028. Bibcode:2010EPJC...67...39B. doi:10.1140/epjc/s10052-010-1303-9.
R. Bernabei; et al. (2012). "No role for muons in the DAMA annual modulation results". arXiv:1202.4179. Bibcode:2012EPJC...72.2064B. doi:10.1140/epjc/s10052-012-2064-4.
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: 131301. arXiv:1002.4703. Bibcode:2011PhRvL.106m1301A. doi:10.1103/PhysRevLett.106.131301.
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: 141301. arXiv:1106.0650. Bibcode:2011PhRvL.107n1301A. doi:10.1103/PhysRevLett.107.141301.
M.T. Frandsen; et al. (2011). "On the DAMA and CoGeNT Modulations". Physical Review D 84: 041301. arXiv:1105.3734. Bibcode:2011PhRvD..84d1301F. doi:10.1103/PhysRevD.84.041301.
Dan Hooper, Chris Kelso (2011). "Implications of CoGeNT's New Results For Dark Matter". PhysRevD. arXiv:1106.1066. Bibcode:2011PhRvD..84h3001H. doi:10.1103/PhysRevD.84.083001.
A. Liam Fitzpatrick; et al. (2010). "Implications of CoGeNT and DAMA for Light WIMP Dark Matter". arXiv:1003.0014. Bibcode:2010PhRvD..81k5005F. doi:10.1103/PhysRevD.81.115005.
A.V. Belikov; et al. (2011). "CoGeNT, DAMA, and Light Neutralino Dark Matter". arXiv:1009.0549. Bibcode:2011PhLB..705...82B. doi:10.1016/j.physletb.2011.09.081.
A. Bottino; et al. (2012). "Phenomenology of light neutralinos in view of recent results at the CERN Large Hadron Collider". Physical Review D 85: 095013. arXiv:1112.5666. Bibcode:2012PhRvD..85i5013B. doi:10.1103/PhysRevD.85.095013.
M. R. Buckley; et al. (2011). "Particle Physics Implications for CoGeNT, DAMA, and Fermi". Physics Letters B 702: 216. arXiv:1011.1499. Bibcode:2011PhLB..702..216B. doi:10.1016/j.physletb.2011.06.090.
"Final model independent result of DAMA/LIBRA-phase1". Eur. Phys. J. C 73 (2013) 2648. 2013.
Jonathan H. Davis (2014). "Fitting the Annual Modulation in DAMA with Neutrons from Muons and Neutrinos". Physical Review Letters 113: 081302. arXiv:1407.1052. Bibcode:2014PhRvL.113h1302D. doi:10.1103/PhysRevLett.113.081302.
"Muon-induced neutrons do not explain the DAMA data". PRL. 24 Mar 2015.
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