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Posts: 131433
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CDMS II experiment
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Title: Dark Matter Search Results Using the Silicon Detectors of CDMS II
Authors: CDMS Collaboration: R. Agnese, Z. Ahmed, A.J. Anderson, S. Arrenberg, D. Balakishiyeva, R. Basu Thakur, D.A. Bauer, J. Billard, A. Borgland, D. Brandt, P.L. Brink, T. Bruch, R. Bunker, B. Cabrera, D.O. Caldwell, D.G. Cerdeno, H. Chagani, J. Cooley, B. Cornell, C.H. Crewdson, P. Cushman, M. Daal, F. Dejongh, E. Do Couto E Silva, T. Doughty, L. Esteban, S. Fallows, E. Figueroa-Feliciano, J. Filippini, J. Fox, M. Fritts, G.L. Godfrey, S.R. Golwala, J. Hall, R.H. Harris, S.A. Hertel, T. Hofer, D. Holmgren, L. Hsu, M.E. Huber, A. Jastram, O. Kamaev, B. Kara, M.H. Kelsey, A. Kennedy, P. Kim, M. Kiveni, K. Koch, M. Kos, S.W. Leman, B. Loer, E. Lopez Asamar, R. Mahapatra, V. Mandic, C. Martinez, K.A. McCarthy, N. Mirabolfathi, R.A. Moffatt, D.C. Moore, P. Nadeau, R.H. Nelson, K. Page, R. Partridge, et al. (27 additional authors not shown)

We report results of a search for Weakly Interacting Massive Particles (WIMPs) with the silicon (Si) detectors of the CDMS II experiment. A blind analysis of data from eight Si detectors, with a total raw exposure of 140.2 kg-days, revealed three WIMP-candidate events with a final surface-event background estimate of 0.41 (-0.08 +0.20)(stat.) (-0.24 +0.28) (syst.). Other known backgrounds from neutrons and 206Pb are limited to < 0.13 and < 0.08 events at the 90% confidence level, respectively. These data place a 90% upper confidence limit on the WIMP-nucleon cross section of 2.4E-41 cm at a WIMP mass of 10 GeV/c. Simulations indicate a 5.4% probability that a statistical fluctuation of the known backgrounds would produce three or more events in the signal region. A profile likelihood ratio test that includes the measured recoil energies of the three events gives a 0.19% probability for the known-background-only hypothesis when tested against the alternative WIMP+background hypothesis. The highest likelihood was found for a WIMP mass of 8.6 GeV/c^2 and WIMP-nucleon cross section of 1.9E-41 cm.

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Posts: 131433
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RE: CDMS Experiment
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Dark-matter experiment CDMS sees three tentative clues

Researchers have revealed the first potential hints of the elusive material called dark matter at an underground laboratory in the US.
Though it is believed to make up a quarter of our Universe, dark matter - true to its name - has never been seen.
Scientists at the American Physical Society meeting showed three promising clues of it from the CDMS experiment.

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Title: A Maximum Likelihood Analysis of Low-Energy CDMS Data
Authors: J. I. Collar, N. E. Fields

An unbinned maximum likelihood analysis of CDMS low-energy data reveals a strong preference (5.7 sigma C.L.) for a model containing an exponential excess of events in the nuclear recoil band, when compared to the null hypothesis. We comment on the possible origin of such an excess, establishing a comparison with anomalies in other dark matter experiments. A recent annual modulation search in CDMS data is shown to be insufficiently sensitive to test a dark matter origin for this excess.

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Title: On the DAMA and CoGeNT Modulations
Authors: Mads T. Frandsen, Felix Kahlhoefer, John March-Russell, Christopher McCabe, Matthew McCullough, Kai Schmidt-Hoberg

DAMA observes an annual modulation in their event rate, as might be expected from dark matter scatterings, while CoGeNT has reported evidence for a similar modulation. The simplest interpretation of these findings in terms of dark matter-nucleus scatterings is excluded by other direct detection experiments. We consider the robustness of these exclusions with respect to assumptions regarding the scattering and find that isospin-violating inelastic dark matter helps alleviate this tension and allows marginal compatibility between experiments. Isospin-violation can significantly weaken the XENON constraints, while inelasticity enhances the annual modulation fraction of the signal, bringing the CoGeNT and CDMS results into better agreement.

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Posts: 131433
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Soudan Underground Laboratory
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Fire slows dark matter search

Neutrino and dark matter experiments in a former iron mine in Minnesota have escaped serious harm from a fire, but damage to laboratory infrastructure means it will take at least a few more weeks to get them running again.
Sparks created during maintenance work on the Soudan Underground Laboratory started a fire on 17 March. Firefighters quickly put it out by injecting foam and water into the mine shaft, where the fire was located. But it was not immediately clear how much damage had been done to the experiments.

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Posts: 131433
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Cryogenic Dark Matter Search II Experiment
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An underground experiment designed to search for signals from dark matter could relocate to an even deeper site.
Cosmic rays striking the Earth could completely mask the rare dark matter events sought by the experiment.
Team members want to cut out as much of this cosmic ray interference as possible, even if it means moving the experiment 2km below ground.

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Posts: 131433
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RE: CDMS Experiment
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Dark matter claims thrown into doubt by new data

Previous claims that dark matter had been detected are being called into doubt now that a powerful new experiment has failed to see any of the elusive particles.
For years, scientists running the DAMA experiment beneath a mountain in Italy have reported a seasonal variation in the number of light flashes seen in their sodium iodide target. They claim the variability is due to changes in the speed of dark matter particles streaming through the laboratory as a result of Earth's orbital motion around the sun.
In December 2009, scientists also reported two possible dark matter particle impacts in an experiment called the Cryogenic Dark Matter Search II.

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Researchers in the US say they have detected two signals which could possibly indicate the presence of particles of dark matter.
But the study in Science journal reports the statistical likelihood of a detection of dark matter as 23%.
Deep underground in a lab in Minnesota experiments to detect WIMPS, or Weakly Interacting Massive Particles have been going on since 2003.

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Posts: 131433
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Dark matter
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A decades-long search for the invisible "dark matter" that gives shape to galaxies and forms the bulk of the Universe's mass may be over.
If confirmed, the finding will rank as a milestone in physics and take a big step toward completing the picture of the matter that composes our Universe.

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Posts: 131433
Date:
RE: CDMS Experiment
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US scientists have reported the detection of signals that could indicate the presence of dark matter.
A team announced on Thursday detecting two events with characteristics "consistent with" what physicists believe make up the elusive matter.

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