The Super-CDMS dark-matter search has released two days ago the results from the analysis of nine months of data taking. The experiment has excellent sensitivity to weak interacting massive particles producing inelastic scattering with the Germanium in the detector.
The detector is composed of fifteen cylindrical 0.6 kg crystals stacked in groups of three, equipped with ionization and phonon detectors that are capable of measuring the energy of the signals. From that the recoil energy can be derived, and a rough estimate of WIMP candidates mass. The towers are kept at close to absolute zero temperature in the Soudan mine, where backgrounds from cosmic rays and other sources are very small.
The search revealed a total of 11 phonon candidates, when 6.1+1.1-0.8 were expected from the considered background sources. This is only a mild excess, that happens by chance more than once in twenty trials (p=0.065). However, one of the seven considered detectors saw 3 energetic events, while its background prediction was of only 0.13+0.06-0.04 events. According to the CDMS paper this corresponds to a 4x10^-4 probability (I calculate 0.00054). That's a 3.4 standard deviations effect, but do not get excited...
In fact, the paper is careful to point out that the excess (three high-energy events) concentrates in the only detector which "has a ionization guard electrode shorted to ground". They suggest that their background prediction was therefore possibly incorrect.
The graph above shows the detected energy of the 11 candidates, compared with a model of possible signals from WIMPS of masses between 5 and 15 GeV. The three events detected by the "shorted" detector are in yellow.
The interim conclusions of the search (which is ongoing) are that a number of tentative signals observed by other experiments are strongly disfavoured; these include CoGeNT and CDMS II.
For more information please see the preprint.
- PHYSICAL SCIENCES
- EARTH SCIENCES
- LIFE SCIENCES
- SOCIAL SCIENCES
Subscribe to the newsletter
Stay in touch with the scientific world!
Know Science And Want To Write?
- Not Just Vitamin D - The Radiation In Sunshine May Be Healthy
- Ignorance Of Math And Physics Is No Excuse
- War On Doping And The Hypocritical Treatment Of Lance Armstrong
- Quantum Cryptography Core Question At The Heart Of Quantum Information Theory Answered?!?
- Mars Lost An Ocean’s Worth Of Water
- Science Debunks Fad Ideas About Autism, But That Doesn't Dissuade Believers
- GMO Soybean Oil Is Healthier Than Organic Or Conventional
- "So many people in Australia nowadays are afraid of any direct contact with the Sun because they..."
- "Nope You can treat for the mites. It is done effectively every day. And the poorly funded research..."
- "And you would not equate McCarthy to Hitler or Stalin? ..."
- "Because anti-communism is indeed on the same shelf as racism and greed. Just another ideology of..."
- "I think I have to agree with you here. I think he changed the culture of doping not doping itself..."
- BPA harms dental enamel in young animals, mimicking human tooth defect
- People with anorexia, body dysmorphic disorder share brain anomalies
- Feeling sleepy? Might be the melatonin
- Chromosomal rearrangement is the key to progress against aggressive infant leukemia
- Infant growth affected by exposure to environmental pollutants