A few days ago the results of the SuperCDMS (Cryiogenic Dark Matter Search) Collaboration were presented concerning the analysis of the data obtained through silicon detectors during the CDMSII experiment for the search for dark matter. Some events are new clues to the discovery of this elusive type of matter.
The CDMS experiments started at Stanford University with the CDMSI carried out in a tunnel under the campus. The big breakthrough came with the CDMSII, installed in an old iron mine in Soudan, Minnesota. This experiment was upgraded into the SuperCDMS, with bigger and better detectors.
The detectors of these experiments are cooled to temperature very close to absolute zero and this allows them to detect the heat produced when a particle hits one of their crystals. From the measurements of the ionization and the characteristics of the collision it’s possible to understand what kind of particle caused it.
The WIMP (Weakly Interacting Massive Particle) particles are the hypothetical dark matter particles, so called because in theory they interact very weakly with ordinary matter. For this reason the possibility of detecting that type of interaction is very rare.
In 2010, two anomalous events were recorded during the CDMSII experiment but after the analysis the scientists concluded that they were indistinguishable from background noise, meaning from the normal interactions of ordinary matter particles. Now scientists have reported three new anomalous events and this time the particles that caused them could be of dark matter.
In statistical language, the confidence level is 3 sigma. It’s a good level but still far from a probability high enough to talk about an actual discovery. To be clear, the experiments that searched for the Higgs boson gave a confidence level of 5 sigma, which is much higher in statistical terms, yet the research continues and there are still doubts about the nature of this particle.
The results of the CDMSII experiment still seem more promising than those of the AMS announced in early April but for now they constitute only a small step forward in the search for dark matter. One of the points to be clarified is the fact that the mass of the particle detected would be approximately 8.6 gigaelectronvolts, much lower than the physicists expected.
There are also other experiments around the world that have the purpose of discovering dark matter particles so we just have to wait for new results to see if any of them will provide more interesting and above all more conclusive results.
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