An experiment on dark matter in South Korea could soon confirm or deny an exceptional piece of evidence on dark matter.
The observations on the universe reveal that it consists mainly of things that scientists do not understand. Normal matter seems to constitute less than 5% of the universe, dark energy around 68%, and the rest is dark matter, a mysterious material that has only been detected by its gravity. Recently, an experiment called DAMA / LIBRA in Italy claimed to have identified evidence for this dark matter. A new experiment, COSINE-100, has just published its results, but has not identified the signal of DAMA / LIBRA.
"What we can say is that the spin-independent dark matter," which refers to a simpler theoretical model of dark matter, "is not causing the DAMA signal," said Reina Maruyama, associate professor of physics at Yale, told Gizmodo.
The physicists of DAMA / LIBRA in Italy reported an annual signal in the sodium iodide crystals detectors of the experiment, which would emit a small beep of light in the event that a hypothetical dark matter particle passed and gave a boost. Researchers interpret this as a variable amount of dark matter, changing according to the orientation of the Earth relative to the rest of the galaxy. COSINE-100 is another experiment that contains 106 kilograms of sodium iodide crystals, located in the underground laboratory of Yangyang in South Korea.
The scientists used COSINE-100 to take data from October 20, 2016 and December 19, 2016, and found no evidence of the dark matter that DAMA / LIBRA has identified. Although other experiments failed to detect the signal, COSINE-100 is the first product from the sodium iodide itself, so its failure to confirm the DAMA / LIBRA findings is an even more significant sign that the Italian experiment might not be actually perceivable dark matter.
The spokesperson for DAMA / LIBRA, Rita Bernabei of the University of Rome Tor Vergata, told Gizmodo that the results of COSINE-100 do not change anything. He did not think that COSINE-100 was sensitive to the transitions of dark matter that his scientists claimed it was, and that the signal could still appear if "a more correct, realistic and reliable" model of potential background noise sources was used. But Dan Hooper, a physician at the University of Chicago, told Science News that the results of COSINE-100 were "another nail in the coffin".
This is only the first phase of the work in the South Korean experiment, Maruyama told Gizmodo. The team has only searched for background noise and still needs to look for the annual modulation as the annual signal seen by DAMA / LIBRA. Other sodium iodide detectors will similarly attempt to verify previous claims, as reported.
But if a second experiment made from the same material can not verify the statements made by the former, it is a sign that the strange DAMA / LIBRA signal detected may not be dark matter after all.