Yale scientists are part of a new international experiment that challenges previous claims about the detection of dark non-luminous matter.
Astrophysical evidence suggests that the universe contains a large amount of dark, non-luminous matter, although no definite sign has been observed despite the joint efforts of many experimental groups. One exception to this is the long-debated claim by DArk MAtter (DAMA), which reported positive observations of dark matter on its sodium iodide detector array.
The new COSINE-100 experiment, based on an underground dark matter detector at the Yangyang Underground Laboratory in South Korea, began exploring DAMA's claim. It is the first experience sensitive enough to test DAMA and use the same target material as sodium iodide.
COSINE-100 records data since 2016 and now presents initial results that challenge DAMA's findings. These findings are published online this week in the journal Nature.
"For the first time in 20 years, we have a chance to solve the DAMA puzzle," said Yale physics professor Reina Maruyama, who is co-spokeswoman for COSINE-100 and co-author of the new study.
The first phase of the COSINE-100's work looks for dark matter, looking for an excess signal on the background expected in the detector, with the right energy and characteristics. In this initial study, the researchers did not find any excess signal in their data, placing the annual modulation signal of the DAMA at odds with the results of other experiments. The COSINE-100 scientists noted that it will take several years of data to fully confirm or refute the results of DAMA.
The COSINE-100 experiment uses eight low-bottom, doped doped sodium iodide crystals arranged in a 4 by 2 matrix, resulting in a total target mass of 106 kg. Each crystal is coupled by two photographic sensors to measure the amount of energy deposited in the crystal.
The crystalline sets of sodium iodide are immersed in 2,200 L of light emitting liquid, which allows the identification and subsequent reduction of radioactive backgrounds observed by the crystals. The detector is contained in a nested arrangement of copper, lead and plastic components to reduce the background contribution of external radiation as well as cosmic ray muons.
The COSINE-100 collaboration includes 50 scientists from the USA, South Korea, the United Kingdom, Brazil and Indonesia. The Yangyang Underground Laboratory, where the experiment is based, is operated by the Center for Underground Physics of the Institute of Basic Science (IBS) in South Korea.
"The initial results sculpt a reasonable portion of the possible dark matter search region drawn by the DAMA sign. In other words, there is little room for this affirmation to be of dark matter interaction unless the dark matter model is significantly modified, said Hyun Su Lee, the other co-spokesperson for COSINE-100, and associate director of the IBS Underground Physics Center.
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