The Korea Invisible Mass Search (KIMS), is a South Korean experiment, led by Sun Kee Kim, searching for

weakly interacting massive particles Weakly interacting massive particles (WIMPs) are hypothetical particles that are one of the proposed candidates for dark matter. There exists no formal definition of a WIMP, but broadly, a WIMP is a new elementary particle which interacts via gra ...

(WIMPs), one of the candidates for

dark matter Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not a ...

. The experiments use CsI( Tl) crystals at Yangyang Underground Laboratory (Y2L), in tunnels from a preexisting underground power plant. KIMS is supported by the Creative Research Initiative program of the Korea Science and Engineering Foundation. It is the first physics experiment located, and largely built, in Korea. Other research topics include detector development for a

neutrino A neutrino ( ; denoted by the Greek letter ) is a fermion (an elementary particle with spin of ) that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass ...

less double beta decay search and the creation of an extreme low temperature diamond

calorimeter A calorimeter is an object used for calorimetry, or the process of measuring the heat of chemical reactions or physical changes as well as heat capacity. Differential scanning calorimeters, isothermal micro calorimeters, titration calorimete ...

History

The KIMS experiment was funded in 2000 to search for WIMP dark matter. To avoid the cost of creating a new tunnel for testing, the Yangyang Pumped Storage Power Plant belonging to Korea Middleland Power Co. in

Yangyang Yangyang County (''Yangyang-gun'') is in Gangwon Province, South Korea. The county is located in the northeast of the country in Gangwon-do. Its population is about 31,000 (2004). The Yangyang area is well known for its pine mushrooms (''son ...

, Korea was used. Construction was completed in 2003. The CsI(Tl) scintillating crystal used has a high light yield and is affordable for large mass. After a substantial effort for the initial setup and crystal development, KIMS began recording data in 2004 with one full-size 6 kg crystal. A 4 crystal setup was run in 2005-2006 to optimize the WIMP search. In 2008, the 12 crystal array with 103.4 kg mass was completed and ran until December 2012 for a detector upgrade replacing the PMTs.

Results

The first WIMP cross section search was published in 2006 using the one crystal data. New limits were presented in 2007 and 2012, inconsistent with the DAMA signal reports for masses above 20 GeV. Using 24,324.3 kg•days exposure, low-mass WIMP signals below 20 GeV were disfavored in 2014.

COSINE

The KIMS and DM-Ice groups have joined forces to make a new detector consisting of an array of NaI(Tl) scintillating crystals to confirm or refute the DAMA/LIBRA results. , the 100 kg COSINE-100 experiment had been installed at Y2L. In September 2016, physics data started to be collected. The next version of the COSINE detector, COSINE-200, will be constructed in Yemi Laboratory in Jeongseon County. The COSINE-100 published its first results on 5 December 2018 in ''

Nature Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans are ...

''; they concluded that their result "rules out WIMP–nucleon interactions as the cause of the annual modulation observed by the DAMA collaboration". This rejection applies only to WIMPs with one of the 18 tested masses, exhibiting spin-independent interactions with sodium or iodine nucleons, within the context of a standard dark matter halo model. In November 2021 new results from COSINE-100 experiment from 1.7 years of data collection have also failed to replicate the signal of DAMA. In August 2022 COSINE-100 applied an analysis method similar to one used by DAMA/LIBRA and found a similar annual modulation suggesting the signal could be just an statistical artifact supporting an hypothesis first put forward on 2020.

References

External links

Official page (English)
{{Underground laboratories Experiments for dark matter search Science and technology in South Korea