The first direct investigation of inelastic amplified dark matter with a terrestrial detector

A team of researchers in the Republic of Korea, the United States, Brazil, Indonesia, and the United Kingdom recently conducted a direct search for Inelastic Boosted Dark Matter (IBDM) using a detector. earthly. Their study, published in Letters of physical examination (PRL), is the first to experiment with IBDM using a terrestrial detector.

Observations collected as part of earlier astrophysical studies suggest that the dominant matter component of the universe is not an ordinary matter, but a non-baryonic dark matter. Researchers have made enormous efforts to search for dark matter through direct detection, indirect detection and collider experimentation; however, their attempts have not been successful so far.

This lack of success has prompted them to look for other types of dark matter, such as light mass models or relatively relativistic dark matter, which would have significantly different signatures in the detectors. It is precisely because these new types of dark matter produce unconventional signatures that very few of them have been the subject of traditional dark matter experiments.

"Although scientists have consistently been researching WIMP (massive particles interacting weakly) dark matter in recent decades, no clear signal has yet been observed," said Hyun Su Lee, a researcher at the Institute. for Basic Science from Daejeon, Korea. performed the recent study, told Phys.org. "This has motivated researchers for other types of dark matter, which can give very different signals in the detector." One idea is to look for multicomponent dark matter, in which case each component of the dark matter is probably dark matter WIMP, but a different mass. "

A few years ago, researchers from the University of Maryland and MIT presented a new model describing a relativistic dark matter particle, enhanced by the annihilation of heavier dark matter particles at the center of the galaxy or sun. Depending on their model, this would require at least two species of dark matter particles, including a multicomponent dark matter.

Dark matter candidates with a heavier mass can decompose into a light dark matter. Since mass is equivalent to energy, in the case of multicomponent dark matter, the mass differences between the different components would lead to a high speed of light dark matter. The term "amplified dark matter" therefore essentially means that the incident dark matter has a relatively high speed.

"The expected signal of high-speed dark matter is an energy electron retreat, while the typical dark matter brings a low-energy nuclear recoil," Lee explained. "This theory has developed considerably in recent years, after which theorists began to think about inelastic scattering, because of the many components of dark matter."

In chemistry and physics, inelastic scattering is a fundamental process in which the kinetic energy of an incident particle is not conserved but is lost or increased. Researchers at CERN, as well as other institutions in Korea and the United States have theorized an inelastic interaction of boosted dark matter. According to their theories, relativistic dark matter interacts with the target material by inelastic electron scattering, creating a heavier state that will later produce standard model particles, such as electron-positron pairs.

"In inelastic scattering, the first energy electron is produced with an extra particle from the dark sector," Lee explained. "Such a dark sector particle is breaking down into a pair of electron-positrons with some displacement.No experiment having so far studied this type of signals closely, we have so thought that it could be a good alternative scenario to explain the problem of dark matter. "

In their study, Lee and his colleagues conducted the first direct search of IBDM with a terrestrial detector. They essentially immersed eight Nal (TI) crystals with a total mass of 106 kg in a 2,200 liter liquid scintillator surrounded by heavy shields to block the radioactive backgrounds.

"We used both NaI (Tl), 106 kg and LS, 2 tons, as the active detector to look for an electron energy pair + electron positron that deposited energies in two different detector components," Lee said. "Because of the large mass of the detector and its many components, it reaches a relatively good sensitivity for these types of signals."

Unfortunately, Lee and his colleagues were unable to detect IBDM signals in their data. Nevertheless, this is a pioneering study because no one has used detectors before to search for this particular type of dark matter.

Their work is part of a larger project, dubbed COSINE-100, which specifically aims to test the annual modulation of dark matter observed by the DAMA experiment. The researchers believe that subsequent searches for IBDM signals using the same detector or other dark matter detectors at the ton scale will be more successful.

"For optimized dark matter research, we will improve our analysis by using a dataset about 10 times larger than the one we already have on disk," Lee said. "We are also planning to search for elastic broadcast channels and we expect that an updated search will explore large spaces of parameters that have not yet been explored in any other experiment."

© 2019 Science X Network