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Current Affairs

Scientists hunt for dark matter signals

Date: 07 May 2020 Tags: Space

Issue

A new study suggests new paths for catching the signals of dark matter particles that have their energy absorbed by the nuclei.

 

Background

Though about 85 percent of the total mass of the universe is made of dark matter, it doesn't interact with photons of light, and also cannot be detected by observing electromagnetic radiation. This is so because dark matter is composed of particles that do not absorb, reflect, or emit light.

 

Details

  • The absorption process could give an affected atom a kick that causes it to eject a lighter, energized particle such as an electron, and it might produce other types of signals, too, depending on the nature of the dark matter particle.

  • The study focuses mostly on those cases where an electron or neutrino is ejected as the dark matter particle strikes an atom's nucleus.

  • The study proposes that some existing experiments, including ones that search for dark matter particles and processes related to neutrinos—ghostly, detectable particles that can pass through most matter and have the ability to change into different forms—can easily be broadened to also look for these absorption-related types of telltale dark matter signals.

  • Physicists are now considering other places that dark matter particles may be hiding, and other particle possibilities such as theorized "sterile neutrinos" that could also be brought into the family of particles known as fermions—which includes electrons, protons, and neutrinos.

  • The researchers note that the range of new signals they are focusing on opens up an ocean of dark matter particle possibilities: namely as-yet-undiscovered fermions with masses lighter than the typical range considered for WIMPs.

  • The study team considered absorption processes known as "neutral current," in which nuclei in the detector material recoil, or get jolted by their collision with dark matter particles, producing distinct energy signatures that can be picked up by the detector.

  • The charge current process can also involve nuclear decay, in which other particles are ejected from a nucleus as a sort of domino effect triggered by the dark matter absorption.

  • Experiments that have large volumes of detector material, with high sensitivity and very low background "noise," or unwanted interference from other types of particle signals, are particularly suited for this expanded search for different types of dark matter signals.

 

Dark matter

  • Roughly 80% of the mass of the universe is made up of material that scientists cannot directly observe. Known as dark matter, this bizarre ingredient does not emit light or energy.

  • Unlike normal matter, dark matter does not interact with the electromagnetic force. This means it does not absorb, reflect or emit light, making it extremely hard to spot.

  • In fact, researchers have been able to infer the existence of dark matter only from the gravitational effect it seems to have on visible matter.

  • Dark matter seems to outweigh visible matter roughly six to one, making up about 27% of the universe.