Low-mass particle could lead to dark matter detection

Chuck Bednar for redOrbit.com – Your Universe Online

Even though dark matter is believed to make up 85 percent of the universe’s mass, no one has managed to detect the elusive material, but a new fundamental particle proposed by scientists at the University of Southampton could finally change that.

Dark matter is believed to exist because of the gravitation effect it has on stars and galaxies, the gravitational lensing (or bending of light rays) that occurs around these objects, and its imprint on the afterglow of the Big Bang (also known as the Cosmic Microwave Background).

Despite what the researchers call “compelling” indirect evidence to support its existence, and an immense amount of effort from astronomers, no one has been able to directly detect dark matter yet. Clues as to what it could be can be found through particle physics, however.

The standard view, the study authors explain, is that dark matter particles have a very large mass for fundamental particles, similar to those of heavy atoms. Lighter dark matter is unlikely due to several astrophysical regions, though some exceptions have been identified, they added.

The new study published earlier this week in the journal Scientific Reports presents the possibility low-mass dark matter particles exist and could be directly detected. These lighter particles would have been missed by all experiments conducted to date, the researchers claim, and neither constraints from particle physics nor cosmological observations can rule out their existence.

“Our candidate particle sounds crazy, but currently there seem to be no experiments or observations which could rule it out,” he added. “Dark Matter is one of the most important unsolved problems in modern physics, and we hope that our suggestion will inspire others to develop detailed particle theory and even experimental tests.”

The proposed lighter dark matter particle has a mass of just 100eV/c^2, or approximately 0.02 percent that of an electron, according to their research. Unlike heavier forms of dark matter, it would not interact with light, though it would surprisingly interact with normal matter.

Also, unlike other candidates, this low-mass dark matter may not even be able to penetrate the Earth’s atmosphere, rending detection from the ground unlikely. As a result, Dr. Bateman and his colleagues plan to incorporate the search for these particles into a space experiment planned by the Macroscopic quantum resonators (MAQRO) consortium.

By suspending a nanoparticle in space and exposing it directly to the flow of dark matter, the study authors believe that they may be able to observe it being pushed downstream. Monitoring the nanoparticle’s position could then shed new light on the existence of low-mass dark matter.

“At the moment, experiments on Dark Matter do not point into a clear direction and, given that also the Large Hadron Collider at CERN has not found any signs of new physics yet, it may be time that we shift our paradigm towards alternative candidates for Dark Matter,” said co-author Dr. Alexander Merle from the Max Planck Institute in Munich, Germany.

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