- Several researches are going on to find evidences of a hypothetical particle called dark photon.
- So far, physicists have come up with no proof.
- However, upcoming experiments will be more precise and sensitive to dark photon decay.
You might be aware of dark matter. It doesn’t emit any light or interact with observable electromagnetic radiation, and is thus invisible to the whole electromagnetic spectrum. Dark matter might not be the only hypothetical particle that exists alone in our galaxy. It might represent a fraction of unknown forces.
This possibility has led to the search of another hypothetical particle called dark photons. They’re quite similar to the typical photons but they’re exchanged between dark matter particles. Some model even suggests that they have mass.
Of course, any evidence of dark photons would be a major milestone; it could uncover some valuable facts about dark matter, which is much more complicated than presumed by most of the theories.
However, the latest findings at the Large Hadron Collider (LHC), the world largest particle collider, has revealed nothing. Although it came up with empty results, the range of possible values for strength of interaction between electromagnetic fields and dark photons has been narrowed.
Artwork by Sandbox Studio, Chicago with Ana Kova
The concept of Dark photons was proposed in 2008 as the force carrier of a new wide-range dark electromagnetism and gauge field acting on dark matter. We could theoretically detect it by mixing it with typical photons and their resulting impact of interactions of known particles.
Some scientists believe dark photons cause g-2 anomaly. However, they were later ruled out as a cause of anomaly by different studies and experiments at the Relativistic Heavy Ion Collider. Fermilab is now working on a new Muon g-2 experiment that is supposed to generate 4 times more accurate results than previous studies.
As we have mentioned, proton collision is one of the possible ways of producing dark photons that further decay into muons and antimuons. A research team operating Large Hadron Collider beauty detector with proton-proton collision data (obtained in 2016), found no clue of excess muons and antimuons.
However, they narrowed the electromagnetic coupling constraints for data photons decay. The long-lived photon decay ranges between 214 and 250 MeV/c2, whereas promptly decaying dark photons ranges from 10.6 to 70 MeV/c2.
Reference: Physics Review Letters | doi:10.1103/PhysRevLett.120.061801
The outcomes bode well for the experiments carried out in 2017, which were focused on uncovering dark photons’ decay products in the lower mass range. The researchers predict that the upcoming studies and experiments will be more precise and sensitive to decay of dark photons. By 2021, experiments could be at least several hundred times more accurate than what we have today.
DarkLight Experiment By MIT
DarkLight | Credit: Bateslab MIT
Researchers at Massachusetts Institute of Technology are also hunting for dark photons with an energy range of about 10 to 500 MeV/c2. The experiment, dubbed DarkLight, also focuses on finding dark gauge field by analyzing processes of a windowless hydrogen gas target.
So far, they have found nothing. But if the particle is discovered, it would become the 5th fundamental force of nature, joining the particles associated with electromagnetism, gravity, weak and strong nuclear forces.