Almost everything is missing. And a team of physicists is trying to find all of it.
The universe as we know it includes about a tenth of the total stuff that’s out there. The rest? Missing. Invisible. Undetectable, except through the effects of its gravity on the fraction of stuff that we can see. Researchers call that missing stuff the dark sector — the class of energetic and massive particles that seemingly must exist out there somewhere but that don’t interact with luminous matter (the stuff we’re made of, along with everything we can see) in any way we can detect.
There’s a new project at the National Institute for Nuclear Physics in Italy that’s going to try to unlock all that dark stuff using the theoretical dark photon (the dark-sector version of regular light-carrying photons) as the key. And if they actually find the dark photon, it will provide evidence for the universe’s fifth force — which would be huge news in physics.
According to a report in The Guardian, Italian researchers plan to bombard a diamond wafer with a beam of antimatter particles called positrons, which are the antimatter versions of electrons. Under normal circumstances, positrons and electrons that smash into each other annihilate each other, producing a pair of regular photons.
But if dark photons really exist, then every once in a while, a positron-electron annihilation should produce one. Instead of the interaction spitting out two regular photons, a dark photon and a regular photon would emerge side by side, The Guardian reported.