Elementary particles

There’s invisible, undetectable stuff all around us, and we call it dark matter. There’s plenty of evidence that this stuff is very real, but what exactly is dark matter? How do we know it’s there? And how are scientists looking for it?

CERN’s Large Hadron Collider probes the fringes of known physics, and now the facility has found particles not behaving as predicted. While it’s early days, the discovery hints at the existence of new particles or forces beyond the Standard Model.

In January scientists reported the detection of very low-frequency gravitational waves. Now astrophysicists have investigated two possible sources – the universe cooling down after the Big Bang, and a field of particles that could be dark matter.

Dark matter should outnumber regular matter five to one, yet it remains frustratingly elusive. But there might be ways to spot it, and now astronomers have scanned neutron stars for telltale signals of a proposed dark matter particle called an axion.

An extensive search for a hypothetical particle has turned up empty. The sterile neutrino is a proposed subatomic particle that could even be a candidate for the mysterious dark matter, but two new experiments have all but ruled it out.

An experiment designed to hunt for ever elusive dark matter has returned some strange and exciting signals. Out of the three possible explanations, one is unwanted interference – while the other two would herald new physics.

There are billions of tiny particles called neutrinos streaming through your body right now. But where did they come from? Researchers have now traced back some ultra-high energy neutrinos to their points of origin – radio flares from raging quasars.

Dark matter is believed to outnumber regular matter by a ratio of five-to-one, but so far it’s never been directly detected. Now, nuclear physicists have proposed a new candidate particle that might make up the stuff – and we’ve already found it.

The detection of the Higgs boson at CERN in 2012 is one of the biggest scientific discoveries of the decade. Now the ATLAS and CMS Collaborations have made the most precise measurement of its mass to date.

Rather than trying to see dark matter, a new experimental design from Stockholm University listens for it instead, using an “axion radio.”

Although the many experiments searching for evidence of dark matter have yet to turn up any solid proof yet, they are making other amazing discoveries. The XENON1T experiment has now revealed the longest half-life ever seen in an element, which is far, far longer than the age of the universe.

If you throw a particle at a wall, there’s a chance that it will suddenly appear on the other side. This is thanks to a phenomenon known as quantum tunneling, and now a team of physicists has measured just how long that process takes.