Most of the matter in the Universe is made not of stuff we understand, but of invisible “dark matter” particles. We have yet to observe these mysterious particles on Earth, presumably because they interact so weakly with normal matter. The high energy collisions in the Large Hadron Collider provide our best current hope of making dark matter particles, and thus giving us a better understanding what most of the Universe is made of.

ATLAS,physics briefing,updates
The figure shows the density of allowed supersymmetric models before and after the ATLAS Run-1 searches. The missing points have been ruled out by the LHC data. The x-axis shows the mass of the supersymmetric dark matter particle, while the y-axis shows the predicted density of those particles in the universe. (Image: CERN)

One of the most popular theories to explain dark matter – at the level of individual particles – is known as supersymmetry. As yet, none of the various exotic partner particles predicted by supersymmetry have been seen, but many physicists believe that dark matter could be among them. As supporters (and critics) of the various theories gather in California to discuss their latest findings, the ATLAS experiment has released the most comprehensive summary to date of the interpretations of their experimental results (see link below).


The high energy collisions in the Large Hadron Collider provide our best current hope of making dark matter particles, and thus giving us a better understanding what most of the Universe is made of.


The results (one example shown in the figure below) show how 22 different searches for supersymmetric particles have been eating away at the allowed masses of dark matter particles and their supersymmetric siblings. As well as direct searches, the paper also investigates the indirect effects that these new particles would have on behaviour of existing particles, including the recently-discovered Higgs boson. Of the combinations of masses that were examined in detail, about 40% of them were found to be ruled out by the current ATLAS searches. However, there remain plenty of other combinations (particularly those with heavier particles) which might offer a better theory of Nature. Many of these can be tested with the 13 TeV collisions already taking place at CERN, so there’s plenty of exciting work still ahead…

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