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The latest data from CERN hints at a whole new force of nature

When Cern’s gargantuan accelerator, the Large Hadron Collider (LHC), fired up ten years ago, hopes abounded that new particles would soon be discovered that could help us unravel physics’ deepest mysteries. Dark matter, microscopic black holes and hidden dimensions were just some of the possibilities. But aside from the spectacular discovery of the Higgs boson, the project has failed to yield any clues as to what might lie beyond the standard model of particle physics, our current best theory of the micro-cosmos.

So our new paper from LHCb, one of the four giant LHC experiments, is likely to set physicists’ hearts beating just a little faster. After analyzing trillions of collisions produced over the last decade, we may be seeing evidence of something altogether new – potentially the carrier of a brand new force of nature.

But the excitement is tempered by extreme caution. The standard model has withstood every experimental test thrown at it since it was assembled in the 1970s, so to claim that we’re finally seeing something it can’t explain requires extraordinary evidence.

Strange anomaly

The standard model describes nature on the smallest of scales, comprising fundamental particles known as leptons (such as electrons) and quarks (which can come together to form heavier particles such as protons and neutrons) and the forces they interact with.

There are many different kinds of quarks, some of which are unstable and can decay into other particles. The new result relates to an experimental anomaly that was first hinted at in 2014, when LHCb physicists spotted “beauty” quarks decaying in unexpected ways.

Specifically, beauty quarks appeared to be decaying into leptons called “muons” less often than they decayed into electrons. This is strange because the muon is in essence a carbon-copy of the electron, identical in every way except that it’s around 200 times heavier.

You would expect beauty quarks to decay into muons just as often as they do to electrons. The only way these decays could happen at different rates is if some never-before-seen particles were getting involved in the decay and tipping the scales against muons.

While the 2014 result was intriguing, it wasn’t precise enough to draw a firm conclusion. Since then, a number of other anomalies have appeared in related processes. They have all individually been too subtle for researchers to be confident that they were genuine signs of new physics, but tantalisingly, they all seemed to be pointing in a similar direction.

Image of the LHCb experiment.