LHC Experiment Hints at Possibility of New Particle

The biggest particle accelerator in the world might have found a hint of an entirely new fundamental particle — or it might be seeing ghosts.

But even if it turns out to be nothing, particle physicists have written a spate of studies to coincide with the new experimental results, proposing different ideas about what might have been found. Theories in the new research papers range from positing new flavors of the Higgs boson (the particle thought to explain how other particles get their mass) to proposing candidates for dark matter.

If a new particle or particles turn out to be real, or if dark matter is confirmed, it would mean the reigning model of particle physics, the Standard Model, needs to be extended and possibly replaced.

The scientists working on the Large Hadron Collider, operated by CERN, outlined new data this week covering a year of observations from two different detectors inside the atom smasher — ATLAS and CMS.

The LHC data shows something tantalizing — a "bump" on the curve of particle events, centered at an energy level of 750 GeV. The bump showed up on both detectors, so at first blush it's less likely to be a fluke.

World's Most Complex Machine Smashes Atoms Once Again 2:23

The problem is that confidence in the data isn't as high as the scientists would like. To clinch a discovery of a new particle, physicists like to have what they call "5-sigma" certainty. Sigma is a measure of how likely it is that what you're seeing is by chance.

In this case, the result is 3.9 sigma at best, which is good enough to be intriguing, but not enough to say that anyone has seen a genuinely new particle. That said, many physicists seem confident that future data will show that there is something there.

"The event is very exciting," said Yasunori Nomura at the University of California, Berkeley, "even though it is not yet at the level we can call a discovery."

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