Was it a blip, or a breakthrough?

Scientists around the globe are revved up with excitement as the world's biggest atom smasher—best known for revealing the Higgs boson four years ago—starts whirring again to churn out data that may confirm cautious hints of an entirely new particle.

Such a discovery would all but upend the most basic understanding of physics, experts say.

The European Center for Nuclear Research, or CERN by its French-language acronym, has in recent months given more oomph to the machinery in a 27-kilometer (17-mile) underground circuit along the French-Swiss border known as the Large Hadron Collider.

In a surprise development in December, two separate LHC detectors each turned up faint signs that could indicate a new particle, and since then theorizing has been rife.

"It's a hint at a possible discovery," said theoretical physicist Csaba Csaki, who isn't involved in the experiments. "If this is really true, then it would possibly be the most exciting thing that I have seen in in my career—more exciting than the discovery of the Higgs itself."

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