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What Mystery Lurks in Data from LHC’s More Powerful Second Run?

ByTim De ChantNOVA NextNOVA Next

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Today, physicists announced the first results from the second, more powerful run of the Large Hadron Collider. While they found nothing definitive, they aren’t ruling out a new discovery just yet.

Even before the seminar started, news had leaked out that there was a curious result representing two photons around 750 GeV. When the data was presented, the significance of the finding wasn’t quite high enough for the result to officially rate as “interesting” by physicists’ high standards, but it was enough to pique their curiosity.

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The ATLAS detector witnesses a collision on September 29, 2015.

“This is also how we found the Higgs,” said Greg Kestin, a particle physicist at Harvard University and a digital associate producer at NOVA. But, he cautioned, the diphoton peak may also be nothing. “We’ve seen signals this significant in LHC data go away.”

The significance levels are come close to 3 sigma in cases, but drop well below after correcting for the “look-elsewhere effect,” or the fact that large data sets can potentially produce apparently significant results that don’t have any real meaning. Here’s theoretical physicist Matt Strassler, writing at Of Particular Significance:

The diphoton bump seen, with moderate significance in ATLAS and low significance at CMS, is very interesting, but without more information and more thought and discussion, it’s premature to say anything definitive.

While it is a bit too early to say anything definitive, there is some speculation as to what the diphoton signals—if significant—could represent. One is that we’re seeing the decay of a Higgs boson into quarks, a predicted result of the Composite Higgs Model. Another is that physicists have found a second Higgs, a “twin” as predicted by other models.

What we do know is that they probably haven’t found evidence of supersymmetry yet, Kestin said.

Image credit: CERN