Kate Becker The Visible Universe
Kate Becker The Visible Universe

Watching the news while I got ready this morning, I heard a feel-good report about a family that had just welcomed their first baby girl in four generations. Over the course of 101 years, they got one baby boy after another, after another, after another — seven total — until finally, this month, a little girl was born. "What are the chances?" the excited host gushed.

Well, what are the chances?

Assuming that each baby has 50/50 odds of being a boy or a girl, there is a one in 128 chance of getting seven boys in a row. Slim odds for my family or yours, maybe, but given the number of families in the United States, not so very unusual after all. In fact, there must be loads of families with seven consecutive boys (or girls) who never make it onto the morning news.

Yet, being human, we look for meaning in the randomness. We find patterns where they don't exist. Coincidences calcify into superstition, and before you know it you're digging in the hamper trying to find your lucky underwear because today's the day of your big presentation at work. But how can we tell the difference between real connections and random chance? That's where statistical significance comes in.

Scientists usually consider a result "real" when the odds of a fluke sink to one in 3.5 million. ("Five-sigma" in stat-speak.) That's the threshold that data from the Large Hadron Collider had to meet before physicists could confidently declare that they'd "discovered" the Higgs boson.


Late last year, physicists announced that they'd found surprising "bumps" in data from two LHC experiments, ATLAS and CMS, representing extra pairs of photons coming out of the LHC's collision cascade — bumps that couldn't be explained by any particle known to physics. While the odds of each experiment picking up the extra photon pairs individually work out to about one in 10 or 20, physicists were intrigued to find that both experiments spotted the excess at about the same mass. Far short of the five-sigma limit, but still worthy of thought and attention.

If the bumps are real, what are they? Physicists have proposed hundreds of ideas; according to one count, there are more than 250 articles on the subject on arXiv, a website where physicists share papers that haven't yet been peer reviewed. The journal Physical Review Letters winnowed that pack down to four, which it published earlier this month. Three of the four papers propose that the extra photons are due to some new boson about six times as massive as the Higgs. (In addition to the Higgs, the boson family includes the particles that carry the fundamental physical forces; they follow strange rules that allow many to occupy the same quantum state at once.) The fourth paper argues that the experiments might be seeing traces of an even heavier particle.

So how do we know if this bump is real or just a fluke?

As usual, physicists need more data, and they are already busy collecting it. They hope to know more by this summer or fall. If the bump is real, it could be our first taste of physics beyond the Standard Model that physicists have spent decades assembling. For that reason, many will be rooting for it to be more than a fluke. So stay tuned — and don't forget your lucky underwear.
