In particle physics, failure isn’t necessarily a bad thing. In fact, it can generate as much excitement and curiosity as success.
As if to prove this point, two teams of particle hunters, one from the Large Hadron Collider in Geneva and the other from the IceCube neutrino detector in Antarctica, recently reported they had not found signs of new particles, as they had hoped.
“To be honest, I’m really excited about this IceCube result, because it was not actually what we expected,” says Janet Conrad, a professor of physics at MIT. “I see this as a real opportunity to go on another expedition. So I am really happy about it. I realize it’s hard to explain that to the world.”
IceCube was on the lookout for a theoretical particle called the sterile neutrino. After collecting five years of data, scientists now say with 99 percent confidence that the particle does not exist.
“The sterile neutrino would have been a profound discovery,” says physicist Ben Jones of the University of Texas, Arlington, who worked on the IceCube analysis. “It would really have been the first particle discovered beyond the Standard Model of particle physics.”
The Standard Model of particle physics “explains how the basic building blocks of matter interact, governed by four fundamental forces,” says the CERN website, the laboratory that is the one of world’s major hubs of particle physics and home to the Large Hadron Collider. The Standard Model has been the beating heart of particle physics since the 1970s, but still can’t explain some of the most profound mysteries of the universe, like the nature of dark matter and dark energy.
Scientists at CERN were responsible for the 2012 discovery of the Higgs boson, the fundamental particle described as the last piece of the puzzle in the Standard Model. They confirmed their discovery a second time, which was fantastic news in the physics world. But, like IceCube, they recently announced that another exciting discovery had, in fact, been an anomaly.
“We were over the moon when we discovered the Higgs boson,” says James Beacham, a post-doctoral researcher at Ohio State University who is also part of the ATLAS team at CERN. “Anything we find beyond that is going to be completely revolutionary, because it will be the first evidence we've seen of a fundamental particle outside of the wildly successful Standard Model. So, it's a really good example that both of these experiments happened, because we've both published ‘no results,’ in a sense, at around the same time. The message from the [CERN team] last week was not so much that this diphoton bumplet faded away — it was more that we have just recorded our initial findings at this kind of thing.”
The “bumplet" Beacham refers to was detected in 2015 in a number of experimental locations around the world and greeted with enormous excitement. It opened the possibility of a whole new kind of physics.
“The suggestive thing about it was that both us and the ATLAS experiment and the CMS experiment saw the same little bumplet at around the same place,” Beacham explains. “The theory community sort of ran with that and then the news media got in on it, so it became the topic of a lot of attention. Then we took about five times more data this year and it turned out that this little, not-so-suggestive bumplet turned into a nice smooth one. So, no new physics there.”
But the search goes on. Beacham likens it to exploring an alien planet.
“[W]e don't know what we're going to find,” he says. “We have probably two decades worth of research to do on this data, and we just got here. So it's our job to report back to home base, in a sense. If we go to an alien planet, we instantly look around to see if there are any big, fuzzy, easy-to-spot monsters. We don't see those, but we don’t just stop. We spend the next decade or two decades combing through the sand trying to find the hidden stuff that could be there.”