Particle Hunters Can Spend a Lifetime Searching for Answers

Particle Hunters Can Spend a Lifetime Searching for Answers

June 16, 2022 0 By bimola

IceCube is an example of how big science, and particularly particle physics, now often works on generational time scales. Getting from the idea of IceCube to actually drilling its neutrino sensors into a cubic kilometer of Antarctic ice to pinpointing a high-energy neutrino source took 30 years. In that time, key personnel retired, passed away, or moved on to projects offering more instant gratification. Whitehorn’s experience is the exception, not the rule—many scientists have devoted years, decades, or even entire careers to seeking results that never came.

The discovery of the Higgs boson took even longer than extragalactic neutrinos: 36 years from initial discussions about building the world’s biggest and highest-energy particle collider—the Large Hadron Collider (LHC)—to the now famous announcement of the particle’s discovery in 2012.

For Peter Higgs, then aged 83, the detection of his eponymous particle was a satisfying epilogue to his career. He shed a tear in the auditorium during the announcement—a full 48 years after he and others first proposed the Higgs field and its associated elementary particle back in 1964. For Clara Nellist, who was a PhD student working on the LHC’s ATLAS experiment in 2012, it marked a thrilling beginning to her life as a physicist.

Nellist and a friend turned up at midnight before the announcement with pillows, blankets, and popcorn and camped outside the auditorium hoping to get a seat. “I did that for festivals,” she says. “So why wouldn’t I do it for possibly the biggest physics announcement of my career?” Her determination paid off. “To hear the words ‘I think we have it!’ and the cheer in the room was just such an amazing experience.”

The Higgs particle was the last piece of the puzzle that is our best description of what makes up the universe at the smallest scales: the Standard Model of particle physics. But this description can’t be the final word. It doesn’t explain why neutrinos have mass or why there’s more matter than antimatter in the universe. It doesn’t include gravity. And there’s the small matter of it having nothing to say about 95 percent of the universe: dark matter and dark energy.

“We’re at a really interesting time because when we started, we knew the LHC would either discover the Higgs or rule it out completely,” says Nellist. “Now we have many unanswered questions, and yet we don’t have a direct road map saying that if we just follow these steps, we’ll find something.”

Ten years on from the Higgs discovery, how does she cope with the possibility that the LHC might not answer any more of these fundamental questions? “I’m very pragmatic,” she says. “It’s a bit frustrating, but as an experimental physicist I believe the data, and so if we do an analysis and get a null result, then we move on and look in a different place—we’re just measuring what nature provides.”

The LHC isn’t the only big science facility hunting for answers to these existential questions. ADMX might be the garage band to LHC’s stadium rockers in terms of size, funding, and personnel, but it happens to also be one of the world’s best shots at uncovering the hypothetical axion particle—a leading candidate for dark matter. And unlike at the LHC, ADMX researchers have set out a clear path to finding what they seek.