How physicists are probing the Higgs boson 10 years after its discovery

er Duarte kicked off his scientific career by witnessing the biggest particle physics event in decades. On July 4, 2012, scientists at the laboratory CERN near Geneva announced the discovery of the Higgs boson, the long-sought subatomic particle that reveals the origins of mass. Duarte was an eager graduate student who’d just arrived at CERN.

“I was physically there maybe a week before the announcement,” Duarte says. As buzzing throngs of physicists crowded together to watch the announcement at CERN, Duarte didn’t make it to the main auditorium. That space was for VIPs — and those determined enough to wait in line all night to snag a seat. Instead, he says, he found himself in the basement, in an overflow room of an overflow room.

But the enthusiasm was still palpable. “It was a very exciting time to be getting immersed into that world,” he says. Since then, he and thousands of other physicists from around the world working on CERN experiments have gone all out exploring the particle’s properties.

Scientists predicted the existence of the Higgs boson back in 1964, as a hallmark of the process that gives elementary particles mass. But finding the particle had to wait for CERN’s Large Hadron Collider, or LHC. In 2010, the LHC began smashing protons together at extremely high energies, while two large experiments, ATLAS and CMS, used massive detectors to look through the debris. The particle’s discovery filled in the missing keystone of the standard modelof particle physics. That theory explains the known elementary particles and their interactions. Those particles and interactions are behind just about everything we know. The particles serve as building blocks of atoms and transmit crucial forces of nature, such as electromagnetism. And the mass of those particles is key to their behavior. If electrons were massless, for example, atoms wouldn’t form. Without the Higgs boson, then, one of scientists’ most successful theories would collapse.

The Higgs boson discovery dominated headlines around the globe. About half a million people tuned in to watch the livestreamed announcement, and footage from the event appeared on more than 5,000 news programs. Even oddball minutiae made it into the press, with a few articles analyzing the physicists’ use of the often-scorned font Comic Sans in their presentation. Little more than a year later, the discovery garnered a Nobel Prize for two of the scientists who developed the theory behind the Higgs boson, François Englert and Peter Higgs — for whom the particle is named. Now, as the discovery turns 10 years old, that initial excitement persists for Duarte and many other particle physicists. As a professor at the University of California, San Diego and member of the CMS experiment, Duarte’s research still revolves around the all-important particle. Progress in understanding the Higgs has been “stunning,” he says. “We’ve come so much farther than we expected to.”

Physicists have been working through a checklist of things they want to know about the Higgs boson. They spent the last decade cataloging its properties, including how it interacts with several other particles. Though measurements have so far been in line with the predictions made by the standard model, if a discrepancy turns up in the future, it may mean there are unknown particles yet to be discovered.

And there’s still more on the agenda. An especially important item is the Higgs boson’s interaction with itself. To help pin down this and other Higgs properties, scientists are looking forward to collecting more data. Scientists turned on an upgraded LHC for a new round of work in April. At the time of the Higgs discovery, collisions at the LHC reached an energy of 8 trillion electron volts. Collisions are expected to roll in at a record 13.6 trillion electron volts starting July 5, and data-taking will continue until 2026. These higher energies offer opportunities to spot heavier particles. And the High-Luminosity LHC, a more powerful iteration of the LHC, is expected to start up in 2029.

“Finding a particle, it sounds like the end of something, but it’s really only the beginning,” says experimental particle physicist María Cepeda of CIEMAT in Madrid, a member of the CMS collaboration. 

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