Hundreds of scientists and members of the general public were up at 2 a.m. Wednesday morning, crowded into an auditorium at Fermilab in west suburban Batavia. They were there to hear a groundbreaking announcement, coming to them via a live video stream from the CERN laboratory near Geneva.

“When the end of the second talk came, there was a standing ovation that lasted 3, 4, maybe even 5 minutes from the people in attendance,” said Rob Roser, a Fermilab scientist.

Roser and the rest of the crowd were applauding news that they had looked forward to hearing for decades: Scientists had finally observed the elusive Higgs boson particle. Dozens of Fermilab scientists worked with the team that produced the results that were announced in Switzerland.

“It’s certainly the biggest discovery in the last 40-50 years in particle physics,” said Roser. “And so it does change the way theorists think about how they describe the universe.”

The existence of the Higgs boson was first proposed in 1964 to explain how other particles have mass. Fermilab had sought the Higgs boson for a decade with its own particle accelerator and released its own findings earlier this week that suggested the presence of the particle. But Roser says the European accelerator, which is capable of producing far more data, yielded more conclusive evidence.

“There were times when I myself didn’t know whether we would ever get to see this day – not because we couldn’t do it, but whether it was real or not,” said Roser. “It’s been such a hard slog that I wasn’t sure.”

Roser said the next several years in particle physics will likely focus on investigating the behavior of the Higgs boson.