To manage this onslaught the teams’ computers have to perform triage, and winnow those events to a couple hundred per second. That is dangerous, Dr. Gianotti said, “because we are looking for something rare.” The Higgs occurs once in every trillion events, she said.

Contending Armies

The competition between Atlas and the C.M.S. is in keeping with a long tradition of having rival teams and rival detectors at big experiments to keep each other honest and to cover all the bets. As Dr. Mangano put it, “If you screw it up, others are here to crucify you.”

At the Fermilab Tevatron, the teams, several hundred strong, are called CDF and D0. In the glory years 20 years ago at Cern, they were called UA1 and UA2. Over the years, as the machines have grown, so have the groups that built them, from teams to armies, 1,800 people from 34 countries for Atlas and 2,520 from 37 countries for the C.M.S. The other two experiments — Alice with 1000 scientists, and LHCb with 663 — are only slightly smaller.

Robert Cousins of U.C.L.A. and C.M.S. joked that he was old enough so that after 25 years in the business “half my friends are on Atlas, the others on C.M.S.” Dr. Jenni said all 1,800 Atlas scientists would have their names on the first papers out of the collider, adding: “The people who work in the pit make as important a physics contribution as those who end up in front of the computers. This is a big step in energy. It’s new territory, and that’s in the end why everyone is excited.”

At the end of the day, Dr. Mangano said, unless there is a major problem both machines will perform. “It will come down to sociology,” he said. “How quickly can they analyze the data? How do you manipulate and analyze the data? The process of understanding is long.”

There could be new phenomena, he added, new particles that theorists have not thought of.

Dr. Mangano pointed out that it had been a long time since high-energy physicists had made a fundamental discovery. And back then, when Dr. Rubbia was doing his Nobel work, there were well-defined theories of what would be found. Now, everything will be new.

“There are many students who have never seen data,” Dr. Mangano said. “I don’t know how much longer we can keep going like that.”