The 7,000-ton ATLAS detector was one of the two key instruments the Large Hadron Collider that found the Higgs.
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That happened in late spring. Gianotti's team and another led by Joe Incandela worked separately, and both turned their findings over exclusively to CERN research director Rolf Heuer. Thus, while the two team leaders knew that their own work was yielding positive results, only Heuer knew that they had both shot bull's-eyes.
"When I saw the first plot from Joe and the first plot from Fabiola, I thought, O.K., we have it," says Heuer. "When we all sat down together, I had to spell it out to them. They were reluctant to use the word discovery, but I persuaded them that yes, we can use it."
The announcement of that discovery was made on July 4 to an exuberant crowd of physicists at the International Conference on High Energy Physics in Melbourne. A somewhat dazzled-looking Peter Higgs, now 83, was in attendance and received a long and warm ovation. "It's an incredible thing," he said, "that it happened in my lifetime."
Through the Looking Glass
To fully fathom the implications of the find could take well beyond not only Higgs' lifetime but also those of many other, much younger physicists. Particles produced in colliders last only a few trillionths of a second before decaying into smaller, more fundamental ones. If the Higgs just discovered is merely part of an extended Higgs family--a real possibility--each of those members will have its own particular decay channel and could lead down different research paths.
Take dark matter. Galaxies are large enough and spin fast enough that by rights they ought to fly apart. The fact that they don't means the gravity from some unseen form of matter is holding them together. And in order to exert so much pull, it would have to be an awful lot of that matter--fully 80% of the universe. Most physicists believe that the invisible stuff is made of a particle of some kind. If that particle has mass, it's interacting with the Higgs. Find the Higgs responsible and you may pull back the curtain on what the dark particles are.
Dark energy is a different matter--a force that pulls the universe apart rather than holds it together, contributing to the steady expansion that has gone on since the Big Bang. Part of the chatter after the Higgs was found was that it could help explain that too. No one remotely knows how--dark energy is a much newer concept than dark matter--but there will likely be a stampede to publish all the same. "Oh my dear," says LHC and Caltech physicist Maria Spiropulu, "there will be approximately 2,000 papers next week connecting the Higgs to dark energy. Theorists are beasts like that."
Gravity itself, the universe's fourth great force and the one that is not addressed at all in the standard model, could also come in for some new understanding. One possibility is that gravitational attraction is also carried by a particle: a graviton. If so, one of the mysterious decay channels the Higgs travels may lead to its door too. All that, however, is for the years and the generations to come. And with the LHC still in its go-slow power-up mode and not even set to hit full throttle till the end of 2013, the hardware to do that work will only get better.