A Day at the Atom Smasher

On a chilly November morning, Jeremy Love (GRS’10) is standing in front of a large, wooden globe of a building outside Geneva, Switzerland, on the Meyrin campus of CERN (Conseil Européen pour la Recherche Nucléaire), an international physics research center also known as the European Organization for Nuclear Research. Love’s a skinny guy with a dark scruff of beard. He’s wearing jeans, a sweatshirt, and an olive backpack, and looking pretty casual for somebody who aims to help solve the mysteries of the universe by creating millions of mini–big bangs.

All that science will take place about 100 meters below ground in the Large Hadron Collider (LHC), enclosed in a 27-kilometer concrete tunnel that actually crosses the border between Switzerland and France. The LHC is the world’s most powerful atom smasher, a machine that physicists have been anticipating for decades. It was finally turned on September 10 — and then it promptly broke down, launching a laborious eight- to ten-month repair process.

Love arrived at CERN last June, and he’ll be here until the summer of 2010, part of a team of Boston University physicists attached to one of the LHC’s main particle detectors, a five-story bundle of trackers, calorimeters, magnets, and other instrumentation known as ATLAS. Inside the detector, protons will collide at nearly the speed of light, and physicists such as Love will sort through the debris looking for new particles that might help explain how the universe evolved.

The collisions in the LHC will reach energy levels seven times more powerful than any previous experiment has achieved. “And the higher energy you reach, the earlier in the universe you’re looking, because fractions of a second after the big bang, the universe’s energy was much more concentrated,” Love says. Heading off to a wooden building that sits atop ATLAS, he opens the door to reveal a cavernous room, crisscrossed with orange, green, and yellow girders, ventilation pipes, and a shoulder-high steel fence that rings two massive holes on either end of the concrete floor.

“You technically need a hard hat to be in here, but I think we’ll be all right,” says Love, ducking under some yellow caution tape and walking around to a short catwalk above one of the pits. Looking down into the guts of ATLAS (right), the top of the “muon system” — part of which was built at BU under the leadership of Steve Ahlen, a College of Arts and Sciences professor of physics — is visible. After other parts of the detector have tracked and trapped most of the charged particles that spray from a proton collision, this outermost system will measure the trajectories and energy of muons (like electrons, but heavier). And it’s this muon data that Love will eventually comb through for evidence of particles never before observed.

A siren sounds, and a yellow light flashes on a crane hovering over the opposite pit. They’re moving a piece of the detector, Love explains, part of the laborious repair work under way ever since a faulty electrical connection led to a major leak of liquid helium (used to keep the LHC colder than space) and forced the shutdown of the proton beam in late September. The experiment won’t start up again for at least six months, says Love, because everything must be fixed within the relatively tight confines of the LHC tunnel.

“It’s like a ship in a bottle,” he says. “To get to interior pieces, they have to move the outside pieces. So there’s this sort of intricate dance of how things are uncovered and repaired.”

Because the beam is shut down, Love spends a lot of his time down in the ATLAS experimental cavern 100 meters below, performing routine maintenance on the muon system, harnessed for safety as he tinkers dozens of feet off the ground. When the beam eventually comes back online and the proton collisions begin at a rate of thousands every second, Love will start analyzing the data, using specially designed software to sift through the collisions looking for the telltale signals of new particles. The LHC will produce enough data every year to roughly double all the information currently on the Internet.

The hope for that information is to help scientists discover what’s beyond the Standard Model of particle physics, which describes the simplest known particles (such as electrons and quarks) and the forces that act on them (such as electromagnetism and the force responsible for nuclear decay). For decades, this model has left particle physicists “unsatisfied,” as Love puts it — the model neglects gravity and offers no explanation for the imbalance of matter and antimatter, or “dark matter,” a phenomenon indicating that most of the universe’s mass is invisible, because it doesn’t emit light. In addition, the model’s explanation of why some particles have mass and others, such as photons, don’t, predicts the existence of a particle (known as the Higgs, named after the theorist who proposed it) that has yet to be observed.

In the last few decades, several theories have been proposed to explain what the Standard Model doesn’t. Each of them predicts the existence of new particles that LHC scientists will be hunting for in the years ahead. First, however, they’ll need to spend a lot of time getting the proton beams to curve just right and calibrating every bit of the particle detectors.

“It’s difficult, when you’re working on an experiment this big, not to get lost in the details and forget that there is a big picture,” says Love, who first became interested in cosmic questions when he read theoretical physicist Stephen Hawking’s A Brief History of Time. But even with the beam temporarily shut down, he is thrilled about working at CERN.

“If you’re not motivated by understanding the universe, it’s probably not going to keep you interested,” he says. “What keeps everybody here motivated is the drive to understand what nobody else understands.”

Chris Berdik can be reached at cberdik@bu.edu.