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To solve their mysteries, the LHC's scientific sleuths will use the latest and greatest tools of the trade, built at a cost of billions of dollars. The two main detectors — ATLAS (A Toroidal LHC ApparatuS) and CMS (Compact Muon Solenoid) — are structured like the layers of an onion to spot different kinds of particles:
# Trackers: Both detectors have tracking devices at the center to follow the paths of short-lived particles.
# Calorimeters: The next layers are two different types of calorimeters that measure the energies of the particles given off. One captures electromagnetic energy, while the other captures the energy from particles such as protons, neutrons and pions.
# Magnets: Huge magnets are built into each detector to bend the paths of the particles so they can be identified by their charge.
# Muon detectors: The outer layers of the detector track the paths of muons, particles that can't be stopped by any of the inner layers.

Probing the smallest scales of matter requires some of the biggest machines ever devised. ATLAS is the largest of all detectors, measuring 151 feet long and 82 feet high — bigger than your typical apartment building.

"It has an awful lot of free space inside," CERN theoretical physicist John Ellis explained. "The reason for that is, they want to be able to measure particles which come out of the collision ... even if the interior of the detector is so clogged with collision products they can't measure them properly there."

Over on the other side of the LHC's ring, CMS takes up less than half as much space as ATLAS but weighs almost twice as much. It contains more iron than the Eiffel Tower, built into alternating magnetized layers with particle detectors like a metallic jelly roll. CMS' built-in magnets and its expensive fine-resolution silicon tracker are part of a different strategy to do the same things that ATLAS does.

"You get big arguments between the ATLAS guys and the CMS guys as to which is the best way to measure these particles," Ellis said. "ATLAS is going to bend them that way, CMS is going to bend them this way, and we'll see in a few years' time which is the better idea."

ALICE: The big bang in the machine
ATLAS and CMS get most of the attention, but the contraption that best merits the title of "Big Bang Machine" is about a mile (1.5 kilometers) down the road from ATLAS. The ALICE detector (A Large Ion Collider Experiment) is designed exclusively to study the stuff that the universe was made of less than a millionth of a second after the big bang.

ALICE will run for only about a month out of every year, conducting experiments that will require the collider to switch over from smashing protons to smashing lead ions, which are 100 times heavier than protons. The high-energy collisions should blast those ions so thoroughly that, for just an instant, they turn into a plasma of free-flying quarks plus gluons, the particles that usually bind quarks together.

Past experiments indicated that the quark-gluon plasma behaved like a liquid. When ALICE gets up and running, "then maybe we reach the gas phase," said Jurgen Schukraft, CERN's spokesperson for the ALICE experiment. That would be something never before seen in the cosmic scheme of things.

LHCb: The mystery of antimatter
The fourth detector is also designed to answer a specific cosmic question. LHCb will study particles containing particular "flavors" of quarks and antiquarks, known as B mesons and anti-B mesons, with the aim of figuring out why matter has a huge edge over antimatter in our universe.

Earlier studies revealed that the particles and antiparticles decayed differently, which runs counter to the idea that matter and antimatter should be in symmetry. LHCb will follow up on those studies, using a battery of high-tech detectors that are lined up on one side of the collision point. Among those instruments are a tracker that can locate particles with a precision of 10 microns, or a tenth the width of a human hair.

Two smaller experiments round out the ring: LHCf, which studies cosmic-ray-like events near ATLAS; and TOTEM, which measures the effective size of protons using a detector near CMS.

The Grid: Getting out the data
The LHC is designed to produce as many as 600 proton collisions per second, and that creates a flood of digital data that gushes out from the detectors' wiring. If you were to put all the data from one of the main detectors onto CDs, the stack of disks would pile up to the orbit of the moon in six months. The challenge is to pick out only the most promising readings.

Each of the detectors uses "triggers" to pick out the good stuff. Only about 100 events per second are sent to thousands of computers and tape drives at CERN for storage. It's like narrowing down that moon-high stack of CDs to a stack that's only 6 miles high — which is still high enough for a transcontinental jet to run into.

To get the data out to researchers around the world, CERN has set up a multi-tier computer network called the Grid. Digital information goes out to the "Tier 1" data centers on a fiber-optic network at a rate of up to 10 gigabits per second — or roughly 1,000 times the speed of a typical cable Internet connection.

If the system works, it could set the model for future computing — not only for physics but also for other high-end applications such as climate simulation, genetic analysis and petroleum prospecting. Just as the World Wide Web was the best-known spin-off from CERN's LEP experiment back in the 1990s, the Grid could well become the LHC's most visible legacy.

Magnet for innovation
Who will benefit the most from that legacy? The Grid may distribute the data across the world — but it's hard to argue with the idea that Europe's 21st-century wonder of the world will serve as a magnet for innovation over the next decade.

That has sparked more than a few cases of "collider envy" among American researchers, and some worry about the prospects of a reverse brain drain. Michio Kaku, a theoretical physicist at the City College of New York, is already noticing a trend in his colleagues' travel plans.

"They're going where the action is, and that is Europe," Kaku said.

Chapter 4: Europe pulls ahead in scientific race
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