Super-smasher targets massive mystery
Chapter 1: Particle collider comes close to the big bang on a small scale
By Alan Boyle
updated 2:12 p.m. ET Sept. 8, 2008
MEYRIN, Switzerland - In the beginning was the big bang.
God may have been around before then — but as far as scientists are concerned, the big bang is as far back as they can go. And to get back there, they're getting ready to blast subatomic particles so energetically that the extreme conditions of the freshly born universe will be re-created on Earth.
Will those "little big bangs" crack age-old scientific mysteries? Or, despite repeated assurances from the world's top experts, will they create black holes that could gobble up the planet? After decades of preparation, scientists are finally switching on a machine that will separate the facts from what is plainly science fiction.
The machine is the $10 billion Large Hadron Collider, or LHC — the most powerful, most expensive particle-blaster ever invented. On Wednesday, Europe's CERN particle-physics lab is due to start shooting beams of protons through the LHC's 17-mile-round (27-kilometer-round) ring of tunnels beneath the French-Swiss border.
It will take months for the machine to reach full power. But eventually, those protons will be whipped up to 99.999999 percent of the speed of light, slamming together with the energy of two bullet trains colliding head-on. Underground detectors as big as cathedrals will track the subatomic wreckage on a time scale of billionths of a second. Billions of bits of data will be sent out every second for analysis.
As big as the numbers surrounding the LHC are, the mysteries it was built to address are bigger:
* What was the newborn universe made of?
* What causes things to have mass?
* Why is most of that mass hidden?
* Where did all the antimatter go?
* Is our entire universe a mere sliver of all that is?
"The LHC is the most powerful microscope that's ever been built," said John Ellis, a theoretical physicist here at CERN. "It will be able to explore the inner structure of matter on a scale that is 10 times smaller than anyone's been able to do before."
Ellis said the LHC also serves as "the most powerful telescope ever built," even though it looks inward rather than outward.
"We know that the way elementary particles interacted with each other controlled the very early universe," he explained. "So with the LHC we are able to, in some sense, re-create the conditions that existed in the universe when it was just a fraction of a second old — the sort of thing that the optical telescopes just can't see."
What's the point?
Past experiments in particle physics have yielded scores of practical spin-offs, ranging from new medical therapies to high-tech industrial materials — and even the World Wide Web, which you're using to read this report. But the potential for spin-offs isn't why more than 10,000 researchers around the world are looking forward so anxiously to the LHC.
"People ever since the ancient Greeks – and probably a long time before that – have wanted to understand how matter is made up, how it behaves, where the universe comes from,” said Ellis, surrounded in his office by stacks of research papers. “And so we are responding to that continuing human urge.”
The quest is not without controversy: Scientists say there's a chance that the LHC could create microscopic black holes, a phenomenon never before observed on Earth. They hasten to add that the tiny singularities will instantly pop out of existence, but that hasn't stopped critics from trying to block the collider's startup. Two of the critics have filed suit in federal court in Hawaii, seeking the suspension of LHC operations until more studies are done.
Responding to the critics, CERN has issued a series of reports explaining why the LHC will pose no threat. Ellis was one of the report's authors. "If the LHC were to make microscopic black holes, it would be tremendously exciting — and no danger," he said.
The 62-year-old London native has spent more than half his life at CERN, delving into topics ranging from dark matter to the theory of everything. Once the LHC is up and running, he expects to find out whether the theories he and other physicists have developed over all those years lead to solid evidence — or lead to a scientific dead end.
“Theoretically, that would be the most interesting possibility, because it would really mean that we had to tear up our notebooks of the last 45 years and start more or less from scratch,” Ellis said.
The God Particle
The theory described in all those notebooks is known as the Standard Model, which ranks among the scientific world's most successful theories. The Standard Model lays out a menagerie of subatomic particles and their interactions — and provides the basis for inventions ranging from television sets to microwave ovens to nuclear bombs.
Only one elementary particle predicted by the Standard Model has not yet been detected: the Higgs boson, which is thought to interact with other particles to give them mass. Without the Higgs, the big bang might have been an insubstantial flash in the pan — all energy, and no mass. Or so the theory goes.
The elusive Higgs boson looms so large as a gap in the Standard Model that Nobel-winning physicist Leon Lederman wrote a book about it called "The God Particle." (He joked that he wanted to call it the "Goddamn Particle," but his editor wouldn't let him.)
"This is in some sense the holy grail of particle physics, to find this missing link in the Standard Model," Ellis said. "So that's one thing that we're really looking forward to with the LHC. In fact, back when we persuaded the politicians to stump up the money to build the thing, that's probably what we told them."
Not even the LHC will be able to spot the Higgs boson directly. Instead, physicists will have to infer its existence through an analysis of the other particles that should be created when it decays. It's not an easy task, but Ellis believes the evidence should turn up within a year or two of the machine's startup.
Even that won't mark the end of the quest. Ellis compared the Higgs boson to a doorway that should lead beyond the Standard Model.
"I don't think that the Higgs door, if you like, is just closing off the room, and there is nothing beyond," he said. "I believe there's going to be a lot more physics beyond. What it's going to be, I don't know. Maybe it's supersymmetry. Maybe space has additional dimensions. Maybe it's something that we haven't thought of yet. I certainly hope it's something we haven't thought of yet. It would be great to come across a real surprise."
But Ellis and his colleagues at CERN have two nagging concerns in the back of their minds: What if somebody else finds the magic door first? Or what if they spent all these billions of dollars and there's no Higgs particle at all?
A competitive twist
Fifteen years ago, when Leon Lederman wrote "The God Particle," he thought the Higgs boson would be found in the Superconducting Super Collider, a project that was just getting started in Texas. That machine would have been four times as powerful as the LHC — but when the costs started running far beyond the initial estimates, Congress killed the program.
Over the decade that followed, U.S. scientists weren't just waiting for the LHC to be built: The focus shifted to the Tevatron collider at Fermilab in Illinois, which theorists figured might have just enough punch to pick up the Higgs' trail.
Last year, researchers at Fermilab passed the word that they had found some interesting data — readings that hinted at the presence of the Higgs but weren't yet solid enough to publish. That added a competitive twist to the grail quest.
"The longer we wait, the higher the probability that Fermilab discovers something that we wouldn't mind discovering ourselves here," Jos Engelen, CERN's chief scientific officer and deputy director general, said last year.
Beyond the God Particle
What if physicists don't find the God Particle they are expecting to see? Ellis acknowledged that was a possibility. "This might be a little bit difficult to explain to our politicians, that here they gave us 10 billion of whatever, your favorite currency unit, and we didn't find the Higgs boson," he said.
But Ellis has faith that even then, there'd be something to discover — maybe something even weirder and more wonderful than the Higgs boson.
"Probably the most likely option then might be extra dimensions," Ellis said. "And there are some ideas where if you have some additional dimensions of space, you could somehow do the job that the Higgs does in the Standard Model."
For years, string theorists have noted that their equations come out better if they assume that the universe has nine or 10 spatial dimensions instead of the three we can perceive. The LHC could provide the first evidence of those extra dimensions: Some theorists say the collisions could produce anomalously heavy particles, suggesting that part of their momentum was going into the extradimensional realm. Harvard physicist Lisa Randall estimates that the LHC could nail down the evidence for extra dimensions in five years.
Other theorists have focused on the idea that every subatomic particle should have an as-yet-undetected "supersymmetric" partner that mirrors many of the characteristics of the particles we know, but is dramatically different in other respects. The partners would have greater masses and a different spin, for example.
To date, no actual evidence of supersymmetry has been found. But if supersymmetric particles don't exist, then a lot of the theories that look beyond the Standard Model would have to be thrown out.
If supersymmetric particles do exist, they could account for a large part of the universe's dark matter. That's the 90 percent of all matter that scientists can detect only by its gravitational effect — a puzzle that has bedeviled astronomers for decades. "There are good reasons to think that these dark matter particles, if they exist, will be observable in the LHC," Ellis said.
Exploring the big-bang frontier
One of the LHC's detectors, known as ALICE, is devoted to studying the stuff that the universe was made of less than a billionth of a second after the big bang. Earlier experiments have hinted that the stuff was a super-hot liquid consisting of subatomic particles known as quarks and gluons.
For one month out of every year, the LHC will switch from smashing protons to smashing heavy lead ions, in an effort to re-create that quark-gluon soup and let ALICE analyze the recipe.
Yet another detector, LHCb, will study the tracks of particles containing specific types of quarks and antiquarks. The Standard Model predicts that equal amounts of matter and antimatter should have been produced in the big bang — but today, we see hardly any antimatter in nature. That's a good thing, because matter and antimatter annihilate each other when they come in contact, leaving pure energy behind.
LHCb will follow up on earlier experiments that suggest matter won out over antimatter because they somehow decay in different ways.
And then there are the wild cards in the deck: Could the LHC really create black holes or exotic forms of matter? What about all these claims that the world is in peril?
Tuesday: Doomsday fears and futuristic dreams
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