Somebody posted this (the CERN project) in another forum:
May 15, 2007
A Giant Takes On Physics Biggest Questions
By DENNIS OVERBYE
Correction Appended
300 FEET BELOW MEYRIN, Switzerland The first thing that gets you is the noise.
Physics, after all, is supposed to be a cerebral pursuit. But this cavern almost measureless to the eye, stuffed as it is with an Eiffel Towers worth of metal, eight-story wheels of gold fan-shape boxes, thousands of miles of wire and fat ductlike coils, echoes with the shriek of power tools, the whine of pumps and cranes, beeps and clanks from wrenches, hammers, screwdrivers and the occasional falling bolt. It seems no place for the studious.
The physicists, wearing hardhats, kneepads and safety harnesses, are scrambling like Spiderman over this assembly, appropriately named Atlas, ducking under waterfalls of cables and tubes and crawling into hidden room-size cavities stuffed with electronics.
They are getting ready to see the universe born again.
Again and again and again 30 million times a second, in fact.
Starting sometime next summer if all goes to plan, subatomic particles will begin shooting around a 17-mile underground ring stretching from the European Center for Nuclear Research, or Cern, near Geneva, into France and back again luckily without having to submit to customs inspections.
Crashing together in the bowels of Atlas and similar contraptions spaced around the ring, the particles will produce tiny fireballs of primordial energy, recreating conditions that last prevailed when the universe was less than a trillionth of a second old.
Whatever forms of matter and whatever laws and forces held sway Back Then relics not seen in this part of space since the universe cooled 14 billion years ago will spring fleetingly to life, over and over again in all their possible variations, as if the universe were enacting its own version of the Groundhog Day movie. If all goes well, they will leave their footprints in mountains of hardware and computer memory.
We are now on the endgame, said Lyn Evans, of Cern, who has been in charge of the Large Hadron Collider, as it is called, since its inception. Call it the Hubble Telescope of Inner Space. Everything about the collider sounds, well, large from the 14 trillion electron volts of energy with which it will smash together protons, its cast of thousands and the $8 billion it cost to build, to the 128 tons of liquid helium needed to cool the superconducting magnets that keep the particles whizzing around their track and the three million DVDs worth of data it will spew forth every year.
The day it turns on will be a moment of truth for Cern, which has spent 13 years building the collider, and for the worlds physicists, who have staked their credibility and their careers, not to mention all those billions of dollars, on the conviction that they are within touching distance of fundamental discoveries about the universe. If they fail to see something new, experts agree, it could be a long time, if ever, before giant particle accelerators are built on Earth again, ringing down the curtain on at least one aspect of the age-old quest to understand what the world is made of and how it works.
If you see nothing, said a Cern physicist, John Ellis, in some sense then, we theorists have been talking rubbish for the last 35 years.
Fabiola Gianotti, a Cern physicist and the deputy spokeswoman for the team that built the Atlas, said, Something must happen.
The accelerator, Dr. Gianotti explained, would take physics into a realm of energy and time where the current reigning theories simply do not apply, corresponding to an era when cosmologists think that the universe was still differentiating itself, evolving from a primordial blandness and endless potential into the forces and particles that constitute modern reality.
She listed possible discoveries like a mysterious particle called the Higgs that is thought to endow other particles with mass, new forms of matter that explain the mysterious dark matter waddling the cosmos and even new dimensions of spacetime.
For me, Dr. Gianotti said, it would be a dream if, finally, in a couple of years in a laboratory we are going to produce the particle responsible for 25 percent of the universe.
Halfway around the ring stood her rival of sorts, Jim Virdee from Imperial College London, wearing a hardhat at the bottom of another huge cavern. Dr. Virdee is the spokesman, which is physics-speak for leader, of another team, some 2,500 strong, with another giant detector, the poetically named Compact Muon Detector, which was looming over his shoulder like a giant cannon.
The prospect of discovery, Dr. Virdee said, is what sustained him and his colleagues over the 16 years it took to develop their machine. Without such detectors, he said, this field which began with Newton just stops.
When we started, we did not know how to do this experiment and did not know if it would work, he said. Twenty-five hundred scientists can work together. Our judge is not God or governments, but nature. If we make a mistake, nature will not hesitate to punish us.
Game of Cosmic Leapfrog
The advent of the Cern collider also cements a shift in the balance of physics power away from American dominance that began in 1993, when Congress canceled the Superconducting Supercollider, a monster machine under construction in Waxahachie, Tex. The supercollider, the most powerful ever envisioned, would have sped protons around a 54-mile racetrack before slamming them together with 40 trillion electron volts.
For decades before that, physicists in the United States and Europe had leapfrogged one another with bigger, more expensive and, inevitably, fewer of these machines, which get their magic from Einsteins equation of mass and energy. The more energy that these machines can pack into their little fireballs, the farther back in time they can go, closer and closer to the Big Bang, the smaller and smaller things they can see.Recalling those times, Dr. Evans said: There was a nice equilibrium across the Atlantic. People used to come and go.
Now, Dr. Evans said, The center of gravity has moved to Cern.
The most powerful accelerator now operating is the trillion-electron volt Tevatron, colliding protons and their antimatter opposites, antiprotons, at the Fermi National Accelerator Laboratory in Batavia, Ill. But it is scheduled to shut down by 2010,
Cern was born amid vineyards and farmland in the countryside outside Geneva in 1954 out of the rubble of postwar Europe. It had a twofold mission of rebuilding European science and of having European countries work together.
Today, it has 20 countries as members. Yearly contributions are determined according to members domestic economies, and a result is a stable annual budget of about a billion Swiss francs. The vineyards and cows are still there, but so are strip malls and shopping centers.
It was here that the World Wide Web was born in the early 1990s, but the director-general of Cern, Robert Aymar, joked that the labs greatest fame was as a locus of conspiracy in the novel Angels and Demons, by the author of The DaVinci Code, Dan Brown. The lab came into its own scientifically in the early 80s, when Carlo Rubbia and Simon van der Meer won the Nobel Prize by colliding protons and antiprotons there to produce the particles known as the W and Z bosons, which are responsible for the so-called weak nuclear force that causes some radioactive decays.
Bosons are bits of energy, or quanta, that, according to the weird house rules of the subatomic world, transmit forces as they are tossed back and forth in a sort of game of catch between matter particles. The Ws and Zs are closely related to photons, which transmit electromagnetic forces, or light.
The lab followed up that triumph by building a 17-mile-long ring, the Large Electron-Positron collider, or Lep, to manufacture W and Z particles for further study. Meanwhile, the United States abandoned plans for an accelerator named Isabelle to leapfrog to the giant supercollider in Texas.
Even before that supercollider was canceled, in 1993, however, Cern physicists had been mulling building their own giant proton collider in the Lep tunnel.
In 1994, after the supercollider collapse gave its own collider a clear field, the Cern governing council gave its approval. The United States eventually agreed to chip in $531 million for the project. Cernalso arranged to borrow about $400 million from the European Investment Bank. Even so, there was a crisis in 2001 when the project was found to be 18 percent over budget, necessitating cutting other programs at the lab. The colliders name comes from the word hadron, which denotes subatomic particles like protons and neutrons that feel the strong nuclear force that binds atomic nuclei.
Whether the Europeans would have gone ahead if the United States had still been in the game depends on whom you ask. Dr. Aymar, who was not there in the 90s, said there was no guarantee then that the United States would succeed even if it did proceed.
Certainly in Europe the situation of Cern is such that we appreciate competition, he said. But we assume we are the leader and we have all intention to remain the leader. And well do everything which is needed to remain the leader.
To match the American machine, however, the Europeans, with a much smaller tunnel 17 miles instead of 54 had to adopt a riskier design, in particular by doubling the strength of their magnets.
In this business, society is prepared to support particle physics at a certain level, Dr. Evans saids. If you want society to accept this work which is not cheap, you have to be really innovative.
Cocktail Party Physics
The payoff for this investment, physicists say, could be a new understanding of one of the most fundamental of aspects of reality, namely the nature of mass.
This is where the shadowy particle known as the Higgs boson, a k a the God particle, comes in.
In the Standard Model, a suite of equations describing all the forces but gravity, which has held sway as the law of the cosmos for the last 35 years, elementary particles are born in the Big Bang without mass, sort of like Adam and Eve being born without sin.
Some of them (the particles, that is) acquire their heft, so the story goes, by wading through a sort of molasses that pervades all of space. The Higgs process, named after Peter Higgs, a Scottish physicist who first showed how this could work in 1964, has been compared to a cocktail party where particles gather their masses by interaction. The more they interact, the more mass they gain.
The Higgs idea is crucial to a theory that electromagnetism and the weak force are separate manifestations of a single so-called electroweak force. It shows how the massless bits of light called photons could be long-lost brothers to the heavy W and Z bosons, which would gain large masses from such cocktail party interactions as the universe cooled.
The confirmation of the theory by the Nobel-winning work at Cern 20 years ago ignited hopes among physicists that they could eventually unite the rest of the forces of nature.
Moreover, Higgs-like fields have been proposed as the source of an enormous burst of expansion, known as inflation, early in the universe, and, possibly, as the secret of the dark energy that now seems to be speeding up the expansion of the universe. So it is important to know whether the theory works and, if not, to find out what does endow the universe with mass.
But nobody has ever seen a Higgs boson, the particle that personifies this molasses. It should be producible in particle accelerators, but nature has given confusing clues about where to look for it. Measurements of other exotic particles suggest that the Higgss mass should be around 90 billion electron volts, the unit of choice in particle physics. But other results, from the Lep collider here before it shut down in 2000, indicate that the Higgs must weigh more than 114 billion electron volts. By comparison, an electron is half a million electron volts, and a proton is about 2,000 times heavier.
Weve nearly ruled out the Standard Model, if you want to say it that way, said John Conway, a Fermilab physicist. The new collider was specifically designed to hunt for the Higgs particle, which is key both to the Standard Model and to any greater theory that would supersede it.
Theorists say the Higgs or something like it has to show up simply because the Standard Model breaks down and goes kerflooey at energies exceeding one trillion electron volts. If you try to predict what happens when two particles collide, it gives nonsense, explained Dr. Ellis of Cern, a senior theorist with the long white hair and a bushy beard to prove it.
There is either a violation of probability or some new physics, Dr. Ellis said.
Nima Arkani-Hamed of Harvard said he would bet a years salary on the Higgs.
If the Higgs or something like it doesnt exist, Dr. Arkani-Hamed said, then some very basic things like quantum mechanics are wrong.
A result, Dr. Gianotti said, is either we find the Higgs boson, or some stranger phenomenon must happen.
Nightmares
If the Cern experimenters find the Higgs, Nobel Prizes will flow like water. But just finding the elusive particle will not be enough to satisfy the theorists, who profess to be haunted by a much deeper problem, namely why the putative particle is not millions of times heavier than it appears to be.
When they try to calculate the mass of the Higgs particle using the Standard Model and quantum mechanics, they get what Dr. Ellis called a very infinite answer.
Rather than a trillion electron volts or so, quantum effects push the mass all the way up to 10 quadrillion trillion electron volts, known as the Planck energy, where gravity and the other particle forces are equal.
The culprit is quantum weirdness, one principle of which is that anything that is not forbidden will happen. That means the Higgs calculation must include the effects of its interactions with all other known particles, including so-called virtual particles that can wink in and out of existence, which shift its mass off the scale.
As a result, if the Standard Model is valid for all energies, said Joe Lykken, a Fermilab theorist, then you are in deep doodoo trying to explain why the Higgs mass isnt a quadrillion times bigger than it needs to be.
Another way to put it is to ask why gravity is so much weaker than the other forces the theory wants them all to be equal.
Theorists can rig their calculations to have the numbers come out right, but it feels like cheating. What we have to do to equations is crazy, Dr. Arkani-Hamed said.
One solution that has been proposed is a new principle of nature called supersymmetry that, if true, would be a bonanza for the Cern collider.
It posits a relation between the particles of matter like electrons and quarks and particles that transmit forces like photons and the W boson. For each particle in one category, there is an as-yet-undiscovered superpartner in the other category.
Supersymmetry doubles the world, Dr. Arkani-Hamed said.
These superpartners cancel out all the quantum effects that make the Higgs mass skyrocket. Supersymmetry is the only known way to manage this, Dr. Lykken said.
Because Higgs bosons are expected to be produced very rarely, it could take at least a year or more for physicists to confirm their discovery at the collider. But some supersymmetric particles, if they exist, should be produced abundantly and could thus pop out of the data much sooner. Suppose a gluino exists at 300 billion electron volts, Dr. Arkani-Hamed said, referring to a putative superpartner. We could know the first day if they exist.
For several years, supersymmetry has been a sort of best bet to be the next step beyond the Standard Model, which is undefeated in experiments but has enormous gaps. The Standard Model does not include gravity or explain why, for example, the universe is matter instead of antimatter or even why particles have the masses they do.
In the end, Michelangelo Mangano, a theorist at Cern, said, The standard model prediction cant be the end of the story.
Supersymmetry also fixes a glitch in the age-old dream of explaining all the forces of nature as manifestations of one primordial force. It predicts that at a high enough energy, all the forces electromagnetic, strong and weak have identical strengths.
If supersymmetry is right, unification works, Dr. Ellis said.
But there is no direct evidence for any of the thousands of versions of supersymmetry that have been proposed. Indeed, many theorists are troubled that its effects have not already shown up in precision measurements at accelerators.
It doesnt smell good, Dr. Arkani-Hamed said. Physicists say the best indirect evidence for supersymmetry comes from the skies, where the galaxies have been found to be swaddled by clouds of invisible dark matter, presumably unknown particles left over from the Big Bang. Dark matter is a very physical argument. Dr. Ellis said. If you take astrophysics seriously, there has to be some unseen stuff out there.
On the menu of discoveries, there is always None of the Above. As Dr. Gianotti put it: Nature has chosen another solution. This will be great.