CPH Theory

For a research physicist, Sandra Ciocio knows all about the trials of the construction site. In recent years she’s seen 7,000 tons of sensitive equipment lowered down a 100-m shaft to prepare for a single grand experiment. The technology was groundbreaking and the schedule punishing. “It’s been deadline, deadline, deadline,” she says. “I haven’t had a holiday in five years.” But when the first real data begin to emerge this summer, the possible rewards should be worth the effort: a final explanation of one of the last puzzles of physics. “I feel like crying,” says Ciocio. “It’s like a dream come true.”

Deep beneath a tranquil patch of farmland, Ciocio and her colleagues at the European Organization for Nuclear Research, known as CERN, have built the world’s biggest and most sophisticated scientific instrument, the Large Hadron Collider, housed in a 27-kilometer tunnel that loops beneath the French-Swiss border. Using unprecedented energy, it will re-create the conditions a fraction of a millisecond after the big bang that gave birth to the cosmos 14 billion years ago. The goal: to track down a single elusive particle whose existence — if it can be proved — would fill a critical gap in our understanding of the universe.

This particular mystery has a daunting history. More than 30 years ago scientists developed an elegant series of equations, called the Standard Model, that describes the make-up of the universe in terms of the relationship between a few fundamental particles and forces. But the model has gaps. One gap is the baffling issue of mass. Why are some particles heavy while others have no mass at all? According to the leading theory, the weight of a particle depends on how it interacts with a mysterious “Higgs field” that permeates all space. So far scientists haven’t found any evidence that this field — and its associated particle, the Higgs boson — exists. They’ve been waiting for a particle collider big enough to perform the necessary experiments. The Large Hadron Collider was built to fit this bill.
The idea behind the collider is simple: get protons — positively charged particles present in every atom — going fast, crash them into each other and observe the fragments. The LHC will use superconducting magnets to guide the protons round and round the subterranean ring until they’re going almost as fast as light. The resulting collisions will release unprecedented amounts of energy (equivalent to 100,000 times the temperature at the center of the sun). With luck, they’ll also produce, among a shower of lesser particles, the long-sought Higgs boson.

The collider may also throw up clues to puzzles that arise at the strange intersection of particle physics and astronomy. To understand the cosmos, scientists must understand how it developed from those first primordial particles. “In effect, what we have is far and away the most capable microscope ever built, and the most powerful telescope ever built,” says theoretical physicist John Ellis. A central mystery is the supposed existence of invisible “dark matter,” and its counterpart “dark energy,” a strange force that seems to accelerate the expansion of the universe. Although together the dark pair make up for 96 percent of the universe, scientists know next to nothing about them — only their gravitational effects. Those grand collisions may produce undiscovered particles that account for both. The collider might also reveal yet another set of particles, the “superpartners,” needed to bolster the case for String Theory, a “theory of everything” that proposes the existence of six extra dimensions and a universe constructed of tiny vibrating strings.
All this knowledge comes with a whopping price tag: the collider will cost about euro 3 billion. Its annual energy consumption will match the entire city of Geneva’s. The 1 billion collisions taking place every second, captured and filtered by underground detectors, will generate enough data to fill 100,000 CDs a year. But ultimate knowledge is worth it, says CERN boss Robert Aymar.
It’s entirely possible that after all this money and effort the collider’s detectors will find no trace of the Higgs boson. That would still make the project worthwhile, researchers say. It would indicate beyond doubt that the Standard Model, the basis of modern physics, requires a radical rethinking. “Our theorist friends tell us to look this way or the other, but maybe Nature is telling us to look behind us,” says Tejinder Virdee, a physicist from Imperial College in London.
The Geneva experiments will keep scientists occupied for 20 years or more. “This is truly a once-in-a-generation experiment,” says Virdee, “but it will take a generation to do.” Setting up the world’s greatest experiment took more than a decade: fixing the nature of the cosmos will take a little longer.
-WILLIAM UNDERHILL (Newsweek)

Scientist Hope to Unlock Scientific Mysteries with World's Most Powerful Subatomic Collider

When the world's most powerful subatomic particle collider begins gathering data this summer, it will be a major milestone for a number ofUniversity of Washington scientists.

The UW, led by professors Henry Lubatti in physics and Colin Daly in mechanical engineering, played a central role in designing and fabricating nearly 90,000 tubes that are key to the workings of the Atlas detector. Atlas is one of six particle physics experiments that are part of the Large Hadron Collider at the European Organization for Nuclear Research, known as CERN, near Geneva, Switzerland.

Today, many high-energy physicists believe that they are continuing the same scientific thoughts that began over 2,000 years ago in ancient Greece. It was decided then that everything in the world must me made up of tiny indivisible things called atoms.

Only 100 years ago was the existence of atoms proven, but it wasn't until the 1930s when scientists were able to put down the basic equations of quantum mechanics, so that even the simplest atom - the Hydrogen atom - could be understood.

Now, physicists have not stopped looking deeper into the atom as the Large Hadron Collider (LHC), a particle accelerator, is being pieced together at CERN in Geneva and is due to be started up later this year.

"This is the greatest engineering feat of all mankind. It took the combined resources of nearly all of the countries in the world and thousand and thousands of scientists," said John Conway, UC Davis professor of physics and collaborator on the project. "People started designing this in the early 1990s and only now is it reaching completion."

A particle accelerator is a device used to study the nucleus, or center, of an atom. It is designed to take two beams of protons, accelerate them to extremely high energies, and then smash them together. By smashing the protons together, scientists hope to find smaller particles that have never been seen before.

These smaller particles are known as quarks, the fundamental building blocks of hadrons. Hadrons are subatomic particles such as protons and neutrons. In other words, quarks are fundamental building blocks of matter than makeup hadrons.

"When the electrons get shot inside the nucleus, they bounce out at very high angles sometimes, [showing that] there were smaller things still inside neutrons and protons, which we call quarks," Conway said.

At this point, there are six known types of quarks: up, down, charm, strange, top and bottom. Every proton, a type of hadron, for example, has three quarks inside of it: two up quarks and one down quark. Since an up quark has a charge of 2/3 and a down quark has a -1/3 charge, a proton would then contain a 1 charge.

Currently, the largest particle accelerator is the Tevatron at Fermilab, located near Chicago.

According to Robin Erbacher, a UC Davis associate professor of physics and member of the LHC team, the Tevatron collision energies are at about two tera-electron-volts (TeV), which is a trillion electron-volts. Comparatively, the LHC will eventually reach a collision energy of 14 TeV - seven times the energy of the Tevatron.

This means that the possibilities for discovering new particles and interactions are huge. The more energy the protons have in the accelerator, the more collision energy available to make new, heavy particles that have never been created on Earth before.

The LHC is 17 miles in circumference and about 100 meters underground, spanning the border between Switzerland and France. By comparison, the Tevatron is four miles around. Two beams of protons will travel in opposite directions inside the circular accelerator, gaining energy every time they go around.

According to the European Organization for Nuclear Research, physicists will use the LHC to recreate the conditions just after the Big Bang by colliding the two beams head-on at very high energy. Teams of physicists from around the world will analyze the particles created in the collisions using special detectors in a number of experiments dedicated to the LHC.

As the two protons go around the accelerator, they hit each other in the middle of the detector where a mini explosion occurs and hundreds of particles come out. The particles are surrounded with layers of different detectors, which can capture the particles that come out, and measure their energies and directions in the hope of reconstructing what happened when the two protons collided with each other.

One such detector is the Compact Muon Solenoid.

"The detector we built gives you the first information on the particles coming out of the collision, called a pixel detector," said Conway.

Conway relates the pixel detector to the pixels in a digital camera. The difference is that as detectors tell what particles are passing through, the pixels are larger than the ones in a camera, and the detector can take 40 million pictures per second.

A particle that the scientists at CERN hope to discover is the Higgs Boson. It is proposed that the Higgs Boson is how particles acquire different masses.

"If this theory is right with the new experiment at the LHC, we hope to answer the question: is there a Higgs Boson, and if so, what does it look like, is it one particle, or many?" Conway said.

The accelerator was built for discovery, and while theories of what will be discovered do exist, what will emerge from the device is not entirely known.

"In general, I would say it is too soon to tell how the LHC will benefit humankind," Erbacher said in e-mail interview. "We often don't know how our discoveries will help us in the future until we've made them. This is indeed a pure research science."

YASSMIN ATEFI can be reached at science@californiaaggie.com.XXX