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Barish: Expect a Decade of Discovery from "Megascience" Particle Physics Projects

SAN DIEGO--Barry Barish studies particle physics, a science where researchers sometimes talk about the enormous strides they've made in the past two decades to draw closer to "a theory of everything." The discoveries have been significant, he said at the 2010 AAAS Annual Meeting, but "we're nowhere near the end of the field."

Massive projects, from a Antarctic "ice cube" laced with neutrino detectors to the headline-grabbing Large Hadron Collider particle accelerator, will make "the next decade or so really exciting" for particle physicists, said Barish.

Researchers have come to the point  "where we know how, but we don't what, we'll see," he said in his plenary speech on 22 February.

Barish directs the Global Design Effort for the International Linear Collider, a particle accelerator on the scale of the Large Hadron Collider. After receiving his Ph.D. in experimental high-energy physics from the University of California, Berkeley, in 1962, he participated in pioneering efforts to study particles in large underground laboratories around the world.

In its infancy, the mission of particle physics was to discover the building blocks of the universe. Physicists built increasingly bigger and faster accelerator laboratories to slam atoms together and watch them explode into their more basic components.

"It was an observational science in the same way that astronomy has been an observational science," said Barish.

The evidence for new particles--gluons, muons, strange and charmed quarks, to name a few--spilling out of the accelerators gave physicists a much richer picture of the physical world and the laws that govern it.

The discoveries moved the field toward "inquiry-based science," said Barish, where scientists are not ready yet to unveil complete theories, "but we now know some of the questions to ask."

The questions are numerous, and huge, he noted: What is the dark matter that is known only from its subtle gravitational tug on the visible universe? Are there extra dimensions beyond the four known on Earth? How many kinds of elemental particles exist? How did the universe come to be? Are there any undiscovered principles of nature?

Barish singled out neutrino research, particle astrophysics, and high energy colliders as research that could provide exciting results in the next decade.

Neutrinos are particles created by the fusion explosion of the sun. Each neutrino shifts between three "flavors," or types, as they stream through space, a fact that was only discovered in 1998. Once thought to be a particle with no mass, the new findings suggest neutrinos do have some mass after all.

Ongoing neutrino research in underground caves in Japan and deep below the Antarctic ice, said Barish, could help physicists decide whether neutrinos are contributing to the slight edge in matter compared to antimatter in the universe.

Particle physicists are collaborating with astrophysics colleagues to discover the composition of dark matter, which together with dark energy makes up nearly 95% of the universe.

Barish said the theory of supersymmetry may "provide particles that are natural candidates for dark matter." Supersymmetry suggests that all the known particles have a mirror set of heavier particles that have not yet been detected. Research published this month in the journal Science is a tantalizing hint that dark matter may soon be detectable, he suggested.

Physicists never really "see" particles; they detect them through a variety of data like the size and shape of the paths they travel, the radiation they emit, and the energy they lose when they collide with other particles. Like a snail's trail or footprints in the snow, physicists know particles by their traces.

But it takes "megascience projects" like the Large Hadron Collider and the planned International Linear Collider to capture these subtle signs. Inside the Hadron collider, protons could smash together every 25 nanoseconds, said Barish, which adds up to a massive amount of data to detect and analyze.

Researchers hope that the Hadron collider, which has suffered technical breakdowns since its launch in 2008 and is expected to run at half-power for the next year and a half, will uncover elusive particles like the predicted Higgs boson, which may interact with all other particles to give them mass.

"We've been very fortunate in what's been seen in the last 10 or 20 years," said Barish, who expects the exciting discoveries to continue and maybe push the field a little closer to that elusive theory of everything.

But it's also possible that in a decade, he says, "we'll find that these ideas will be stale and maybe wrong."