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At Large Hadron Collider, scientists await highest-energy proton beam collision

The goal is to reproduce conditions that were present less than a billionth of a second after the Big Bang that created the universe, yielding particles including the elusive Higgs boson.

March 30, 2010|By Thomas H. Maugh II

Some time after midnight Monday Los Angeles time -- more than a year and a half later than originally projected -- researchers in Geneva were expected to begin smashing two proton beams together at the highest energies ever recorded. The effort is the world's largest, most expensive physics project to date.

Traveling around the $10-billion, nearly 17-mile-circumference Large Hadron Collider, the beams of protons will carry more than three times the energy of particles in the largest U.S. accelerator, previously the world's most powerful. Scientists hope the resulting collisions will provide new information about the events that occurred in the first fractions of a second after the so-called Big Bang that created the universe, as well as about the existence and identity of the dark matter that makes up the bulk of the universe.

Large Hadron Collider: An article in Tuesday's LATExtra section about the start-up of the Large Hadron Collider said that previous experiments with smaller accelerators had shown that protons and electrons were made of still smaller particles, such as quarks and gluons. Although protons are made of smaller particles, electrons are not. —

As the beams collide, they will reproduce conditions present less than a billionth of a second after the Big Bang, yielding showers of elementary particles, hopefully including some that scientists have never seen.

Previous experiments with smaller accelerators showed that protons and electrons were made of still smaller particles, such as quarks and gluons. At the higher energies available with the collider, physicists hope to see even smaller particles, perhaps even the elusive Higgs boson, which theorists believe provides the mass for other particles but which experimenters have never seen.

"This is the end of the beginning," said physicist Robert Cousins of UCLA, a lead researcher on one of the major experiments attached to the collider. "The real fun now will be making the physics measurements."

And no, the collisions will not create a massive black hole that will destroy the Earth. The headline-making furor over that near-impossibility has abated because the critics "have lost all credibility," Cousins said.

On Monday, as technicians at the collider underneath the Swiss-French border were finalizing their preparations, U.S. physicists at Caltech, the University of Florida and a score of universities in between began to gather around massive plasma screens to watch via the Internet.

The feat of colliding two proton beams circling the giant ring-shaped accelerator in opposite directions has been likened to firing needles across the Atlantic from opposite sides and getting them to collide midway.

Physicist Harvey Newman of Caltech was among those already watching technicians tune the accelerator beams. "We're very excited," he said. "This marks the opening of a whole new range of physics exploration."

But it may take hours or days for that first collision to occur. The last time the European Organization for Nuclear Research, or CERN, attempted collisions with a new accelerator, the Large Electron-Positron collider, in 1989, the first collision didn't happen for three days.

And even when collisions do begin, the output of data will be so massive -- picture the water running over Niagara Falls -- that mammoth computers will need months to sort through it looking for the extremely rare events that physicists hope to find.

Ten thousand people from 60 countries helped to design and build the massive collider, which was inaugurated with great ceremony in September 2008, only to be shut down almost immediately for repairs caused by an electrical short. A restart in April 2009 saw more problems, this time in the copper bus bars housing cables for the superconducting magnets that guide and accelerate the beams.

"This is by any measure one of the most complex instruments ever built," Newman said, so the problems were "not something unexpected."

For now, temporary fixes to the copper cables limit the energy of the circulating beams to 3.5 trillion electron volts (Tev), half the design capacity of 7 Tev.

Finally, late last year, the accelerator was up and running -- albeit far below its design capacity -- and, on Nov. 30, it achieved an energy of 1.18 Tev, surpassing the 0.98 Tev that can be achieved by Fermilab's Tevatron in Illinois. By the time the collider was switched off in mid-December, it had recorded collisions of 2.36 Tev, and data from those collisions are still being analyzed.

Beginning March 19, beams with an energy of 3.5 Tev began circulating in both directions in the collider, and it is those beams that technicians were to try to collide Tuesday, producing energies of 7 Tev.

The plan is for the collider to operate at those energies for nearly two years before it is shut down again to complete repairs on the copper bus bars. When it is restarted in 2013, researchers hope it will finally produce 7-Tev beams and 14-Tev collisions.


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