Particles finally come together with a bang

The Large Hadron Collider, the world’s biggest and most expensive science experiment, produced its first collisions, said scientists at CERN, the European Organization for Nuclear Research, outside Geneva. Seemingly making up for lost time after years of disasters and delays, the collisions came only three days after engineers had begun shooting the subatomic particles known as protons around their 17-mile underground racetrack. The physicists announced that they had succeeded in making the beams collide, producing what they called “candidate collision events” in the giant particle detectors in the collider.

The collider has been built over 15 years at a cost of $9 billion to accelerate protons to energies of seven trillion electron volts apiece and then slam them together in an attempt to recreate forces and particles that reigned during the first moments of the Big Bang. But for much of that time, the only things that have gone bang in the collider were magnets and other components, most notably in September 2008 after the first time protons circled the collider.

When the beams began circulating again on November 20, CERN officials said they expected the first collisions to happen in early December.

“It’s a great achievement to have come this far in so short a time,” CERN’s director general, Rolf Heuer, said in a news release. “But we need to keep a sense of perspective — there’s still much to do before we can start the L.H.C. physics program.”

In the control rooms of the collider and of the four giant particle detectors, built and staffed by thousands of physicists who have the job of interpreting the data from the beginning of time, there were cheers and Champagne.

Michael Tuts of Columbia University said he and his colleagues were “ecstatic at the news.” But the most important scientific results from the collider are still far in the future, scientists said.

The collisions were basically a test of the collider systemsÂ’ ability to synchronize the beams, in which bunches of protons travel along at nearly the speed of light, and make them collide at the right points. The protons were at their so-called injection energies of 450 billion electron volts, a far cry from the energies the machine will eventually achieve.

In the next weeks before a holiday break, CERN hopes to increase the proton energies to 1.2 trillion electron volts apiece, which would make the hadron collider officially the most powerful in the world, eclipsing the Tevatron (900 billion electron volts) at Fermilab in Illinois.

Early next year the first runs devoted to physics research will start at 3.5 trillion electron volts — half the original design energy. To get near 7 trillion electron volts, the engineers say, the machine will have to be shut down a year from now for a lengthy period of repairs and other work.