First collisions observed in the Large Hadron Collider

November 24, 2009

The first proton-proton collisions have been observed in the Large Hadron Collider (LHC) located at the CERN laboratory in Geneva, Switzerland. Groups at BU have been deeply involved in the two large LHC experiments ATLAS and CMS since the mid-1990’s.

From today’s CERN press release:

“Geneva, 23 November 2009. Today the LHC circulated two beams simultaneously for the first time, allowing the operators to test the synchronization of the beams and giving the experiments their first chance to look for proton-proton collisions. With just one bunch of particles circulating in each direction, the beams can be made to cross in up to two places in the ring. From early in the afternoon, the beams were made to cross at points 1 and 5, home to the ATLAS and CMS detectors, both of which were on the lookout for collisions. Later, beams crossed at points 2 and 8, ALICE and LHCb.
These developments come just three days after the LHC restart, demonstrating the excellent performance of the beam control system. Since the start-up, the operators have been circulating beams around the ring alternately in one direction and then the other at the injection energy of 450 GeV. The beam lifetime has gradually been increased to 10 hours, and today beams have been circulating simultaneously in both directions, still at the injection energy.
Next on the schedule is an intense commissioning phase aimed at increasing the beam intensity and accelerating the beams. All being well, by Christmas, the LHC should reach 1.2 TeV per beam, and have provided good quantities of collision data for the experiments’ calibrations.”

For the complete press release, click here. For event displays and movies of the first events observed by ATLAS and CMS, go to:

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