First Collisions for the LHC

by Nancy Atkinson on November 23, 2009

Screens showing two beams in the LHC.  Credit: CERN

Screens showing two beams in the LHC. Credit: CERN

Two beams circulated simultaneously inside the Large Hadron Collider for the first time today, allowing for the first proton-proton collisions to take place. “It’s a great achievement to have come this far in so short a time,” said CERN Director General Rolf Heuer. “But we need to keep a sense of perspective – there’s still much to do before we can start the LHC physics program.”

The beams crossed at points where various detectors are stationed. The beams were made to cross at point 1, where the ATLAS all purpose detector is located, then at point five at the CMS (Compact Muon Solenoid) detector. Later, beams crossed at points 2 and 8, where the ALICE (heavy ion detector) and the LHCb (looking for heavy particles containing a bottom quark) are positioned.

The first collisions are allowing operators to test the synchronization of the beams.

“This is great news, the start of a fantastic era of physics and hopefully discoveries after 20 years’ work by the international community to build a machine and detectors of unprecedented complexity and performance,” said ATLAS spokesperson, Fabiola Gianotti at a press conference today.

“The events so far mark the start of the second half of this incredible voyage of discovery of the secrets of nature,” said CMS spokesperson Tejinder Virdee.

“It was standing room only in the ALICE control room and cheers erupted with the first collisions” said ALICE spokesperson Jurgen Schukraft. “This is simply tremendous.”

“The tracks we’re seeing are beautiful,” said LHCb spokesperson Andrei Golutvin, “we’re all ready for serious data taking in a few days time.”

The first collisions come just three days after the LHC restart. Since the start-up this weekend, the operators have been circulating beams around the ring alternately in one direction and then the other at the injection energy of 450 GeV (gigaelectron volts). 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. If everything goes as planned, everyone at CERN hopes to obtain good quantities of collision data for all the experiments’ calibrations by Christmas, when the LHC should reach 1.2 TeV (terraelectron volts) per beam.

Source: CERN

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Nancy Atkinson is Universe Today's Senior Editor. She also works with Astronomy Cast, and is a NASA/JPL Solar System Ambassador.

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