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LHC to stir up hot particle soup before 2013 shut down

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What happens when a proton smashes into a lead nucleus: a shower of particles through the CMS detector (Image: CERN)

What happens when a proton smashes into a lead nucleus: a shower of particles through the CMS detector (Image: CERN)

by Jacob Aron
At the foot of the misty mountains a mighty ring was forged – again! For one month, the Large Hadron Collider will smash two types of particles in a single magnetic ring.

So far, the LHC at CERN, near Geneva, Switzerland, has been colliding beams of identical types of particles, which are spun around the ring by a strong magnetic field. But starting in the third week of January it will smash protons into lead ions, in the hope of learning more about quark-gluon plasma. This is a hot soup of particles thought to make up the early universe.

Protons and lead ions have different masses and charges, so other colliders have used two magnetic rings to guide the beams. In the LHC, the beams will run in the same ring at slightly different speeds. “Nobody has ever run a collider quite like this before,” says CERN’s John Jowett.

Colour glass

Both beams circulate the LHC about 660,000 times a minute, but the proton beam goes slightly faster than the ion beam. “It’s as if you had a racetrack with a cyclist and a runner who have to bump into each other thousands of times at exactly four points,” says Paolo Giubellino of the ALICE experiment at CERN.

A successful test run last year has already thrown up surprises, including hints of a new form of matter known as colour-glass condensate. “It is an unexplained and very surprising feature and we very much wish to get more data to interpret it,” says Giubellino.

More data could help confirm the find, he says. The full-scale proton-lead ion runs will end in mid-February, when the collider shuts down for upgrades expected to last until late 2014

www.newscientist.com

Written by physicsgg

January 2, 2013 at 3:09 pm

Posted in High Energy Physics

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