From CERN: “ALICE through a gamma-ray looking glass”

CERN New Masthead

31 July 2013
Christine Sutton

“The ALICE experiment at CERN specializes in heavy-ion collisions at the LHC, which can produce thousands of particles. In analysing this maelstrom, the researchers need to know exactly how material is distributed in the detector – and it turns out that the LHC’s simpler proton–proton collisions can help.

layers
A gamma-ray view of the layers of the ALICE detector. (Image: ALICE)

Gamma-rays produced in the proton–proton collisions, mainly from the decays of neutral pions, convert into pairs of electrons and positrons as they fly through matter in the detector. The origin of these pairs can be accurately detected, providing a precise 3D image that includes even the inaccessible innermost parts of the experiment. The process is almost exactly the same as in 1895 when Wilhelm Röntgen produced an X-ray image of his wife’s hand – the inner parts of the body could be seen for the first time without surgery. The main difference lies in the energy of the radiation – ten times greater for the gamma rays in ALICE than for Röntgen’s X-rays. Importantly for the ALICE experiment, it allows the team to check crucial simulations.”

See the full article here.

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