The Large Hadron Collider (LHC) has completed proton run for 2015 and prepares for lead collisions

One of the first lead-lead collisions at the LHC, recorded by the ALICE detector in November 2010. Note the large number of particle tracks. Image credit: ALICE Collaboration
One of the first lead-lead collisions at the LHC, recorded by the ALICE detector in November 2010. Note the large number of particle tracks. Image credit: ALICE Collaboration

The Large Hadron Collider (LHC) has successfully completed its planned proton run for 2015, delivering the equivalent of about 400 trillion (1012) proton-proton collisions to both the ATLAS (A Toroidal LHC ApparatuS) and CMS (Compact Muon Solenoid) experiments. LHCb (Large Hadron Collider beauty) and ALICE (A Large Ion Collider Experiment) have also enjoyed successful data taking at lower collision rates.

CERN engineers will now prepare the accelerator to collide lead ions, for a physics run due to start in late November. These heavy-ion collisions allow physicists to investigate quark-gluon plasma, a state of matter thought to have formed just after the Big Bang.Of the seven experiments on the LHC ring, the 10,000 tonne ALICE detector is the most specialized for studying lead-lead collisions, in which the hundreds of protons and neutrons in two lead nuclei smash into one another at energies of upwards of a few trillion electronvolts each. This forms a miniscule fireball in which everything ‘melts’ into a quark-gluon plasma.

‘This new energy regime is of course very interesting for ALICE’, says ALICE spokesperson, Paolo Giubellino.

‘In this run we will also have much larger statistics to work with and our detector has been significantly upgraded since the LHC’s first run. So we now have a better instrument to study the system to a much higher precision and at even higher temperatures than during run 1!’, he added.

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