|First direct observation of jet quenching.|
At the recent seminar, the LHC’s dedicated heavy-ion experiment, ALICE, confirmed that QGP behaves like an ideal liquid, a phenomenon earlier observed at the US Brookhaven Laboratory’s RHIC facility. This question was indeed one of the main points of this first phase of data analysis, which also included the analysis of secondary particles produced in the lead-lead collisions. ALICE’s results already rule out many of the existing theoretical models describing the physics of heavy-ions.
After a very fast switchover from protons to lead ions, the LHC has achieved performances that allowed the machine to exceed both peak and integrated luminosity by a factor of three. Thanks to this, experiments have been able to produce high-profile results on ion physics almost immediately, confirming that the LHC was able to keep its promises for ions as well as for protons.A seminar on 2 December was the opportunity for the ALICE, ATLAS and CMS collaborations to present their first results on ion physics in front of a packed auditorium. These results are important and are already having a major impact on the understanding of the physics processes that involve the basic constituents of matter at high energies.In the ion-ion collisions, the temperature is so high that partons (quarks and gluons), which are usually constrained inside the nucleons, are deconfined to form a highly dense and hot soup known as quark-gluon plasma (QGP). This type of matter existed about 1 millionth of a second after the Big Bang. By studying it, scientists hope to understand the processes that led to the formation of nucleons, which in turn became the nuclei of atoms. See:LHC completes first heavy-ion run
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