The primary physics goal is the study of the elusive state of matter known as Quark-Gluon Plasma (QGP)
The first long heavy-ion data taking of Run 3 has started: on Tuesday, September 26th around 20:00, first stable beams of the lead run were declared [1] and the 4 experiments were able to immediately start recording collisions. Compared to Run2, the lead nuclei are colliding with an increased energy of 5.36 TeV per nucleon pair (compared to 5.02 TeV previously) and the collision rate has increased by a factor of 10. The primary physics goal of this run is the study of the elusive state of matter known as Quark-Gluon Plasma (QGP), that is believed to have filled the Universe up to a millionth of a second after the Big Bang. It can be recreated in the laboratory in heavy-ion collisions and the ongoing heavy-ion run is expected to bring significant advances in our understanding of Quark-Gluon Plasma.
In addition to the improved parameters of the lead-ion beams, significant upgrades have been performed in the experiments that detect and analyse the collisions. ALICE, the LHC experiment which primarily focuses on studies of quark-gluon plasma, is now using an entirely new mode of data taking, storing all collisions without selection, resulting in up to 100 times more collisions being recorded per second. In addition, its track reconstruction efficiency and precision have increased due to the installation of new detectors and upgrades of existing ones. The ALICE Trieste group, comprised of 10 dedicated researchers from the Department of Physics and the National Institute of Nuclear Physics, played a crucial role in the development and construction of the cutting-edge Inner Tracking System 2 (ITS2). This innovative tracking system is exclusively built upon silicon sensors utilizing active monolithic pixels (MAPS) and covering an impressive area of 10m^2. Remarkably, it boasts 12.5 billion pixels, each measuring less than 30 µm on every side. Members of the group are currently engaged in the operations and the data quality control for this novel detector.
[1] https://home.cern/news/news/experiments/lhc-lead-ion-collision-run-starts
