First lead-ion collisions in the Large Hadron Collider at record energy

November 18, a test using collisions of lead ion Colliders was carried out in the Large Hadron and provided an opportunity for the experiments to validate the new detectors and data-processing systems

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After the successful start of Run 3 in July this year, which featured protons-proton collisions at the record energy of 13.6 TeV, it was the turn of lead nuclei to circulate in the LHC again last Friday after four years

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A state of matter in which the elementary constituents, quarks and gluons, are not confined within nucleons but can move and interact is being studied by lead.

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This is an essential step in preparation for the physics runs with lead-lead crashes that are planned for the following years of Run 3 and Run 4. Each of the 208 nucleons of one lead nuclei can interact with one or several of the other lead nuclei

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Improvements have been made to the ion injector complex in order to double the intensity of the lead-ion beams for the High-Luminosity LHC

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In order to achieve this goal, a technique called "momentum slip-stacking" is needed, where two batches of four lead-ion bunches are separated by 100 milliseconds.

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the total number of bunches injected into the LHC to increase, from 648 in Run 2 to 1248 in Run 3 and onwards. The number of heavy ion collisions with respect to the past runs will be ten times higher after all the upgrades have been completed

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The test was important for ALICE, the experiment that focuses on the study of lead-ion collisions

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The new detectors give a higher spatial resolution for reconstructing the trajectory and properties of the particles produced in the collisions

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the upgraded apparatus and upgraded processing chain can record the full collision information at a rate two orders of magnitude higher.

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The new heavy-ion environment of higher energy and 50ns bunch spacing made it necessary for other experiments to commission their upgraded and newly installed subsystems

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The upgrade to the selected software is designed to improve the heavy-ion-physics data that is taken in Run 3. A new particle-track Trigger designed to spot a wider range of "ultra-peripheral collisions" was tested by physicists

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In order to take full advantage of the high-energy lead-lead collisions, several components of its readout, data acquisition, trigger, and reconstruction chains have been upgraded

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In the challenging conditions of lead-lead collisions characterized by a very large particle multiplicity, the brand-new detector was commissioned

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The new SMOG2 system, which is unique to the experiment and is designed to inject noble gases into the collision area, was used to collect lead-argon collisions in fixed-target mode

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