LHC : beams are back

[**After 3 years of technical shutdown, the beams are back in the LHC!
*]

This Tuesday, October 26, 2021, at 12:40, CMS again recorded proton collisions. This success is the result of intense preparation of the detector and its acquisition system during this technical shutdown.

The commissioning effort intensified during the summer of 2021 with continuous cosmic data collection. The LLR CMS team is responsible for the triggering system that captured these very early events! This system designed by the LLR is once again ready for operation during the entire period of Run-3. In order to be functional and above all effective in an ever more intense hadronic environment, the triggering system will have required several optimizations, such as the configuration parameters of the algorithms in order to preserve an adequate selection threshold for the physics program.

The LLR teams on site are also responsible for monitoring correct operation at all times and ensuring permanent on-call duty with the detector. At the same time, the CMS team at the LLR will have used this technical shutdown to finalize major data analyzes, some of which have reported sightings in the Higgs boson area. More than ever, the team is ready to conduct these analyzes with the new data and contribute to advancements in the field. These advances require new technologies in order to always push our ability to reconstruct and identify rare physical processes even further. The LLR has a central role in the pioneering developments in calorimetry with the HGCAL project and the trigger system with the L1 Trigger Upgrade project.

Prototype tests of these systems are underway with a view to their installation at the next technical shutdown in 2025, and their commissioning in 2027 for Run 4.

Contact : Alexandre Zabi