What major physics research facility at CERN, Switzerland, is scheduled to go on a 4-year break in July 2026 for significant upgrades?

The world's largest and most powerful particle accelerator, located at CERN in Switzerland, is scheduled for a significant four-year break beginning in July 2026. This major physics research facility will undergo extensive upgrades as part of the High-Luminosity Large Hadron Collider (HL-LHC) project. The aim of this ambitious undertaking is to dramatically enhance the accelerator's performance, preparing it for its next decade of scientific exploration.

The primary goal of the HL-LHC upgrade (Review) is to increase the machine's "luminosity" by a factor of ten compared to its original design. Luminosity is a crucial indicator of an accelerator's performance, directly proportional to the number of particle collisions that occur over a specific period. By boosting this rate, scientists will be able to collect a far greater amount of data, enabling them to study known phenomena, such as the Higgs boson, with unprecedented precision. It will also significantly improve the chances of observing extremely rare processes and potentially discovering new particles or forces that could extend our understanding beyond the Standard Model of particle physics.

This period, known as Long Shutdown 3 (LS3), involves replacing 1.2 kilometers of the LHC with innovative components and undertaking major transformations of its two general-purpose experiments, ATLAS and CMS, to prepare them for the staggering number of collisions. The upgrades are essential to push the boundaries of high-energy physics, allowing researchers to delve deeper into the fundamental building blocks of the universe. Operations with the upgraded High-Luminosity LHC are currently expected to resume in mid-2030, ushering in a new era of discoveries.