First major structure of the future CMS tracker arrives at CERN

Major component of future CMS tracker reaches CERN

4 August 2026

The cornerstone mechanical element of the upcoming CMS tracker has arrived at the European Organization for Nuclear Research (CERN) facility. This is a vital step as preparations advance for the High-Luminosity LHC (HiLumi LHC), which will require an upgraded detector to handle the increased collision rates anticipated at the HiLumi LHC.

The Tracker Barrel 2S (TB2S) wheel, a 2.3-meter-long structure, forms the outer mechanical framework of the CMS detector's future tracker. Constructed and assembled by teams from the IPHC (CNRS/University of Strasbourg) in France, the TB2S wheel is built from lightweight carbon-fibre composite materials. This combination provides the high mechanical precision required, while also offering sufficient strength to support hundreds of kilograms of detector components.

From 2027 onward, the TB2S wheel will host more than 4,000 2S-type silicon sensor modules. Each module consists of two silicon microstrip sensors separated by 1.8 millimeters. Work on the TB2S wheel began in 2017 and culminated in its transport to CERN in July, encased in a specially designed container. Following this arrival, the structure will undergo additional measurements before the integration of the silicon modules.

This major infrastructure piece will serve as the backbone of the new CMS tracker, enabling the experiment to capture the vast amounts of data generated during the HiLumi LHC era.