The CMS Outer Tracker for the High Luminosity LHC upgrade

The High Luminosity Large Hadron Collider (HL-LHC) at CERN is expected to collide protons at a centre-of-mass energy of 14 TeV and to reach the unprecedented peak instantaneous luminosity of 5–7.5 $\times$ ${10}^{34}$ cm${}^{-2}$ s${}^{-1}$ with an average number of pileup events of 140–200. This will allow the ATLAS and CMS experiments to collect integrated luminosities up to 3000–4000 fb${}^{-1}$ during the project lifetime. To cope with this extreme scenario the CMS detector will be substantially upgraded before starting the HL-LHC, with a plan known as CMS Phase-2 upgrade. The CMS Tracker detector will have to be replaced in order to fully exploit the delivered luminosity and cope with the demanding operating conditions. The new detector will provide robust tracking as well as input for the first level trigger. This paper is focused on the replacement of the CMS Outer Tracker system, describing the new layout and the technological choices together with some highlights of module assembly and quality assurance aspects.