The Phase-2 upgrade of the CMS Outer Tracker

The Large Hadron Collider at CERN will undergo a major upgrade in the Long Shutdown 3 from 2025-2027. The so-called High Luminosity LHC (HL-LHC) is expected to deliver peak instantaneous luminosities of about $5-7.5\times10^{34}$cm$^{-2}$s$^{-1}$ and an integrated luminosity of about $3000-4500\;$fb$^{-1}$ during ten years of operation. In order to fully exploit the delivered luminosity and to cope with the demanding operating conditions, the entire silicon tracking system of the CMS experiment will have to be replaced. The Phase-2 Outer Tracker (OT) will have an increased radiation hardness, a higher granularity, and will be able to cope with larger data rates. In addition, the OT will provide tracking information to the Level-1 trigger. To achieve this, each module will consist of two closely spaced sensors. The readout chips use hit information of both sensors for a rough transverse momentum measurement. This novel concept will improve the selection performance of the trigger under large pileup conditions. Furthermore, the Phase-2 OT will use evaporative CO$_{2}$ cooling and a DC-DC conversion based powering scheme to keep the material budget small. In this report, the design of the CMS Phase-2 Outer Tracker and the present status of the project will be presented.