The CMS Outer Tracker for the High Luminosity LHC

The High Luminosity LHC (HL-LHC) is expected to deliver an integrated luminosity of 3000 − 4000 fb − 1 in its lifetime with peak instantaneous luminosities reaching about 5 − 7 : 5 × 10 34 cm − 2 s − 1 . During the Long Shutdown 3 period, several components of the CMS detector will undergo major changes, called Phase-2 upgrades, to be able to operate in the challenging environment of the HL-LHC, including the replacement of the entire silicon tracker. The Phase-2 Outer Tracker (OT) will have high radiation tolerance, higher granularity, and the capability to handle higher data rates. Another key feature of the OT will be to provide tracking information to the Level-1 trigger, allowing trigger rates to be kept at a sustainable level without sacrificing physics potential. For this, the OT will be made of modules that have two closely spaced sensors read out by the same electronics, which can correlate hits in the two sensors creating short track segments called ”stubs”. The stubs will be used for tracking at 40 MHz. In this contribution, the design of the CMS Phase-2 OT, the technological choices, and highlights of research and development activities are reported.