Upgrades of the Tracker and Trigger of the CMS experiment at the CERN LHC

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To allow deeper investigations of the physics of discoveries expected at the LHC, and the challenges presented by the very successful performance of the accelerator, upgrades to some key CMS sub-systems are required in the next few years. In addition, LHC operation is expected to continue for at least a decade longer than the experiments were designed for. Inevitable radiation damage to the tracking detector will require its replacement in 2022 and the new detector must be more granular and radiation hard. It must also perform better in an even harsher environment, with higher pileup of events in each beam crossing, to meet the required physics goals.The LHC, which is the highest energy machine in the world, is the only accelerator capable of investigating some of the highest priority fundamental physics topics for the foreseeable future. In addition to the hoped for completion of the Standard Model by the discovery of the Higgs boson, it allows us to shed light on many other key questions in particle physics including the nature of dark matter, unification of forces, the existence of fundamental particles and their roles in the origin of the universe. The investment in the LHC programme has been significant and upgrades to the experiments will extend its working lifetime considerably, and improve their performance by taking advantage of technological progress in the last decade.The most crucial sub-detectors to be modified are the tracker and trigger, in which UK groups have played significant roles and have undertaken successful R&D in recent years. We propose to build on this by delivering a significant part of the new calorimeter trigger system and continuing R&D to incorporate tracking data into the future Level 1 trigger. We will deliver a new data acquisition system for the new pixel detector, and contribute to construction of detector modules for the future tracker by providing major parts of the front end electronics. In each case, the UK will be providing hardware, firmware and software with substantial intellectual input and leadership roles.These represent substantial contributions to the overall CMS upgrade plan consistent with proportionate sharing of construction responsibilities. We request appropriate resources to allow us to undertake these projects.