Research and Development on the Replacement ATLAS Tracker Required for a High Luminosity Upgrade to the LHC

This is a proposal to PPARC for a 3 year R&D programme aimed at answering key questions associated with the design of a replacement tracker for the ATLAS experiment at the Large Hadron Collider (LHC) at CERN. In order to increase further the ability of the LHC to discover and study fundamental physics at the smallest scales, it is proposed to extend LHC running and to greatly increase the collision rate after a long shutdown starting in 2014. To maintain the performance of ATLAS in this new phase of data-taking it will be necessary to replace the central component of the experiment which tracks the trajectories of charged particles produced in LHC collisions. This new 'tracker' will require novel technologies in order to withstand the much increased radiation flux associated with the greater collision rate and yet still measure the much larger numbers of charged particles per unit time with the same precision as will be obtained prior to the LHC upgrade. This project will develop these technologies and incorporate them into a layout for the replacement tracker which meets all the requirements imposed by physics performance, radiation tolerance and other constraints.