The tracking system for the IDEA detector at future lepton colliders

While most requirements for detectors at the International Linear Collider (ILC) are very similar to those for the future circular e+e−-colliders FCC–ee (e+e− Future Circular Collider at CERN) or CEPC (Circular Electron–Positron Collider at IHEP, China), the luminosity is expected to be one or two orders of magnitude larger, with a much shorter bunch spacing, placing severe constraints on the tracking system, favouring an intrinsically fast main tracker to fully exploit the cleanliness of the e+e− environment. Moreover, limits on the maximum magnetic field of the tracker solenoid represent a problem for a large volume TPC, because of the resolution degradation, and for a Si tracker, since it would require a larger radius. The proposed ultra-light He based Drift Chamber is 4m long, starting at a radius of ∼30cm and extending up to 2m, with ≲1.5cm drift cells, arranged in a fully stereo configuration ((50–250)mrad) and instrumented with readout electronics implementing the Cluster Counting/Timing technique. The total material budget is approximately 0.016X0 for tracks in the barrel region and 0.05X0 for forward tracks, providing a momentum resolution of ∼5×10−4 for <10GeV∕c and of <4×10−3 for 100GeV∕c tracks. Moreover, the use of the Cluster Counting technique will allow for a particle identification (PID) resolution <3%, a factor two better than the resolution attainable with dE/dx technique. We will illustrate the tracking system performance obtained with detailed simulations. The hardware features and the construction procedures of the proposed Drift Chamber, making use of the assembly technique developed for MEG2, will also be presented.