Tracking and vertex detectors at FCC-ee

Abstract

AbstractThe combined vertexing and tracking performance of the innermost part of the FCC-ee experiments must deliver outstanding precision for measurement of the track momentum together with an impact parameter resolution exceeding by at least a factor five that typically achieved at LHC experiments. Furthermore, precision measurements require stability and fiducial accuracy at a level which is unprecedented in collider experiments. For the innermost vertex layers these goals translate into a target hit resolution of approximately 3 $$\mu \hbox {m}$$ μ m together with a material budget of around 0.2% of a radiation length per layer. Typically this performance might be provided by silicon-based tracking, together with a careful choice of a low-mass cooling technology, and a stable, low-mass mechanical structure capable of providing measurements with a low enough systematic error to match the tremendous statistics expected, particularly for the run around the Z resonance. At FCC-ee, the magnetic field will be limited to approximately 2 T, in order to contain the vertical emittance at the Z pole, and a tracking volume up to relative large radius is needed. The technological solution could be silicon- or gaseous-based tracking, in both cases with the focus on optimising the material budget, and particle identification capability would be an advantage. Depending on the global design, an additional silicon tracking layer could be added at the outer radius of the tracker to provide a final precise point contributing to the momentum or possibly time-of-flight measurement. Current developments in monolithic and hybrid silicon technology, as well as advanced gaseous tracking developments, provide an encouraging road map towards the FCC-ee detector. The current state of the art and potential extensions will be discussed and a generic call for technology which could have a significant impact on the performance of an FCC-ee tracking and vertexing detector is outlined.