Exploring requirements and detector solutions for FCC-ee

Abstract

Circular colliders have the advantage of delivering collisions to multiple interaction points, which allow different detector designs to be studied and optimised—up to four for FCC-ee. On the one hand, the detectors must satisfy the constraints imposed by the invasive interaction region layout. On the other hand, the performance of heavy-flavour tagging, of particle identification, of tracking and particle-flow reconstruction, and of lepton, jet, missing energy and angular resolution, need to match the physics programme and the exquisite statistical precision offered by FCC-ee. During the FCC feasibility study (2021–2025), benchmark physics processes will be used to determine, via appropriate simulations, the requirements on the detector performance or design that must be satisfied to ensure that the systematic uncertainties of the measurements are commensurate with their statistical precision. The usage of the data themselves, in order to reach the challenging goals on the stability and on the alignment of the detector, in particular for the programme at and around the Z peak, will also be studied. In addition, the potential for discovering very weakly coupled new particles, in decays of Z or Higgs bosons, could motivate dedicated detector designs that would increase the efficiency for reconstructing the unusual signatures of such processes. These studies are crucial input to the further optimisation of the two concepts described in the FCC-ee conceptual design report, CLD and IDEA, and to the development of new concepts which might actually prove to be better adapted to the FCC-ee physics programme, or parts thereof.

Dual-Readout Calorimetry for Future Experiments Probing Fundamental Physics

“…Similar sets of requirements, designed specifically for future circular electron-positron colliders, are discussed in Refs. [1,3]. The table links the calorimeter needs to physics goals via technical requirements (TRs).…”

“…states, in particular separation of H → W + W − from H → Z Z when W 's or Z's decay to two jets [4]. At higher energies the separation between the vector boson fusion process Hνν from ZH associated production with Z → νν, which is important in the determination of the Higgs width, also relies on good jet energy resolution [3].…”

The Tracking performance for the IDEA drift chamber

“…The goal is that the reconstruction of the recoil mass is limited by BES rather than by the detector resolution. The very light tracker from IDEA, with a resolution of 0.15% for central, 50 GeV muons, is close to reaching this goal [10]. The (heavier) full silicon tracker of CLD performs a bit worse because the resolution is dominated by multiple scattering in the momentum range of interest.…”

Particle Flow with a Hybrid Segmented Crystal and Fiber Dual-Readout Calorimeter

“…The construction of an electron-positron (e + e − ) Higgs factory, such as the FCC [1], the CEPC [2] or the ILC [3] , is one of the highest priority in the mid-term future of particle accelerators with the objective of accurately measuring the properties of the Higgs boson and hunting for new physics signals. Identification of the key requirements for the detectors that will be recording collisions at such accelerators has started and suggests the need of a high resolution for the measurement of jets to reconstruct events with Z, W or H bosons decaying in their hadronic mode [4,5]. At the same time a detector with high energy resolution for photons enhances the potential of heavy flavor physics studies with low energy photons in their final state [6] and improves the resolution of the 𝑍 → 𝑒𝑒 recoil mass in Higgstrahlung events [7].…”