The ILC Vertex Detector requirements

Abstract

After few decades of R&D, the International Linear Collider (ILC) project has reached a level of maturity proving the feasibility of the machine and of the detectors. The ILC physics goals cover a very wide and ambitious program including top-quark quark physics, electroweak precision measurements, direct and indirect searches beyond the Standard Model (BSM) like SUSY, dark matter manifestations, exotic particles and phenomena, etc., and an extensive Higgs physics program covering mass, couplings to fermions and bosons, quantum numbers and total width measurements. These measurements are expected to reach an unprecedented level of precision, which will allow probing physics BSM, since typical deviations from the Standard Model are expected to be within the ILC sensitivity. To accomplish the ambitious physics program of the ILC, the vertex detector will be essential for providing the necessary physics performances in terms of flavour tagging, displaced vertex charge determination and low momentum tracking capabilities. Taking advantage of the much less demanding running conditions at the ILC than at hadron colliders like LHC, the vertex detector is expected to reach particularly high performances as far as spatial resolution and material budget are concerned (typical impact parameter resolution of the order of 5 microns and material budget in the order of 0.15-0.2 % of radiation length per layer). In addition, the particular time structure of the beams has major consequences on the specifications of the detectors and their read-out architecture. Finally, the beam related background of the ILC, which translates into a high rate of low momentum-$e^{-}e^{+}$ pairs hitting the vertex detector, drives the expected occupancy (and the related necessary read-out speed) as well as the radiation load. This article focuses on the vertex detector requirements driven from the stringent physics and experimental constraints of the ILC. Wherever different, the aspects to each detector concepts (SiD and ILD) are discussed.