In situ detector calibration at CLIC

The Compact LInear Collider (CLIC) is proposed to run according to a staging scenario with centre-of-mass energies increasing from √s = 380 GeV to 3 TeV. Achieving good physics performance requires accurate alignment and calibration of the detector as well as regular monitoring of the alignment and calibration parameters. During physics runs this is achieved using particles from ee, eγ and γ γ interactions. Standard Model cross sections depend on the centre-of-mass energy. As a result, processes relevant for calibration are different at the different energies. This note discusses the main detector calibration topics at two different centre-of-mass energies of CLIC, √s = 380-350 GeV and 1.5 TeV. It estimates the total and differential muon rates available for the detector alignment as well as the performance reachable for the momentum scale and total energy scale calibration. For the first stage of CLIC, special calibration runs at √s = 91.2 GeV are also considered. After the first year of running the high muon rate allows an accurate alignment and a regular control of the alignment parameters. Z → μ μ and KS → π + π events allow a good control of the momentum resolution and an accurate determination of the global and differential momentum scale. At √s = 91.2 GeV the di-muon event sample provides a direct measurement of the momentum resolution and an accurate determination of the momentum scale. The di-jet event sample allows for a direct measurement of the di-jet energy resolution and a good determination of the di-jet energy scale. It allows also for the measurement of the flavour tagging efficiency. At the lowest centre-of-mass energy a measurement of the top mass will be done measuring the top production cross section in the energy range √s = 340 GeV to 350 GeV. This note presents also the method to measure the absolute centre-of-mass energy and the accuracy reachable for the top threshold scan.