Study of the Beamstrahlung Effects at the CEPC

Abstract: The discovery of a 125 GeV Higgs boson at the LHC marked a breakthrough in particle physics. The relative lightness of the new particle inspires the consideration of a high luminosity Circular Electron Positron Collider (CEPC) as a Higgs Factory to study the Higgs boson in a clean environment. At the CEPC, the beamstrahlung might represent one of the most important sources of beam-induced backgrounds that will impact the detector. It will introduce additional backgrounds to the CEPC detector through the subsequent electron-positron pair production and the hadronic process. Therefore its impacts should be carefully evaluated. In this paper, the beamstrahlung-induced backgrounds are first estimated with analytical methods and are further evaluated in detail with Monte Carlo simulation. The detector occupancy due to the beamstrahlung at the location where the first vertex detector layer may be placed is found to be well below 0.5%. Radiation levels characterised as non-ionising energy loss (NIEL) and total ionising dose (TID) are estimated to be ~ $10^{11} 1 $ MeV $ n_{eq}/cm^2/$yr and ~ 300 kRad/yr, respectively.