Two-dimensional simulations of beam energy calibration using Compton scattering method

Abstract

The Circular Electron-Positron Collider (CEPC) performs precision measurements of Higgs boson properties, which require MeV-level precision in beam energy calibration. In the W/Z factory mode, the requirements for beam energy calibration are an order of magnitude higher than those in the Higgs operation. To address this need, we utilize a beam energy calibration scenario based on inverse Compton scattering, using a laser beam heading on the electron bunch and a bending dipole. Our Monte-Carlo simulations demonstrate that the beam energy can be calibrated to a precision of about 1 MeV, using the position distribution of scattered photons and scattered electrons. Additionally, the systematic deviations caused by the magnetic field and the synchrotron radiation are analyzed. The error of the method of measuring the scattering position by measuring the scattering angle is divided into two parts, which are 9.75 and 5.76 MeV, respectively. The estimated systematic deviation of the calibration energy caused by the electron beam emittance angle is approximately 3.4 keV.