Speaker
Description
The precise measurements of the Higgs, W and Z boson properties at the Circular Electron Positron Collider (CEPC) will provide critical tests of the underlying fundamental physics principles of the Standard Model (SM) and are vital in the exploration of new physics beyond the SM (BSM). To distinguish the hadronic decays of W and Z bosons, a 3-4% invariant mass resolution for two-jet systems is required. The particle flow approach, which aims to measure individual particles in a jet using imaging calorimeter system, is a very promising method to achieve the unprecedented jet energy resolution. Therefore, a transverse crystal bar electromagnetic calorimeter (ECAL) is proposed in the 4th conceptual detector. The crystal bar design is expected to provide optimal intrinsic energy resolution and gives three-dimensional shower information for particle flow algorithm (PFA). Besides, the long bar design will dramatically reduce the cost of electronics. The crystal bar ECAL also brings some challenges. The perpendicular arrangement of crystal bars in adjacent layers may cause ambiguity problem for multiple particles. The larger $R_M$ and $X_0/\lambda_I$ for crystal causes more overlap of showers from different particles. Development of a new PFA is needed to solve the above problems.
The key issue of the PFA in ECAL is to associate energy deposits with the correct particles. First, a clustering algorithm is used to gather adjacent hit bars in ECAL. Then, Hough transformation algorithm, track matching algorithm and cone clustering algorithm are applied on the gathered clusters to identify photon showers and energy deposits of charged particles, respectively. Energy splitting algorithm will be activated for the overlap of showers from different particles. In this talk, the updated progress in the new PFA based on the crystal bar ECAL and the preliminary performance will be presented.
