Study of cluster reconstruction and track fitting algorithms for CGEM-IT at BESIII

Considering the effects of aging on the existing Inner Drift Chamber （IDC） of BESIII, a GEM-based inner tracker, the Cylindrical-GEM Inner Tracker （CGEM-IT）, is proposed to be designed and constructed as an upgrade candidate for the IDC. This paper introduces a full simulation package for the CGEM-IT with a simplified digitization model, and describes the development of software for cluster reconstruction and track fitting, using a track fitting algorithm based on the Kalman filter method. Preliminary results for the reconstruction algorithms which are obtained using a Monte Carlo sample of single muon events in the CGEM-IT, show that the CGEM-IT has comparable momentum resolution and transverse vertex resolution to the IDC, and a better z-direction resolution than the IDC.