Development Of A CMOS Pixel Based Inner Tracker For The BES-? Experiment At BEPC-?

The thesis addresses the upcoming particle physics programme foreseen at the Beijing Electron Positron Collider II(BEPCII),for which the Beijing Electron Spectrometer III(BESIII)is being upgraded.The work presented focused on the upgrade of the central tracker of the experiment by exploring the possibilities offered by a new approach using CMOS Pixel Sensors(CPS)instead of the present gas drift chamber.The MDC inner chamber of BES? suffers from ageing effects which lead to performance degrading in terms of detection efficiency,momentum resolu-tion and spatial resolution.From the analysis in 2013,the efficiency of the MDC inner cell could be around 70%and its spatial resolution degraded from?120 ?mto?300 ?min the worst case.This ageing effect would prevent BES-III from collecting the foreseen data sample and decrease the precision of the measurements.The collaboration decided therefore to upgrade the original in-ner chamber with a newly designed one or with a tracker using more advanced technology.The project of a Silicon Pixel Tracker(SPT)was proposed in this perspective.Two issues in SPT development have been studied:a low material budget of a long ladder and the detecting geometry optimization.CPS prototypes using large pixel pitches and an improved rolling-shutter readout architecture have been tested and studied to validate the sensor performance of a spatial resolu-tion?10 ?m,an integration time?20.8 ?s and a power consumption around 80mW/cm2,As for tracker optimization,a general method and the related software based on tracking algorithms,numerical geometry scans and Geant4 Monte-Carlo simulations,have been developed and applied for BES? SPT.The total number(3)of ladders and the tracker layout with a uniform spacing have been determined for the optimal momentum measurement for a sensor spatial resolution?10 pmand for a ladder material budget?0.36%X0.To achieve a higher tracking efficiency,a double-sided ladder may be considered to replace the innermost one-sided one with acceptable tracking performance degradation for low momentum trajectories.