Measurement of two particle resolution in silicon drift detectors

A study resolving two hits in a 45/spl times/45 mm rectangular n-type Silicon Drift Detector is presented as a function of drift field using a pulsed Nd:Yag laser. The data are analyzed under the assumption of the general form of a Gaussian distribution in two variables (including correlations). The two hit resolving power degrades with drift distance. As the two electron clouds approach each other their correlation coefficients are shown to increase and be anti-correlated. Arguments for optimal two hit resolution versus drift field are presented. A simple method to determine whether electron cloud distributions arise from multiple overlapping hits or single hits is demonstrated. Practical implications for analyzing data from high occupancy experiments such as STAR at the RHIC collider are discussed.