Spatial parameter from two-pion interferometry

It is proposed that the average radius of the source obtained from two-pion interferometry analyses is a suitable quantity to describe the spatial size of the source by comparing the correlation functions from different source density distributions directly. When comparing the source spatial parameters from different correlation functions, the average radius of the source is a superior standard parameter to the root-mean-square radius suggested by Bartke and Kowalski, and is superior to the factor suggested by Goldhaber et al. A systematic study of the results from different heavy ion experiments demonstrates that a more reasonable result can be obtained by utilizing the average radius as a standard for comparison