Wuzheng Meng <meng@bnl.gov> made 2D calculations of STAR magnetic field for 4 different sets of extra magnetic material on back of West Pole Tip (dZ = 0, 5, 10 and 15 cm).
These plots are difference between Wuzheng's calcaulation and STAR measured magnetic field.

Below the plots for Br and Bz (left and right colomns) for dZ = 0 (the first row), and difference for Br and Bz between histograms dZ != 0 and dZ == 0 are presented.