Analysis of the APEX Experiment Data

The A Prime Experiment (APEX) at Jefferson Lab took data for the search for the dark matter force mediator, A', in the mass range 160-230 MeV decaying to electron-positron pairs with statistics corresponding to the signal sensitivity on the level of coupling constant 10$^{\mathrm{-9}}$. We will present the results on the magnetic optics for accurate reconstruction of the particle momenta for the APEX configuration of the High Resolution Spectrometers (HRS) with a septum magnet. Preliminary results show that angular reconstruction could be accomplished with a precision of 0.5 msr or better.