Magnetic Characterization of Target Plates for an Experiment to search for Z' Boson Axial Vector Couplings to the Neutron

We plan to conduct a slow neutron spin rotation experiment to search for possible weakly-coupled $Z'$ bosons to the neutron via an interaction of the form $V_{5}=\frac{g^{2}_{A}}{4\pi m}\frac{e^{-m_{0}r}}{r}(\frac{1}{r}+\frac{1}{\lambda_{c}})\vec\sigma\cdot(\vec v\times\hat r)$. A previous experiment [1] reported $\phi < 4*10^{-6}$ $rad/m$ for the neutron spin rotation angle accumulated by polarized neutrons passing very close to a set of $1/2$ m copper plates [2], and we anticipate magnetic impurities may be our dominant source of systematic error. We discuss a B-field mapping apparatus our group has constructed consisting of a QuSpin Zero-Field Magnetometer and Parker motors to search for magnetic impurities embedded in the target plates. The data analysis must see fields near the limit of the probe noise ($\sim$pT) in the presence of slowly-varying background magnetic fields ($\sim$nT). We discuss our results for maps of glass, copper, and tungsten plates from implementing ABBA data measurement patterns [3] and low-degree polynomial drift subtraction of time-dependent effects. \\\\{[1]} C. Haddock et al., Phys. Lett. B 783 (2018)\\{[2]} C. Haddock et al., Nucl. Inst. Meth. A 885 (2018)\\{[3]} H.E. Swanson and S. Schlamminger, Meas. Sci. Technol. 21 , 115104 (2010)