Progress Towards an Order of Magnitude Improved ACME II Measurement of the Electron Electric Dipole Moment

The search for the electron electric dipole moment (eEDM) is a powerful probe of physics beyond the Standard Model. In 2014, the first generation of the ACME experiment set the most stringent upper limit on the eEDM of $|d_e|<0.9\times10^{-28}$ e$\cdot$cm by measuring spin precession in a beam of thorium monoxide (Science \textbf{343} (2014), 269). Since then, we have implemented improvements in signal, such as STIRAP preparation of the experimental measurement $^3\Delta_1$ state, optimized apparatus geometry, and enhanced detection efficiency, which have increased our statistical sensitivity by an order of magnitude (Phys. Rev. A \textbf{93} (2016), 052110). We describe recent progress in the ACME II measurement, including a discussion of data analysis and modeling and suppression of systematic errors.