Progress toward an ultracold trap of SrOH molecules to probe fundamental constant variations and the electron electric dipole moment*

We present experimental progress towards laser slowing and trapping of SrOH molecules. The long coherence times possible in a trapped, ultracold sample will enable two complementary searches for beyond-the-Standard-Model physics. First, because vibrational and rotational energies of molecules generically depend on the proton-to-electron mass ratio, μ, certain dark matter models that induce oscillations in μ can be probed via precision spectroscopy of rovibrational transitions. A low-lying accidental near-degeneracy between stretching and bending vibrational states in SrOH can be probed with experimentally convenient microwave transitions. Second, the nearly-degenerate opposite-parity states of the bending vibrational mode provide access to the moderate effective electric field of 2 GV/cm at small externally applied fields, and also serve as co-magnetometer states. Combined with the long coherence times and large numbers possible in a trap of ultracold SrOH molecules, we anticipate competitive sensitivity to the electron electric dipole moment. We describe recent developments of the experimental apparatus, including a new cryogenic buffer gas beam source, the full laser slowing and cooling system comprised of 10 sum-frequency-generated lasers, and work toward 2D transverse cooling for increased loading efficiency into a magneto-optical trap.