Cherenkov Light Identification to Improve Axion Searches on the Coherent CAPTAIN-Mills Experiment*

The CCM experiment is a 10 ton liquid argon scintillation detector located at Los Alamos National Lab. The detector is located 23m downstream from the Lujan Facility’s stopped pion source which will receive 2.25 x 10²² POT in the ongoing 3 year run cycle. Instrumented with 200 8-inch PMTs and 40 optically isolated 1-inch veto PMTs, CCM can resolve signals across a wide energy spectrum. CCM has sensitivity to nuclear recoil events around 10s of keV to electromagnetic signals in the 100s of MeV region. While the engineering run in 2019 set world leading limits on leptophobic dark matter searches using scintillation light, upcoming analyses are incorporating Cherenkov ring reconstruction to reduce sources of backgrounds in axion searches. Using data from the upcoming run cycle and Cherenkov light identification, CCM has sensitivity to probe the cosmological triangle region as well as QCD axion bands.