Axions beyond gen 2

Abstract

The QCD (Quantum ChromoDynamics) axion emerged as one of the best-motivated dark matter candidates. In 2018, the Axion Dark Matter eXperiment (ADMX), one of the U.S. Department of Energy's Gen 2flagship dark-matter projects, demonstrated first sensitivity to the highly plausible DFSZdark matter axion couplings over a small frequency range. We anticipate this development marks the first step in constructing yet more powerful experiments that can explore large swaths of the axion parameter space at high sensitivity and result in a discovery. But, realizing this requires advances in both our understanding of the theory and experiment design. Between 25 January and 27 January 2021, the Axions Beyond Gen 2 Workshopwas held, where selected members of the community discussed our broad understanding of the QCD axion and charted a course for future experiments having sensitivity and mass reach well beyond the current Gen 2experiments. These proceedings are summaries of the topics presented and discussed. © 2023 The Author(s).