Quark mass uncertainties revive KSVZ axion dark matter

Understand

The Kaplan-Manohar ambiguity in light quark masses allows for a larger uncertainty in the ratio of up to down quark masses than naive estimates from the chiral Lagrangian would indicate.

• We show that it allows for a relaxation of experimental bounds on the QCD axion, specifically KSVZ axions in the $2-3 \mu$eV mass range composing 100% of the galactic dark matter halo can evade the experimental limits placed by the ADMX collaboration.