  We assess the impact of searches at flavor factories for new neutral
resonances that couple to both photons and gluons. These are well motivated by
"heavy axion" solutions of the strong CP problem and by frameworks addressing
both Dark Matter and the Higgs hierarchy problem. We use LHCb public diphoton
data around the Bs mass to derive the current best limit on these resonances
for masses between 4.9 and 6.3 GeV. We estimate that a future LHCb dedicated
search would test an axion decay constant of O(TeV) for axion masses in the
few-to-tens of GeV, being fully complementary to the low mass ATLAS and CMS
searches. We also derive the impact of BABAR searches based on Upsilon decays
and the future Belle-II reach.
