Constraints on axions from SN 1987A

We argue that the detection of neutrinos from SN 1987A implies that axion emission from the collapsing star must not have been significant. The best axion supernova limits come from nucleon bremsstrahlung processes which involve axion-quark couplings rather than the electron or photon couplings used in obtaining axion limits from red giants. The axion-quark couplings are less sensitive to specific axion model parameters and therefore are capable of yielding a model independent lower bound on fa. Quantitatively this yields an axion coupling limit of fa > or approx. 8x1011 GeV (or equivalently ma < or approx. 9x105 eV). This approaches the upper bound on fa < or approx. 4x1012 GeV from cosmological density arguments. While the bounds do not exclude the axion, if the axion exists, it must dominate the cosmological mass density. This same argument can also be applied to analogous couplings for any particle with m > or approx. 50 MeV. (orig.)