Short-range nuclear effects on axion emissivities by nucleon-nucleon bremsstrahlung

摘要

The rates of axion emission by nucleon-nucleon (NN) bremsstrahlung are reconsidered by taking into account the NN short-range correlations. The analytical formulas for the neutron-neutron, proton-proton and neutron-proton processes with the inclusion of the full momentum dependence of one- and two-pion exchange nuclear potentials, in the non-degenerate limit, are explicitly given. We find that the two-pion exchange (short-range) effects can give a significant contribution to the emission rates, and are temperature dependent. Also, other short-range nuclear effects such as effective nucleon mass, polarization effects and use of correlated wave functions are discussed. The trend of all these nuclear effects is to diminish the corresponding axion emission rates. Furthermore, we estimate that the values of the emission rates calculated with the inclusion of all these effects can differ from the corresponding ones derived with constant nuclear matrix elements by a factor of 24. This leads to an uncertainty factor of 4.9 when extracting bounds of the axion parameters.