Axion-Like Particle Conversion in Cluster Magnetic Fields: Probabilities Against the CAST Bound and the Bounce Scale

For a massless particle at a coupling of 10^-12 per GeV the single-domain probability is 2.33e-04; at 10^-11 per GeV it rises to 2.33e-02, scaling as the square of the coupling, and at 10^-13 per GeV it falls to 2.33e-06. A mass of 10^-9 eV at the middle coupling suppresses the probability to 1.53e-15, because the oscillation phase across the domain becomes large and the sine factor averages down. The field used corresponds to 1.95e-08 eV^2 and the domain to 1.56e+27 inverse eV. None of these numbers samples the bound density of 9.72e+54 g per cubic centimetre; cluster plasma is a present-day, low-density environment. This study is computed from stated assumptions and published comparison values; it is not a measurement.