Concerning tests of time reversal invariance via the polarization‐analyzing power equality

It is shown that one of the more recent tests of time reversal invariance via measurements of the polarization and the analyzing power in p+13C elastic scattering, does not, in fact, provide a significant test of time reversal invariance. This follows from the fact that the polarization‐analyzing power equality depends on the equality of the two possible spin‐flip probabilities. A possible non‐zero difference between the spin‐flip probabilities was beyond the precision of the experiment simply because the individual spin‐flip probabilities are so small. It is immediately clear that tests of time reversal invariance should be made through measurements of the polarization and analyzing power in a reaction (and its inverse) where the spin‐flip probability is expected or known to be large.It is shown that one of the more recent tests of time reversal invariance via measurements of the polarization and the analyzing power in p+13C elastic scattering, does not, in fact, provide a significant test of time reversal invariance. This follows from the fact that the polarization‐analyzing power equality depends on the equality of the two possible spin‐flip probabilities. A possible non‐zero difference between the spin‐flip probabilities was beyond the precision of the experiment simply because the individual spin‐flip probabilities are so small. It is immediately clear that tests of time reversal invariance should be made through measurements of the polarization and analyzing power in a reaction (and its inverse) where the spin‐flip probability is expected or known to be large.