= Analogue beta-decay branching estimate
{title2=$B_X=(\tau_P/\tau_R)(f_X/f_R)(S_X/S_R)$}
Compare an unknown allowed branch of parent $P$ with a reference allowed decay of mean lifetime $\tau_R$ and unit branching fraction. Its <branching fraction> is the parent mean lifetime $\tau_P$ times the inferred partial rate. The phase-space ratio $f_X/f_R$ and the total vector-plus-axial strengths $S_X/S_R$ enter separately. Approximating both strengths by their <Fermi transition> contributions and both phase-space integrals by $Q^5$ gives a useful scale, but does not establish a unique branch fraction if the axial strengths are unknown.
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