The CP Asymmetry Required Per Decay, From Weak to Strong Washout

How large must the matter-antimatter preference in a single particle decay be, to account for the observed baryon asymmetry? This paper tabulates the answer across the full range of washout efficiencies, for direct baryon production and for leptogenesis with its sphaleron conversion factor. At efficiency kappa = 0.1 the required CP asymmetry is 9.28e-08 for direct production and 2.62e-07 for leptogenesis; at kappa = 0.5 the direct requirement falls to 1.86e-08; in strong washout, kappa = 0.001, the requirements rise to 9.28e-06 and 2.62e-05 respectively. The leptogenesis column is uniformly a factor of about 2.8 above the direct column, the price of the 28/79 conversion. These numbers set the target that any model's loop-level CP calculation must hit, and they show why strong washout demands either resonant enhancement or a different mechanism. Computed from stated assumptions, not measured.