= Solution
The baryon excess requires a mechanism that produces different net <baryon numbers> from an initially symmetric ensemble. In the usual local, CPT-invariant framework, the <Sakharov conditions> are baryon-number violation, C and <CP violation>, and departure from <thermal equilibrium>. Baryon conservation would preserve zero net <baryon number>; exact conjugation symmetries equate the conjugate production processes; equilibrium inverse reactions and <detailed balance> erase a would-be asymmetry. These necessary conditions do not determine its magnitude.<Violation of CP invariance, C asymmetry, and baryon asymmetry of the universe by Andrei Sakharov>[1967 original statement of the conditions]{ref}
For example, let equal numbers of a heavy particle $X$ and its <antiparticle> decay into channels $i$ with <baryon numbers> $B_i$. Their mean net yield per pair is
$$
\epsilon_{\rm pair}=\sum_i B_i\left[\operatorname{Br}(X\to i)-\operatorname{Br}(\bar X\to\bar i)\right].
$$
It can be nonzero even though CPT requires equal total widths: the <branching fractions> differ among channels carrying different <baryon numbers>. A nonzero decay-rate asymmetry requires interference with both a CP-odd <weak phase> and an <absorptive phase>. If the expansion rate overtakes the inverse-reaction rate, decays can occur out of equilibrium; later baryon-violating washout must then be weak enough for the asymmetry to survive.
In electroweak <baryogenesis>, CP-asymmetric transport near a first-order phase-transition boundary can bias baryon-violating <sphaleron> transitions. <CP violation> alone is insufficient: the transition and washout dynamics also matter. In <leptogenesis>, out-of-equilibrium decays of heavy <Majorana neutrinos> can generate <lepton> asymmetry, part of which <sphalerons> convert into baryon asymmetry while conserving $B-L$. The CKM phase demonstrates <CP violation> in the <Standard Model> but does not by itself supply a successful cosmological mechanism. \b[The key quantity is a surviving net charge yield, not merely the existence of a CP-violating reaction.]
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