Baryon Asymmetry as a Boundary Condition: A Sector-Dependent CPT Violation Prediction Testable by BASE-STEP

We introduce a transmission asymmetry parameter δ, defined as half the fractional excess of matter over antimatter at baryogenesis, from which the observed baryon-to-photon ratio η ≈ 6.1 × 10⁻¹⁰ follows by construction: η = 2δ. This parameterization demonstrates that the three Sakharov conditions — baryon number violation, CP violation, and departure from equilibrium — are not independent dynamical requirements but three descriptions of a single observable quantity δ ≠ 0. From δ ≈ 3.05 × 10⁻¹⁰ we derive a prediction for sector-dependent CPT violation: the proton-antiproton magnetic moment comparison should show a fractional asymmetry Δμ/μ ~ δ × O(1), with the O(1) coefficient requiring a nonperturbative QCD calculation deferred to subsequent work. We demonstrate that the null result from ALPHA antihydrogen 1S-2S spectroscopy at 2 × 10⁻¹² precision ALPHA 2018 is quantitatively consistent with this framework: the baryonic CPT-violating signal in the 1S-2S transition is suppressed to approximately 2.4 × 10⁻¹⁹ by the finite nuclear size contribution (~3.9 × 10⁻¹⁰) and the baryonic δ (~3 × 10⁻¹⁰), placing the signal approximately seven orders of magnitude below the ALPHA measurement floor. The framework simultaneously explains the leptonic null result and predicts a baryonic nonzero signal from the same δ. The BASE-STEP experiment at Heinrich Heine University Düsseldorf, targeting proton-antiproton magnetic moment precision of 10⁻¹², provides the definitive test.