The Level 1 / Level 2 Boundary — From Observed Structure to Unobserved Particles: The integers tell you WHAT. The universe tells you HOW MUCH.

The Level 1 / Level 2 Boundary — From Observed Structure to Unobserved Particles: The integers tell you WHAT. The universe tells you HOW MUCH. This paper is part of the HOWL research archive—a collection of physics papers exploring integer fraction derivations across multiple domains using exact arithmetic and automated comparison. Abstract Every HOWL paper from PHYS-7 through PHYS-20 classifies its results as Level 1 (determined by the mathematical framework) or Level 2 (supplied by the universe through measurement). These classifications are scattered across individual appendices. This paper assembles them into a unified boundary map, states the principle explicitly, and documents its extension to an unobserved particle for the first time. The Cabibbo Doublet (3,2,1/6) is the first entity in the series where Level 1 arithmetic — exact Fraction computation on gauge group integers — identifies WHAT should exist before Level 2 measurement has confirmed WHETHER it exists. The representation, beta contributions, gap ratio, asymmetry mechanism, and scaling laws are all Level 1. The mass, mixing angles, CP phases, and the very existence of the particle are all Level 2. This extension from confirmed structure to unconfirmed identification is the same pattern that operated for every particle discovered since 1974: Level 1 mathematics identified the charm quark (GIM, 1970), the W and Z bosons (SU(2)×U(1), 1967), and the Higgs boson (symmetry breaking, 1964) before Level 2 experiments found them. The Cabibbo Doublet is at the same stage. Whether it follows the same path is for the universe to say. Falsification Criteria All papers in this archive are subject to falsification through direct comparison to published experimental measurements. Each derived value is tested against independent data with explicit PASS/FAIL criteria. Any derived value that fails its comparison is documented and published alongside the successes. Research Context This archive documents an ongoing research program in integer fraction physics. The methodology is: derive values from gauge group integers using exact fraction arithmetic, compare to published measurements, and document all results including failures. The archive spans multiple physics domains connected through the soliton boundary framework described in the constituent papers. Package Contents manuscript.md: The complete derivation and supporting analysis. README.md: Navigation, dependencies, and citation (Registry: HOWL-PHYS-21-2026). Dependencies: HOWL-PHYS-1-2026, HOWL-PHYS-10-2026, HOWL-PHYS-11-2026, HOWL-PHYS-12-2026, HOWL-PHYS-13-2026, HOWL-PHYS-14-2026, HOWL-PHYS-15-2026, HOWL-PHYS-17-2026, HOWL-PHYS-18-2026, HOWL-PHYS-19-2026, HOWL-PHYS-2-2026, HOWL-PHYS-20-2026, HOWL-PHYS-6-2026, HOWL-PHYS-7-2026, HOWL-PHYS-8-2026, HOWL-PHYS-9-2026 Motto: Derive. Compare. Publish.Status: Complete