The 17 MeV Anomaly and SGCU Geometric Structure: Surface Mode or Independent Particle — A Rigorous Derivation

The 17 MeV anomaly (X17 particle) observed by the ATOMKI experiment has sparked extensive theoretical speculation. This paper, within the SGCU (Cosmic Topology) framework, provides two possible geometric interpretations of the 17 MeV anomaly from first principles: (1) 17 MeV is a surface-localized mode of the SGCU-predicted 47 MeV resonance, with mass mₒₔₑ₅₀₂₄ m_ / 8 16. 6 MeV; (2) 17 MeV is the ground-state scalar resonance of an N=2 soliton, rendered metastable by nuclear medium effects. We rigorously derive the mass formulas, quantum numbers, coupling strengths, and decay characteristics for both possibilities, and present a decisive experimental test to distinguish them. The core prediction is: if the 17 MeV anomaly is a surface mode, then a bulk-mode resonance peak must exist at 47 MeV; if it is an independent particle, no such peak is required. This decisive test can be performed with existing data from Belle II and BESIII. This revised version includes a first-principles derivation of the surface-mode mass factor 1/8, a nuclear-medium stabilization mechanism for the N=2 soliton lifetime, an angular-distribution-asymmetry-based experimental search strategy, strategies for addressing the collinear limit at high-energy colliders, and an SGCU–standard field theory glossary.