Prediction of a Narrow Vector State at 3.27 GeV in the Charmonium Spectrum

This is Version 4 (final submission-ready) of the manuscript, all layout defects fixed for single-column preprint format. The PDF contains complete theoretical derivation, systematic uncertainty analysis, and experimental feasibility evaluation for a predicted narrow Jᴾᶜ=1⁻⁻ vector charmonium-like state at 3.27 GeV. Supplementary machine-readable numerical datasets containing all Borel stability curves and mass scan results are attached alongside the manuscript PDF for reproducibility. Core highlights: 1. Standard QCD sum rule framework with OPE up to dimension 6; 2. Full error budget for resonance mass prediction; 3. Clear physical distinction between the predicted e⁺e⁻ initial-state resonance and BESIII’s final-state threshold enhancement; 4. Detailed detection schemes tailored to the BESIII detector and existing data samples. No internal revision logs or appendix materials are included to keep the preprint clean for public archive.