$\Xi_{cc}(3621)$ Axial Partner: A QCD Sum Rule Analysis

This is the final single-column revtex4-2 preprint of the QCD sum rule study for the $J^P=1^+$ axial partner of the ground-state $\Xi_{cc}(3621)$ doubly charmed baryon. All LaTeX code is fully debugged for pdflatex compilation without table or macro errors. Main research highlights: 1. Dedicated diquark interpolating current constructed for the $\Xi_{cc}^*$ $1^+$ state, with OPE expanded up to dimension 8 using modern PDG2025 vacuum condensates; 2. Quantitative mass prediction $3.75\pm0.08\ \text{GeV}$ and natural strong decay width $12$–$18\ \text{MeV}$; 3. Systematic comparison among three theoretical pictures: conventional constituent baryon, $\Xi_{cc}\pi$ molecular state, and compact diquark excited baryon; 4. Clear experimental discrimination strategies designed for LHCb Run 4 high-luminosity data. Supplementary machine-readable data including full Borel stability scan curves and OPE Wilson coefficient tables are uploaded together with the manuscript PDF for full numerical reproducibility. No internal revision logs or draft attachments are included to keep the archive clean.