Multi-Messenger Constraints on B-L Symmetry Breaking from Colliders to Gravitational Waves

We present a global multi-messenger analysis of B-L gauge symmetry breaking, combining HL-LHC projections, future gravitational wave observatories (LISA, DECIGO, ET), and FCC-hh sensitivities. Our Phase 11.2 global fit achieves 98% reduction in parameter degeneracy (91× → 1.7× at 68% CL), with DECIGO providing 100% coverage of the M_Z'=964 GeV line. Phase 12.0 demonstrates FCC-hh redundancy at 1 TeV but essential role beyond 5 TeV, where it becomes the only viable probe. The high-mass extension (Phase 12.1) shows 40.9-71.3% of parameter space at 5-20 TeV is FCC-hh discoverable (5σ), while HL-LHC and GW constraints vanish. All data and analysis code are publicly available. ## Key Results:1. **98% degeneracy reduction** in B-L parameter space via HL-LHC+GW synergy2. **DECIGO** provides 100% coverage of M_Z'=964 GeV line (LISA/ET blind spots)3. **FCC-hh** redundant at 1 TeV but essential beyond 5 TeV4. **40.9-71.3%** of high-mass parameter space (5-20 TeV) is FCC-hh discoverable5. Complete **open data and code** for reproducibility ## Methods:- Global fit of 3729 parameter points (Phase 11.2)- Hierarchical likelihood combining collider and GW observables- FCC-hh sensitivity projections with conservative systematics- Multi-messenger coverage analysis across 6 future experiments ## Files included:1. Main manuscript (25 pages, PDF)2. Supplementary material (2.1 MB ZIP) with: - Complete analysis code (Python) - All data files (Parquet format) - Figures and tables - Reproducibility scripts ## Citation:Please cite this work using the provided DOI. For questions or data access, contact the author.