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μLHC – Antimuon-Proton Collider Conceptual Design (HL-LHC Based)
A June 2026 arXiv preprint presents a conceptual design for a μLHC — an antimuon-proton collider achieving 5.3 TeV center-of-mass energy by combining HL-LHC proton ring infrastructure with J-PARC ultra-cold muon beam technology. The design reportedly surpasses both EIC and LHeC in energy reach while reusing existing CERN infrastructure. The concept is at an early design stage with no formal funding commitment.
Importance: 52%Confidence: 70%Mentions: 1Updated: June 16, 2026
## μLHC – Antimuon-Proton Collider Conceptual Design
### Overview
A conceptual design study for an antimuon-proton collider (μLHC) leveraging the High-Luminosity LHC (HL-LHC) infrastructure has been presented in arXiv:2506.15445 (updated June 2026). The design reportedly could achieve a 5.3 TeV center-of-mass energy, significantly surpassing existing and planned lepton-proton colliders.
### Key Technical Parameters
According to arXiv:2506.15445v2 (June 2026):
- **Center-of-mass energy**: 5.3 TeV — described as "significantly surpassing" both the Electron-Ion Collider (EIC) and the Large Hadron-electron Collider (LHeC) (arXiv:2506.15445, June 2026)
- **Technology basis**: Leverages the μTRISTAN concept, which is based on established J-PARC ultra-cold μ⁺ beam technology (arXiv:2506.15445, June 2026)
- **Booster ring options**: Two options explored — a μTRISTAN-based system and a repurposed LHeC Energy Recovery Linac (ERL)-based system (arXiv:2506.15445, June 2026)
- **Luminosity**: Predicted to exceed 10³³ cm⁻²s⁻¹ (arXiv:2506.15445, June 2026)
- **Infrastructure**: Designed to use the existing HL-LHC proton ring, reducing new construction requirements
### Scientific Significance
- A muon-proton collider at 5.3 TeV would open a new window on quark-gluon structure, electroweak physics, and potential beyond-Standard-Model phenomena
- The use of antimuons (μ⁺) rather than electrons reduces synchrotron radiation losses, enabling higher energy in a compact ring
- The J-PARC ultra-cold muon beam technology is described as "established," suggesting the key enabling technology exists (arXiv:2506.15445, June 2026)
### Strategic & Policy Implications
- **For CERN governance**: The proposal represents a potential future use case for HL-LHC infrastructure post-Run 4/5, relevant to long-term CERN program planning
- **For Japan (J-PARC)**: Positions J-PARC muon beam technology as a critical enabler for next-generation collider physics, strengthening Japan's role in global HEP infrastructure
- **For funding agencies**: A design leveraging existing HL-LHC infrastructure may offer a cost-competitive path to TeV-scale lepton-proton physics relative to greenfield collider proposals
### Status
Conceptual design phase; no formal approval or funding commitment reported as of June 2026.