Muon Collider

Muon Collider
Name	Muon Collider
Type	Particle collider
Location	Proposed international sites
Status	Research and development
Participants	Fermilab, CERN, SLAC, INFN, KEK, JINR, DESY, IHEP, BNL, PSI

Muon Collider

A Muon Collider is a proposed high-energy particle collider concept that would accelerate and collide beams of muons to study electroweak interaction, search for Higgs boson properties, probe Beyond Standard Model physics, and investigate Quantum Chromodynamics. Advocates include researchers from Fermilab, CERN, SLAC National Accelerator Laboratory, Brookhaven National Laboratory, and national laboratories such as DESY and KEK. The project intersects with programs at facilities like the Large Hadron Collider, the International Linear Collider, and the Future Circular Collider, and involves collaborations with universities and institutes including MIT, Stanford University, University of California, Berkeley, Oxford University, University of Tokyo, and INFN.

Introduction

The concept originated from proposals in the 1960s and was developed through studies at Brookhaven National Laboratory and Fermilab in the 1990s and 2000s, with renewed attention after discoveries at the Large Hadron Collider and precision goals set by Particle Data Group analyses. A Muon Collider aims to combine high center-of-mass energy ambitions of projects like the Future Circular Collider with the compact footprint sought by proposals such as the Compact Linear Collider. Key institutions involved include CERN Accelerator School, US Particle Accelerator School, Argonne National Laboratory, Paul Scherrer Institute, and Lawrence Berkeley National Laboratory.

Physics Motivation and Advantages

Muon collisions provide direct access to Higgs boson s-channel production, enabling precision measurements of couplings and searches for rare decays emphasized by communities represented at the European Organization for Nuclear Research workshops and reports from the Particle Physics Project Prioritization Panel and the High Energy Physics Advisory Panel. Compared with proton colliders like the Large Hadron Collider, muon collisions offer cleaner initial states similar to proposals such as the International Linear Collider, enhancing sensitivity to phenomena predicted by Supersymmetry models, Composite Higgs scenarios, and signatures from Dark Matter portals explored by collaborations at SLAC and CERN. A Muon Collider can reach multi-TeV center-of-mass energies with smaller synchrotron radiation losses than electron machines discussed in LEP and CEPC histories, enabling comparisons with results from ATLAS and CMS detectors.

Accelerator and Collider Design

Design work builds on technologies developed at Fermilab Accelerator Division, CERN Accelerator Complex, and projects such as NuMI and Project X. Core elements include high-power proton drivers akin to those at Spallation Neutron Source and J-PARC, target stations similar to ISIS Neutron and Muon Source and Mercury Target designs, and capture systems using high-field solenoids developed by collaborations with Princeton Plasma Physics Laboratory and Jefferson Lab. Collider rings draw on lattice concepts from SPS (accelerator), RHIC, and novel designs from Paul Scherrer Institute studies, while RF systems and superconducting magnet technology parallel developments at ITER and CERN Magnet Lab.

Beam Production, Cooling, and Injection

Muon production follows schemes studied at MICE and MERIT experiments: a high-intensity proton beam strikes a heavy-metal target producing pions that decay to muons, with capture and phase rotation stages tested in prototypes at ISIS and CERN. Critical is six-dimensional ionization cooling demonstrated by the MICE Collaboration and proposed cooling channels using high-gradient RF cavities and strong solenoids developed by teams at Oak Ridge National Laboratory, DESY, INFN-LASA, and KEK. Injection strategies leverage timing and transfer techniques from PSR and Booster systems at Fermilab and Brookhaven, with stochastic and deterministic manipulations informed by expertise at Los Alamos National Laboratory.

Detector Challenges and Experimental Program

Detectors must operate in intense backgrounds from muon decays; designs adapt solutions from CMS, ATLAS, LHCb, and proposed detectors for the ILC and FCC-ee. Fast timing layers, radiation-hard sensors pioneered at CERN-RD50 and technologies from SLAC and LBL are essential. Physics programs target precision Higgs width and coupling measurements relevant to analyses by the Particle Physics Community Planning Process and searches for new resonances predicted by Grand Unified Theory-inspired models and Z' boson scenarios studied at Tevatron and LEP. Detector R&D leverages pixel and calorimeter innovations from ALICE, Belle II, and DUNE collaborations.

Technical Challenges and R&D

Major challenges include rapid muon beam cooling within the muon lifetime, high-power target survivability studied in the MERIT experiment, and mitigation of machine-induced backgrounds informed by simulations used by GEANT4 and FLUKA communities. Superconducting magnet development must meet demanding fields similar to those pursued for High-Luminosity LHC and FCC-hh magnets, with materials science input from CERN, Oxford Materials Science, and Tokyo University groups. Accelerator systems require high-gradient RF cavities that operate in magnetic fields, an area of concurrent research at SLAC and Cornell University.

Global Projects and Timeline

International coordination is guided by panels such as the European Strategy for Particle Physics and the US Particle Physics Project Prioritization Panel, with contributions anticipated from Fermilab, CERN, KEK, JINR, and national agencies including DOE, CNRS, INFN, RIKEN, and MEXT. Conceptual design reports and feasibility studies are ongoing, with staged timelines discussed in workshops at Snowmass (scientific program), IPAC, and meetings convened by IHEP (China). Realistic projections place an initial demonstration facility and technology testbed in the 2020s–2030s, with a possible multi-TeV collider construction in the 2040s contingent on R&D outcomes and global prioritization articulated by the International Committee for Future Accelerators and national funding agencies.

Category:Particle accelerators