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| MuLan collaboration | |
|---|---|
| Name | MuLan collaboration |
| Field | Particle physics |
| Founded | 1999 |
| Locations | Paul Scherrer Institute, Fermi National Accelerator Laboratory, Brookhaven National Laboratory |
| Notable members | Tim Gorringe, David W. Hertzog, Kevin J. Lynch, D. Pocanic, A. Pineda |
| Instruments | muon (elementary particle), muon lifetime experiment, electrostatic kicker |
MuLan collaboration The MuLan collaboration was an international experimental team that measured the positive muon lifetime to high precision, providing a determination of the Fermi coupling constant G_F and testing aspects of the Standard Model. Comprised of researchers from national laboratories and universities, the collaboration combined expertise in accelerator physics, detector technology, and precision timing to perform lifetime and decay asymmetry studies using pulsed muon beams. Its work intersected with precision efforts at facilities such as Paul Scherrer Institute, Fermi National Accelerator Laboratory, and TRIUMF and influenced subsequent measurements in weak interaction physics.
The collaboration formed in the late 1990s, drawing scientists from institutions including University of Washington, University of Illinois at Urbana–Champaign, Yale University, Boston University, Indiana University, University of British Columbia, Simon Fraser University, University of Chicago, University of Wisconsin–Madison, University of Virginia, Northwestern University, Rutgers University, University of Kentucky, University of Manitoba, University of Kentucky (duplicate institutions were avoided in planning), and national laboratories such as Fermi National Accelerator Laboratory and Brookhaven National Laboratory. Early conceptual work referenced prior muon studies at CERN, TRIUMF, and experiments by groups connected to Paul Scherrer Institute and Los Alamos National Laboratory. Funding and oversight interacted with agencies including National Science Foundation (United States), Department of Energy (United States), and Canadian research councils. The team organized workshops and steering meetings at facilities like Fermilab and university hosts, aligning with contemporaneous precision programs such as the Muon g−2 experiment.
Primary goals included a sub-part-per-million measurement of the positive muon lifetime τ_μ and extraction of the Fermi coupling constant G_F with minimized systematic uncertainties. The methodology built on pulsed-beam techniques used in past experiments at TRIUMF and Paul Scherrer Institute, employing an electrostatic kicker to create time-structured muon bunches and reduce background from overlapping events. Data acquisition relied on fast waveform digitizers similar to technology developed for the MuCap experiment and timing calibration methods influenced by systems at Fermilab and Brookhaven National Laboratory. Systematic control incorporated targets drawn from materials studies at Argonne National Laboratory and spin-rotation mitigation strategies paralleling those used in TWIST (experiment) and PIENU experiment.
The detector array combined segmented plastic scintillator arrays, photomultiplier tubes of types used at SLAC National Accelerator Laboratory, and high-speed digitizers developed in collaboration with electronics groups at Brookhaven National Laboratory and Fermilab. A symmetric, near-4π geometry reduced acceptance biases analogous to designs used by SNO (Sudbury Neutrino Observatory) and Super-Kamiokande, while muon beamline components were adapted from M20 beamline practices at TRIUMF and beamline optics expertise at Paul Scherrer Institute. Magnetic field control and muon spin manipulation referenced techniques from Muon g−2 experiment and MEG experiment; cryogenics and target handling invoked infrastructure common to ISIS Neutron and Muon Source and facilities at Los Alamos National Laboratory.
The collaboration published a suite of papers reporting a precision measurement of the positive muon lifetime and derived values of G_F, comparing results to theoretical calculations by groups associated with Stefan Weinberg, Fee J. Marciano, and radiative correction work linked to Sirlin and van Ritbergen. Results were presented at conferences such as the International Conference on High Energy Physics, Particle Physics Workshop, and meetings organized by the American Physical Society and European Physical Society. Key publications appeared in journals including Physical Review Letters, Physical Review D, and Physical Review C, with citation and peer commentary from authors linked to Thomas Kinoshita, Andrzej Czarnecki, Kirill Melnikov, Aleksey Manohar, and Martin B. Wise.
Governance included a spokesperson, executive board, institutional board, and working groups for detector, beamline, electronics, and analysis—roles mirrored in collaborations like ATLAS, CMS, BaBar, Belle, and MINOS. Membership spanned professors, postdoctoral researchers, graduate students, and engineers from universities including University of California, Berkeley, Massachusetts Institute of Technology, Princeton University, Harvard University, Columbia University, University of Michigan, Cornell University, University of Pennsylvania, Duke University, Johns Hopkins University, and international institutions such as University of Tokyo and University of Melbourne. Technical coordination involved laboratory groups at Fermilab, Brookhaven National Laboratory, Paul Scherrer Institute, and electronics collaborators from SLAC National Accelerator Laboratory.
The precision measurement influenced determinations of electroweak parameters, constrained beyond-Standard Model (particle physics) scenarios studied by theorists at CERN, Institute for Advanced Study, Perimeter Institute, and DESY, and provided benchmark calibration data for experiments like Muon g−2 experiment and Mu2e. Instrumentation developments informed detector designs at DUNE, LHCb, and neutrino detector projects at SNOLAB. Alumni from the collaboration joined collaborations at ATLAS, CMS, Belle II, J-PARC, and national laboratory programs, carrying forward techniques in timing, digitization, and systematic control. The work remains cited in precision electroweak compilations by groups at Particle Data Group and reviews by researchers associated with PDG (Particle Data Group) and others.
Category:Particle physics collaborations