SUSY Les Houches Accord

SUSY Les Houches Accord
Name	SUSY Les Houches Accord
Abbreviation	SLHA
Subject	High-energy physics data format
First issued	2003
Developers	Les Houches workshop participants
Location	Les Houches, France

SUSY Les Houches Accord

The SUSY Les Houches Accord is a community-standard data exchange format developed to communicate supersymmetric particle spectrum, parameter, and decay information among computer codes used in high-energy physics. It was formulated by participants from institutions such as CERN, DESY, SLAC National Accelerator Laboratory, Fermi National Accelerator Laboratory, and universities attending the Les Houches workshop, and has influenced tools used at facilities like Large Hadron Collider operations and analyses from experiments including ATLAS (experiment), CMS (experiment), and LHCb experiment.

History

The Accord emerged from collaborative discussions at the Les Houches Workshops involving theorists and experimentalists connected to projects at Institut Laue–Langevin, CEA Saclay, University of Oxford, Massachusetts Institute of Technology, and Princeton University. Early contributors included groups affiliated with Harvard University, University of Cambridge, University of California, Berkeley, Imperial College London, and University of Tokyo, seeking interoperability between spectrum generators such as SOFTSUSY, SPheno, and ISAJET and event generators like PYTHIA, HERWIG, and MadGraph. Subsequent revisions were motivated by results from collaborations at Tevatron, HERA, and tests against predictions related to frameworks from Minimal Supersymmetric Standard Model implementations and studies influenced by seminars at Institute for Advanced Study and Perimeter Institute for Theoretical Physics.

Purpose and Scope

The Accord defines a standardized ASCII-based format to permit exchange of supersymmetric spectra, input parameters, model definitions, and decay tables among codes developed at places such as Brookhaven National Laboratory, University of California, Santa Cruz, University of Michigan, University of Chicago, and Columbia University. It aims to reduce integration friction between spectrum calculators, renormalization group evolution tools, Monte Carlo generators, and detector simulation packages used by groups from Fermilab, CERN Theory Division, Kavli Institute for Theoretical Physics, and Max Planck Institute for Physics. The scope covers model-parameter blocks, mass spectra, mixing matrices, and decay branching ratios relevant for analyses pursued by teams at Lawrence Berkeley National Laboratory, Los Alamos National Laboratory, RIKEN, and National Institute for Nuclear Physics (INFN) collaborations.

Format and File Structure

The file structure prescribes plain-text blocks with labeled sections inspired by conventions used in software suites developed at Ohio State University, University of Washington, Johns Hopkins University, Yale University, and University of Pennsylvania. Each file includes header metadata referencing authors from institutions like University of Illinois Urbana-Champaign, University of Toronto, Seoul National University, Australian National University, and Ecole Polytechnique and uses fixed-keyword blocks for exchanges compatible with data pipelines at European Organization for Nuclear Research, KEK, and Joint Institute for Nuclear Research. The format fosters parsing by scripting languages developed at Los Alamos, Argonne National Laboratory, École Normale Supérieure, University of Edinburgh, and University of Amsterdam.

Parameter Blocks and Conventions

Parameter blocks encode inputs such as gauge couplings, soft-breaking terms, and fermion masses following conventions debated at meetings attended by delegates from Princeton Plasma Physics Laboratory, Brookhaven, Rutherford Appleton Laboratory, TRIUMF, and CEA. Block names and numerical conventions align with practices in codebases from University of Hamburg, University of Bonn, TU Munich, University of Paris, and University of Rome. The Accord specifies indexing, unit conventions, and complex-phase handling to ensure consistency with spectrum predictions produced by groups at University of Maryland, Rutgers University, University of Minnesota, University of Pittsburgh, and Stony Brook University.

Spectrum and Decay Information

Mass spectra and mixing matrix entries are provided in dedicated blocks so that decay calculators and event simulators at CERN Experimental Physics Division, Fermilab Detector Division, DESY Zeuthen, YITP Kyoto, and NIKHEF can reliably construct particle lists. Decay tables give total widths and branching ratios compatible with generator interfaces used by MadEvent, Sherpa, Calchep, and analysis frameworks developed at Korea Institute for Advanced Study, Indian Institute of Science, Tata Institute of Fundamental Research, and University of Melbourne. The approach enables cross-validation against results from collaborations with ties to SLAC, LBL, Indiana University, University of Wisconsin–Madison, and University of Florida.

Interfaces and Implementation

Implementations exist in a wide range of tools produced by groups at Cambridge University, Osaka University, Seville University, University of Barcelona, and Peking University. Interfaces map the Accord’s blocks into internal data structures for spectrum generators, likelihood calculators, and detector-simulation chains used by researchers at ETH Zurich, University of Bern, University of Geneva, Stockholm University, and Uppsala University. Bindings and parsers have been contributed by teams from University of California, Santa Barbara, University of Liverpool, University of Manchester, Universidad Nacional Autónoma de México, and Pontifical Catholic University of Chile.

Adoption and Impact in the Community

The Accord’s adoption facilitated reproducibility and cross-tool comparison across collaborations such as ATLAS, CMS, International Linear Collider community, Belle II experiment, and IceCube Neutrino Observatory analysis groups. It shaped downstream standards discussed at workshops hosted by European Physical Society, American Physical Society, International Conference on High Energy Physics, Lepton-Photon Symposium, and Les Houches Summer School and influenced software ecosystems maintained by consortia at CERN Openlab, HEP Software Foundation, Open Science Grid, and Worldwide LHC Computing Grid. The widespread use across laboratories including Fermilab, DESY, KEK, and universities worldwide underscores its role in coordinating theoretical predictions with experimental searches coordinated by groups in particle physics networks.

Category:High energy physics