SLHA

SLHA
Name	SLHA
Author	Peter Skands et al.
Released	2003
Latest release	2009 (SLHA2)
Genre	data interchange standard
License	informal specification

SLHA SLHA is a textual interchange format widely used in high-energy physics for sharing supersymmetric model parameters among spectrum generators, Monte Carlo event generators, and phenomenology tools. It bridges tools developed by collaborations such as CERN, DESY, Fermilab, KEK, and groups associated with LHCb, ATLAS, CMS, and ILC studies, enabling consistent comparisons between calculations from authors like Peter Skands, Howard Baer, and collaborators. The format complements other standards adopted by projects tied to Les Houches Accord activities and by working groups convened around Snowmass and HEPData exchanges.

Introduction

SLHA provides a plain-text, human-readable representation for model inputs and outputs used by packages such as ISAJET, SOFTSUSY, SPheno, FeynHiggs, SuSpect, MicrOMEGAs, DarkSUSY, and CalcHEP. Designed in the context of community efforts hosted at venues like Les Houches Workshop and coordinated by researchers affiliated with institutions including Oxford University, University of Cambridge, Stockholm University, IPPP, and INFN, the specification emphasizes portability between platforms from Linux clusters at CERN to workstations at SLAC and Brookhaven National Laboratory.

History and Development

The specification emerged from discussions during Les Houches workshops where authors of spectrum calculators and event generators including those from PYTHIA and HERWIG sought interoperable conventions. Early contributors and proponents had ties to research groups at University of Bonn, University of Minnesota, University of California, Santa Cruz, and University of Barcelona. Subsequent iterations addressed input/output harmonization prompted by results reported at conferences such as ICHEP and Moriond, and incorporated feedback from collaborations publishing in journals like Physical Review D and Journal of High Energy Physics.

Purpose and Scope

SLHA standardizes how parameters such as soft-breaking masses, trilinear couplings, gauge couplings, and mixings are exchanged between tools developed by teams from KTH Royal Institute of Technology, LPNHE, CEA Saclay, and Institute for Theoretical Physics, Heidelberg. It enables consistent interpretation of benchmark scenarios discussed at meetings of the SUSY Working Group, the Dark Matter Working Group, and analysis groups associated with Higgs Cross Section Working Group. While focused on supersymmetric models, SLHA’s conventions interact with calculations produced by frameworks like MadGraph, Sherpa, Whizard, and codes used by researchers at University of Tokyo and Tsinghua University.

File Format and Conventions

An SLHA file is organized into named blocks, each delineated by identifiers recognizable by parsers used in packages from Max Planck Institute for Physics and Institut de Physique Théorique. Conventions cover units, numeric precision, and comment conventions adopted by authors with affiliations to LAPTH, CEA, KEK, and NIKHEF. The format uses indexed entries and matrix layouts compatible with input schemas expected by tools developed at University of Heidelberg, CERN Theory Division, and University of Wisconsin–Madison, and is often processed alongside Les Houches Event files produced by MCFM and POWHEG-based chains.

Common Blocks and Parameters

Typical blocks include mass spectra, mixing matrices, decay widths, and low-energy observables referenced in phenomenology studies from collaborations at INFN Bologna, Universidad de Granada, Princeton University, Yale University, and Rutgers University. Parameters exchanged include gaugino masses, scalar mass matrices, Yukawa couplings, and Higgs-sector parameters used in analyses published by groups at University of Manchester, University of Edinburgh, University of Bonn, and SISSA. Blocks for neutrino-related entries and CP-violating phases were extended following discussions involving teams from Institute for Nuclear Research (INR), University of Padua, and Universidad Autónoma de Madrid.

Implementations and Software Support

Most spectrum generators such as SOFTSUSY, SPheno, and SuSpect implement SLHA input/output, while event generators including PYTHIA and HERWIG read SLHA files to configure particle properties during simulations used by ATLAS and CMS analyses. Dark matter tools like MicrOMEGAs and DarkSUSY parse SLHA blocks for relic-density and detection-rate computations presented at conferences such as Neutrino and TAUP. Analysis frameworks and plotting tools at institutions like CERN and DESY provide utilities to convert between SLHA and other formats adopted by collaborations such as Belle II and LHCb.

Extensions and Revisions

SLHA2 and later community-driven proposals expanded support to include R-parity violation, flavor violation, and CP violation debated at workshops hosted by Les Houches, IPPP, and MCTP. Further extensions have been motivated by results from experimental collaborations including ATLAS, CMS, LHCb, and by theoretical developments communicated through preprints on arXiv and seminars at Perimeter Institute and KITP. Contributions to the format arise from researchers at universities and institutes such as University of California, Berkeley, Columbia University, University of Texas at Austin, and University of Chicago, reflecting broad international adoption.

Category:High energy physics software