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FLAF

FLAF — the **F**lexible **LA**W-based Analysis **F**ramework — is the shared software framework behind several CMS Higgs-sector analyses at CERN. It turns CMS NanoAOD files into the analysis ntuples, histograms, plots and statistical results that go into a physics paper.

FLAF organises this work as a chain of tasks managed by LAW (the Luigi Analysis Workflow). You describe what you want (for example, "the final plots for the 2022 data"); LAW figures out which intermediate steps are needed, runs only those, and can dispatch them to the CERN HTCondor batch system.

New here? You are in the right place.

These docs assume no prior experience with LAW, Luigi or batch computing. If your background is physics rather than software engineering, start with Key terms and the Getting started track — every concept is introduced from scratch.

The big picture

FLAF is shared by three analyses — HH→bb̄ττ, HH→bb̄WW and H→μμ — which all run the same pipeline. From CMS NanoAOD to final results, the stages are:

flowchart TD
    NANO[CMS NanoAOD<br/>on DAS / WLCG] --> IFT[InputFileTask<br/>resolve the file list]
    IFT --> ATF[AnaTupleFileTask<br/>produce analysis ntuples]
    ATF --> ATM[AnaTupleMergeTask<br/>merge per dataset]
    ATM --> HTP[HistTupleProducerTask<br/>compute analysis observables]
    HTP --> HFN[HistFromNtupleProducerTask<br/>fill histograms]
    HFN --> HM[HistMergerTask<br/>merge histograms]
    HM --> HP[HistPlotTask<br/>make plots]
    HP --> STAT[Statistical inference<br/>datacards, limits, scans]

Each box is a LAW task. You normally run only the last task you care about — LAW pulls in everything upstream automatically. The whole pipeline is explained step by step in the full-workflow walkthrough.

How to read these docs

The documentation is organised so you can enter at the level you need.

What FLAF is — and is not

  • FLAF is a framework, not an analysis. It lives in the cms-flaf/FLAF repository and is included as a git submodule inside each analysis repository. You never clone FLAF on its own to run an analysis — you clone an analysis repository (which brings FLAF with it). See Architecture and Installation.
  • FLAF provides the common machinery: the task definitions, the configuration system, the environment setup, the storage abstraction and the CI. The physics specifics (which signals, which observables, which categories) live in each analysis repository and are documented there — see Analyses.

Getting help

  • Something went wrong? Check Troubleshooting first — it collects the most common pitfalls and their fixes.
  • An unfamiliar word? The Glossary translates framework vocabulary into analyst terms.
  • Found a docs problem? Use the edit icon on any page to open a pull request, or open an issue on GitHub.