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LHC Reinterpretation Forum
2023 Summary

.large.blue[Matthew Feickert]
.large[(University of Wisconsin-Madison)]
[email protected]

ATLAS SUSY Workshop 2023

September 12th, 2023


LHC Reinterpretation Forum 2023

.kol-1-2[ .large[

  • Perspectives from the 8th workshop of the Forum on the interpretation of the LHC results for BSM studies

    • First meeting of the LHC EFT Working Group with the Reinterpretation Forum
    • Multiple contributions from Belle II, working to follow reinterpretation best practices
  • Much to summarize from an engaging week of discussions with ATLAS, CMS, Belle II, and theory, but focusing on

    • Accomplishments in publishing .bold[rich HEPData and full statistical models]
    • Work towards publishing and reusing .bold[machine learning workflows] ] ] .kol-1-2[

.caption[[LHC Reinterpretation Forum 2023, IPPP Durham](https://conference.ippp.dur.ac.uk/event/1178/)] ]

HEPData gains: Full statistical models

.kol-1-2[ .huge[

  • Rich HEPData archives seen to provide useful information for theory colleagues
    • Made very clear that the information that ATLAS is providing is useful and they want to be able to cite it
  • Use of ATLAS full statistical models providing enhancement to theory recasting tools by allowing use of control regions during fits and improved combinations ] ] .kol-1-2[

.caption[[Signal region combination in CheckMATE](https://conference.ippp.dur.ac.uk/event/1178/contributions/6439/), Krzysztof Rolbiecki]

.caption[[New developments in SModelS](https://conference.ippp.dur.ac.uk/event/1178/contributions/6454/), Sabine Kraml] ]

HEPData gains: Full statistical models

.kol-1-2[ .huge[

  • Multiple theory tools are now refactoring to interface with new spey likelihood building framework
  • With full statistical models from ATLAS are able to properly handle nuisance parameters for improved combinations ] ] .kol-1-2[

.caption[[Spey: smooth inference for reinterpretation studies](https://conference.ippp.dur.ac.uk/event/1178/contributions/6436/), Jack Araz] ]

HEPData gains: Full statistical models

.kol-1-2[ .huge[

  • Multiple theory tools are now refactoring to interface with new spey likelihood building framework
  • With full statistical models from ATLAS are able to properly handle nuisance parameters for improved combinations ] ] .kol-1-2[

.caption[[Spey: smooth inference for reinterpretation studies](https://conference.ippp.dur.ac.uk/event/1178/contributions/6436/), Jack Araz] ]

HEPData gains: Full statistical models

.kol-1-2[ .large[

  • The HEP Statistics Serialization Standard (HS3) allows for more publication through HEP universal serialization to JSON
    • Goal: Write (model) once, run anywhere
  • Current draft version of HS3 available in the master branch of ROOT is being used to serialize a RooFit workspace for ongoing ATLAS analysis
    • BAT.jl implementation WIP
    • pyhf implementation planned following future development ] ] .kol-1-2[

.caption[[HEP Statistics Serialization Standard](https://conference.ippp.dur.ac.uk/event/1178/contributions/6463/), Carsten Burgard] ]

HEPData gains: Full statistical models

.kol-1-2[ .large[

  • The HEP Statistics Serialization Standard (HS3) allows for more publication through HEP universal serialization to JSON
    • Goal: Write (model) once, run anywhere
  • Current draft version of HS3 available in the master branch of ROOT is being used to serialize a RooFit workspace for ongoing ATLAS analysis
    • BAT.jl implementation WIP
    • pyhf implementation planned following future development ] ] .kol-1-2[

.caption[[HEP Statistics Serialization Standard](https://conference.ippp.dur.ac.uk/event/1178/contributions/6463/), Carsten Burgard] ]

HEPData gains: Full statistical models

.kol-1-2[ .huge[

  • Growing interest in pursuing full statistical model benefits is evident from CMS studies towards combined ATLAS+CMS top EFT
  • Tooling for bidirectional translation from HistFactory to CMS Combine model serialization with goals of simplifying ATLAS+CMS combinations ] ] .kol-1-2[

.caption[Save the EFT: a primer for the ATLAS+CMS combination in the top sector, Kirill Skovpen] ]


ML + reinterpretation: DNN profiled likelihoods

.kol-1-3[ .large[

  • While full statistical models allow for calculating the profiled likelihood during reinterpretation, the additional computation time might be traded for faster approximations for large surveys
  • Learning a DNN representation of the profile likelihood allows for speedup while maintaining sufficient accuracy ] ] .kol-2-3[

.caption[Parametrising profiled likelihoods with neural networks, Humberto Reyes-González]

.large[

  • NN model serialzed to ONNX distributed to Zenodo ] ]

ML + reinterpretation: Active learning

.kol-1-2[ .huge[

  • Linear grid search in for limit setting in parameter space is computationally intensive
  • Instead can learn the exclusion contour with active learning reducing total computing time
    • Requires intensive ML workflow though ] ] .kol-1-2[

.caption[[Active Learning](https://conference.ippp.dur.ac.uk/event/1178/contributions/6449/), Christian Weber] ]

ML + reinterpretation: Active learning

.kol-1-2[ .large[

  • ATL-PHYS-PUB-2023-010 leverages REANA to run the workflows at scale with analysis loop until contour learned ]

.caption[[ATL-PHYS-PUB-2023-010](https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PUBNOTES/ATL-PHYS-PUB-2023-010/)] ] .kol-1-2[

.caption[[Active Learning](https://conference.ippp.dur.ac.uk/event/1178/contributions/6449/), Christian Weber] ]

ML + reinterpretation: Publication of data products

.kol-1-2[ .large[

  • The "Les Houches guide to reusable ML models in LHC analyses" guidelines (forthcoming) advocates
    • As ML becomes increasingly a core part of analysis workflow also important to preserve the workflows
    • Use of open source machine learning framework
    • Serialize ML model in preservation format for inference (e.g. ONNX, lwtnn) ] ] .kol-1-2[ .large[
  • ATLAS SUSY has made two ML models public through archival on HEPData via ONNX, though publication of lwtnn files to HEPData has yet to happen

]

.caption[[Recastable ML](https://conference.ippp.dur.ac.uk/event/1178/contributions/6461/), Tomasz Procter] ]

ML + reinterpretation: Publication of data products

.kol-1-2[ .large[

  • Supplementary Material
    • Improved definitions and documentation of all input and output variables for ML model
    • Leverage .bold[validated] analysis code implementation (e.g.rivet or SimpleAnlaysis)
    • At minimum, would want a short note that could be uploaded alongside ML model serialization
  • ATLAS SimpleAnalysis and RECAST already puts these within easy reach ] ] .kol-1-2[ .large[
  • Validation Material
    • Cutflows: When cuts depend on a neural net output
    • Along with cutflows need to know exact signal models (provide SHLA files, simulation run cards)
    • Input and output plots (especially for important features) ] ]

Summary

.huge[

  • Clear advantage that ATLAS has over CMS at the moment is publication of full statistical models and rich HEPData
    • Broader community loudly wants to use it and wants to cite it when used
    • Theory community explicitly requests full statistical models continue to be published
  • ML continues to bring new approaches to reinterpretation and community recommendations
    • Les Houches guide to reusable ML models in LHC analyses guidelines
    • Across theory and experiment advantages being seen in terms of compute saving ]

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Backup


Talks from ATLAS Collaborators


Reinterpretation for unbinned measurements

.kol-1-2[ .large[

  • Inference-aware binning
    • Publish measurement, then for reinterpretation select optimal binning for analysis
  • Derivative Measurements
    • Allows later for $f(x)$ when $x$ measured
  • Extension to higher-dimensions
    • ML tools extend readily to multiple dimensions ] ] .kol-1-2[

.caption[[Using unbinned measurements for new physics](https://conference.ippp.dur.ac.uk/event/1178/contributions/6431/), Ben Nachman] ]

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The end.