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News Introduction The HistFitter Group Acknowledgements

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News

• March 2015: The HistFitter publication is accepted by EPJC.

• March 2015: Tutorial at DESY

Introduction

A software framework for statistical data analysis, called HistFitter, is presented here.

HistFitter has been used extensively by the ATLAS Collaboration to analyze big datasets originating from proton-proton collisions at the Large Hadron Collider at CERN. Since 2012 HistFitter has been the standard statistical tool in searches for supersymmetric particles performed by ATLAS. HistFitter is a programmable and flexible framework to build, book-keep, fit, interpret and present results of data models of nearly arbitrary complexity.
It extends existing statistics tools in four key areas:

Programmable framework: HistFitter performs complete statistical analyses of pre-formatted input data samples, from a single user-defined configuration file, by putting together tools from several sources in a coherent and programmable framework.

Analysis strategy: HistFitter has built-in concepts of control, signal and validation regions, which are used to constrain, extrapolate and validate data model predictions across an analysis. The framework also introduces a statistically rigorous treatment of the validation regions.

Bookkeeping: HistFitter can keep track of numerous data models, including all generated input histograms, both before and after adjustment to measured data, and can perform statistical tests and model-parameter scans of all these models in an organized way. This introduces a powerful additional level of abstraction, which aids the processing of large collections of signal hypothesis tests.

Presentation and interpretation: HistFitter provides a collection of methods to determine the statistical significance of signal hypotheses, estimate the quality of likelihood fits, and produce publication-quality tables and plots expressing these results.

The HistFitter Group

The HistFitter group are:

• Max Baak (CERN, Switzerland)
• Geert-Jan Besjes (Niels Bohr Institute, University of Copenhagen, Denmark)
• David Côté (University of Texas, USA)
• Alex Koutsman (TRIUMF, Canada)
• Jeanette Lorenz (LMU/Excellence Cluster Universe, Germany)
• Dan Short (University of Oxford, UK)

Acknowledgements:

We are grateful to the RooFit, RooStats, and HistFactory authors for a fruitful collaboration and useful feedback, in particular to Kyle Cranmer, Lorenzo Moneta and Wouter Verkerke.

We like to thank the ATLAS collaboration and its SUSY physics group for useful discussions and suggestions for the development of HistFitter. We are specifically grateful to following members of the ATLAS SUSY physics group for their support and contributions to the development of HistFitter: Andreas Hoecker, Till Eifert, Zachary Marshall, Emma Sian Kuwertz, Evgeny Khramov, Sophio Pataraia and Marcello Barisonzi.

For graphical support and development we extend our gratitude to Solkin Keizer.
We also kindly thank the Gfitter group for using their web page style.

This work has been supported by:

• CERN, Switzerland;
  
• The DFG cluster of excellence "Origin and Structure of the Universe", Germany;
  
• The Natural Sciences and Engineering Research Council of Canada and the ATLAS-Canada Subatomic Physics Project Grant, Canada;
  
• The Department Of Energy and the National Science Foundation of the United States of America, United States of America;
  
• FOM and NWO, the Netherlands;
  
• STFC, United Kingdom.