[Paper Review] SpartyJet 4.0 User's Manual

P. A. Delsart, K. Geerlings+3 more|arXiv (Cornell University)|Jan 17, 2012

Particle physics theoretical and experimental studies19 references3 citations

TL;DR

SpartyJet 4.0 is a ROOT-based software framework that extends the FastJet library with a Python interface, modular jet analysis tools, and a graphical browser for interactive jet physics analysis. It enables users to perform jet finding, measure jet and event moments, and visualize results via a GUI, with support for multiple input formats and configurable output in ROOT TTree format.

ABSTRACT

SpartyJet is a set of software tools for jet finding and analysis, built around the FastJet library of jet algorithms. SpartyJet provides four key extensions to FastJet: a simple Python interface to most FastJet features, a powerful framework for building up modular analyses, extensive input file handling capabilities, and a graphical browser for viewing analysis output and creating new on-the-fly analyses. Many of these capabilities rely on a ROOT-based backend. Beyond finding jets, many jet tools in SpartyJet perform measurement of jet or event variables, available to subsequent tools and stored in the final output. SpartyJet can be downloaded from HepForge at http://projects.hepforge.org/spartyjet.

Motivation & Objective

• To provide a user-friendly, modular framework for jet finding and analysis in high-energy physics.
• To extend the FastJet library with a Python interface and advanced analysis tools for jet and event moment measurements.
• To enable interactive exploration of jet analysis results through a graphical browser with on-the-fly analysis capabilities.
• To support diverse input formats (e.g., HepMC, Pythia, StdHEP) and flexible output configuration for ROOT-based analysis.
• To streamline the development and visualization of jet physics workflows using a unified, extensible software environment.

Proposed method

• Uses the FastJet library as the core jet finding engine, with custom wrappers to expose its algorithms via a Python interface.
• Employs a modular JetBuilder framework where jet analyses are constructed as chains of JetTool components (e.g., finders, selectors, transformers, moment tools).
• Supports multiple input formats through dedicated input makers (e.g., NtupleInputMaker, HepMCInput, PythiaInput) that auto-detect file types by extension.
• Configures output via a TTree in a ROOT file, with customizable variable types (float/double) and storage of jet constituents using index-based mapping.
• Integrates a graphical interface launched via the `sparty` command, enabling real-time visualization of event-by-event and full-run plots.
• Enables on-the-fly analysis through a live algorithm facility that dynamically constructs and applies tools using user-provided parameters.

Experimental results

Research questions

• RQ1 How can a high-level, modular framework be designed to simplify jet analysis while maintaining compatibility with established libraries like FastJet?
• RQ2 What is the most effective way to integrate interactive visualization and on-the-fly analysis into a high-energy physics software stack?
• RQ3 How can diverse input formats be abstracted into a uniform interface to streamline data ingestion for jet analysis?
• RQ4 What configuration options are necessary to support flexible output of jet and event moments in a standard, analyzable format?
• RQ5 To what extent can a GUI-based environment enhance the exploration and validation of jet physics results without requiring custom ROOT scripting?

Key findings

• SpartyJet 4.0 successfully provides a Python-based interface to FastJet, enabling rapid prototyping and modular jet analysis workflows.
• The framework supports multiple input formats including HepMC, Pythia, and StdHEP, with automatic detection based on file extension.
• Output is stored in a configurable ROOT TTree with branches for jet properties (e.g., pt, eta, phi, mass), event moments, and constituent indices.
• The graphical interface allows real-time visualization of jet distributions and on-the-fly analysis using TTree::Draw syntax and TCut filters.
• Constituent mapping is preserved via `MyJet_ind` and `MyJet_numC` arrays, enabling detailed reconstruction-level analysis of jet structure.
• The system enables interactive exploration of jet dynamics, including ratio measurements like τ3/τ2, through user-defined moment plots in the GUI.