... on the web since 1992


FreeHEP is a "virtual organization" created in 1991 to foster collaboration in software development across different High-Energy Physics laboratories and universities. At its kickoff FreeHEP developed one of the first databases interfaced to the then nascent "World-Wide-Web". Today the main thrust of FreeHEP is the development of open-source software for data analysis and visualization, using mainly Java and C++. Although still developed primarily for use in High Energy, Nuclear and Astro- physics, much of the software is general enough to find uses well beyond these fields.

We welcome anyone from inside the physics/academic community or beyond to work with us.

The FreeHEP web and CVS servers are currently located at Stanford Linear Accelerator Center (SLAC) and are supported in part by the SLAC computing community.

Major Projects

Java Library

The goal of the FreeHEP Java library is to encourage the sharing and reuse of Java code for data analysis and visualization. Although the library is quite large, we strive to keep the dependencies between various packages in the FreeHEP library to a minimum, so you can use which ever parts interest you without being forced to use the entire library. The FreeHEP Java library is an "Open Source" library distributed under the terms of the LGPL. Many of the components of the projects described above live in the FreeHEP Java library.


A modular data mining and data visualization framework. JAS combines many of the other components of FreeHEP, including AIDA, HepRep and WIRED into a general purpose, graphical data analysis tool. The modular design of JAS3 allows components to be added and removed to customize it for use in variety of different areas.

WIRED - WWW Interactive Remote Event Display

A general purpose event visualization framework.

HepRep - HEP Representables for Event Display

HepRep forms the central part of a complete generic interface for client-server event displays. HepRep provides an insulating layer between the event-server and the event-display client, making it possible to use different HepRep clients with the same server. The WIRED and FRED event displays are two such HepRep clients.

AIDA - Abstract Interfaces for Data Analysis

The goals of the AIDA project are to define abstract interfaces for common physics analysis objects, such as histograms, n-tuples, fitters, IO etc. The AIDA project defines only abstract interfaces, to use AIDA you must use an AIDA compliant analysis application. JAS3 and JAIDA are such applications hosted as part of FreeHEP, others include Anaphe/Lizard and OpenScientist.

Lelaps - Fast Detector Simulation

Lelaps  is a fast detector simulation program plus a number of C++ class libraries, the most important one being CEPack, the main simulation tool kit. Main programs (lelapses) have been written for BaBar and for LCD (LDMar01, SDJan03 and SDMar04 are implemented).

YaPPI - Yet another Particle Property Interface

An XML based interface to the Particle Properties data book. Not under active development at present.

FreeHEP database of HEP software

The original FreeHEP database of HEP software still exists, but sadly has not been kept up-to-date. A project to generate a more modern replacement is currently on hold for lack of manpower.