ACTS Common Tracking Software

or A Common Tracking Software if you do not like recursive acronyms

ACTS is an experiment-independent toolkit for (charged) particle track reconstruction in (high energy) physics experiments implemented in modern C++.

More information can be found in the ACTS documentation.

Quick start

ACTS is developed in C++ and is built using CMake. Building the core library requires Boost and Eigen. The default C++ standard is C++23; C++20 is supported with -DCMAKE_CXX_STANDARD=20. The following commands will clone the repository, configure, and build the core library

git clone https://github.com/acts-project/acts <source>
cmake -B <build> -S <source>
cmake --build <build>

For more details, e.g. specific versions and additional dependencies, have a look at the "Building ACTS" guide. If you find a bug, have a feature request, or want to contribute to ACTS, have a look at the contribution guidelines.

Python bindings

ACTS is also available as a Python package via pip install pyacts. See the Python bindings documentation for details.

Versioning and public API

Release versions follow semantic versioning to indicate whether a new version contains breaking changes within the public API. Currently, only a limited part of the visible API is considered the public API and subject to the semantic versioning rules. The details are outlined in the versioning and public API documentation.

Repository organization

The repository contains all code of the ACTS projects, not just the core library that a physics experiment is expected to use as part of its reconstruction code. All optional components are disabled by default. Please see the "Building ACTS" guide on how-to enable them.

Folder	include path	Namespace	Python module
Core/	#include "Acts/..."	Acts::	acts
Plugins/	#include "ActsPlugins/PluginName/..."	ActsPlugins::	acts.pluginname
Fatras/	#include "ActsFatras/..."	ActsFatras::	acts.fatras
Alignment/	#include "ActsAlignment/..."	ActsAlignment::	acts.alignment
Examples/	#include "ActsExamples/..."	ActsExamples::	acts.examples
Python/	#include "ActsPython/..." (not much used)	ActsPython::	N/A
Tests/	#include "ActsTests/..." (not much used)	Acts::Tests::	N/A

Short summary of the modules and directories:

• Core/ contains all the core functionality with minimal dependencies and no framework or I/O related code
• Plugins/ contains plugins for core functionality that require additional external packages.
• Fatras/ provides fast track simulation tools based on the core library.
• Examples/ contains simulation and reconstruction examples. These are internal tools for manual full-chain development and tests.
• Tests/ contains automated unit tests, integration tests, and (micro-)benchmarks.
• Python/ contains the python bindings for the different modules
• thirdparty/ contains external dependencies that are usually not available through the system package manager.

Authors and license

Contributors to the ACTS project are listed in the AUTHORS file.

The ACTS project is published under the terms of the Mozilla Public License, v. 2.0. A copy of the license can be found in the LICENSE file or at https://mozilla.org/MPL/2.0/ .

The ACTS project contains copies of the following external packages:

• OpenDataDetector licensed under the MPLv2 license.

ACTS is a collaborative open source software project, and hence does not base its organisational structure on (intellectual) ownership of certain pieces of code by individuals. The usage of GitHub's CODEOWNERS system is currently under evaluation primarily to identify opt-in contact persons for certain parts of the code base in an attempt to simplify workflows and identify information contacts and reviewers. A detailed description of our test usage is part of the CODEOWNERS file.