CMS Open Data Visualization with FireworksWeb

In the heart of particle physics, where scientists smash atoms together to understand the fundamental building blocks of the universe, there exists a critical tool for making sense of the chaos: the event display. When particles collide inside a massive machine like the Large Hadron Collider, they create a fleeting spray of new particles that fly out in every direction. These particles leave behind traces in layers of detectors, much like footprints in the snow. To study these collisions, physicists need to see these footprints all at once, in three dimensions, to understand how the particles moved and interacted. For decades, this has been done using specialized software that must be installed on a powerful computer, requiring the user to be a trained expert just to open the file. This barrier has kept the actual data of these world-changing experiments locked away from students, teachers, and the curious public, who could otherwise learn from the real evidence of how the universe works.

A team of researchers has now broken down that wall by turning this complex, heavy software into a simple web page. They have taken the standard tool used by professional physicists at the CMS experiment and rebuilt it to run entirely inside a modern web browser. This new system, called FireworksWeb, allows anyone with an internet connection to look at real collision data from the Large Hadron Collider without installing any programs or having a background in physics. The system works by keeping the heavy mathematical processing on a powerful server at CERN, which then sends a lightweight, interactive picture to the user's computer. The user can rotate the view, zoom in on specific particles, and filter what they see, all while the server does the hard work of calculating the paths of the particles through magnetic fields. This shift means that the rich, three-dimensional data of high-energy physics is now as accessible as a website, opening the door for education and public engagement in a way that was previously impossible.

The journey to this point began more than fifteen years ago, when the original software was a desktop program that required specific computer hardware and complex installations. As technology changed, particularly with the rise of web browsers and the need for remote collaboration, the old system became difficult to maintain and share. The researchers realized that to share the CMS Open Data—a vast collection of real collision events made available to the public—they needed a new approach. They rebuilt the system from the ground up, creating a version where the server handles the physics and the browser handles the display. This architecture allows the system to run on any device with a modern browser, from a laptop to a tablet, removing the need for local software installation entirely. The result is a tool that is robust enough for professional use in the control room of the CMS experiment, where it is currently used to monitor live data, yet simple enough for a student to use with a single click.

Inside this web-based display, the visualization is designed to be both precise for experts and clear for beginners. The system can show millions of tiny details, such as the hexagonal prisms that make up the High-Granularity Calorimeter, a detector component that measures the energy of particles. To render this massive amount of data smoothly, the software uses a specialized rendering engine that groups identical shapes together, allowing the browser to handle over a million individual pieces without slowing down. Users can switch between different views, including standard side-on and top-down perspectives, as well as specialized views that compress the outer edges of the detector to fit the entire machine into a single frame. This "fish-eye" effect allows a viewer to see the inner core of the collision and the outer layers of the detector simultaneously, providing a complete picture of the event's structure.

Beyond just looking at the data, the system includes powerful tools for exploring it. Users can filter the display to show only specific types of particles, such as muons or jets, or to hide certain layers of the detector to see what lies beneath. The system also remembers the user's settings, so a specific view can be saved and shared as a simple link. When someone clicks that link, they see the exact same perspective, with the same filters and camera angle, allowing for easy collaboration and teaching. This capability is particularly important for the Open Data project, where the goal is to let anyone, anywhere, explore the same datasets. The system connects directly to the CERN storage servers, streaming the data on demand so that users do not need to download huge files to their own computers.

The researchers have also taken a significant step toward making this tool universal. They developed a new way to describe the data that does not rely on the specific, complex formats used by the CMS experiment. By converting data into a compact, neutral format, the same display can now show results from different types of experiments or from simplified datasets used in education. This means that a group studying a specific type of particle decay can create their own dataset, convert it into this new format, and immediately view it in the browser without needing to install the full CMS software suite. This flexibility turns the event display into a universal window for particle physics, capable of showing data from various sources through a single, consistent interface.

Looking ahead, the team plans to expand these capabilities further as the Large Hadron Collider moves into its next phase of operation, known as the High-Luminosity LHC. This future phase will produce even more data, requiring tools that can handle increased complexity and volume. The current work lays the foundation for integrating more advanced analysis tools directly into the browser, allowing users to export their own custom views and interact with the data in deeper ways. The ultimate goal is to create a seamless environment where the boundary between professional research and public exploration disappears, allowing anyone to stand in the control room of one of the world's most sophisticated scientific instruments and see the universe in action.