Bringing CERN to classrooms: Learning about ALICE with AR and LEGO Open Access

ALICE is an experiment designed by the ALICE Collaboration to re-create the conditions in the first millionth of a second after the Big Bang.² This is done by accelerating heavy ions (such as lead) using the LHC and causing them to collide at very high energies. These collisions cause the annihilation of the heavy ions to create a plasma of fundamental particles, also known as a quark–gluon plasma. Various subdetectors that help the study of this short-lived fundamental state of matter are integrated within ALICE.

From the perspective of classrooms, this article focuses on the parts and subdetectors that are housed in the center as concentric cylindrical shells: the solenoid magnet, time-of-flight (TOF) detector (in orange), transition radiation detector (TRD; in yellow), time projection chamber (TPC; in blue), and inner tracking system (ITS; in light green). While ALICE houses various other detectors (e.g., a dipole magnet, a muon tracker, and a muon trigger), the article only discusses those that are crucial to facilitate the understanding of fundamental particle-physics principles and the overarching functionality of the detector. The solenoid magnet provides the strong magnetic field along the axis where collisions happen, and together with the dipole magnet, can bend the trajectories of charged subparticles by different amounts (depending on their momentum). These particles are first traced by the ITS, which acts as a radar system. The ITS can very precisely determine the collision point, where the particles were created, and toward which direction they are headed. The TPC then acts as a giant 3D camera in ALICE. It is filled with a special gas mixture such that when charged particles move through the TPC, they leave trails behind, which are unique to each particle. Next is the TRD, which acts as a special flashlight to detect the charged particles, particularly the electrons. The TOF detector then acts as a very precise stopwatch to measure the different times it takes the particles to travel from the collision point to the TOF detector, so that the particle velocities can be measured. Since the inception of its operations in 2008, the ALICE experiment has bridged a significant knowledge gap in the understanding of high-energy particles. The following section presents an overview of the AR application developed to visualize the ALICE detector.

In this article, we illustrate an approach to apprise students about the ALICE particle detector by combining the LEGO ALICE model with virtual visualizations using AR. The ALICE LEGO model in its compact midi version (see Fig. 1) was developed by Leo Felix as part of a student group project to design and build a 1:40 scale LEGO model of ALICE under the “Build Your Own Particle Detector” outreach program.³ This hands-on model facilitates tactile interaction, allowing students to gain a concrete understanding of ALICE and its subdetectors. To further enhance students’ comprehension of this advanced scientific instrument, we introduce an immersive visualization of ALICE using augmented reality, suitable for use on an iOS device and on the Microsoft HoloLens 2.⁴ Students can hence interact with the ALICE LEGO model as well as the virtual model using these devices. As shown in Fig. 2, the ALICE LEGO model serves as a target model, such that when students look at it through their devices, the virtual model of ALICE appears. AR thus brings the particle detector to the classroom, making it accessible for the students. The virtual and the physical model are directly connected, and the users can rotate the ALICE LEGO model to rotate the augmented model or can also walk around it.

To focus on certain subdetectors, in the iOS version, an interactive menu has been incorporated, which can be activated through a button on the screen. The menu allows users to seamlessly toggle the visibility of individual parts of the detector, enhancing the user engagement and interactivity. Each subdetector of ALICE has been further labeled (see Fig. 2), along with an additional option to click and reveal textual information, which can be enabled through toggle buttons. These buttons then enable an exclusive view of the individual subdetectors with explanations (see Fig. 3). It is also possible to use the application with Microsoft HoloLens 2. Using the smart glasses enables interaction with the display menu and the subdetectors through hand gestures.

This application illustrates how large-scale research experiments can be adapted for teaching in such a way that learners can directly interact with the facilities. To further increase the availability of the application, along with a HoloLens 2 version, an iOS-optimized version is also available. Future studies are planned to evaluate the learning effectiveness of the application. Furthermore, we will integrate a ChatGPT interface for individual AI-based feedback support during inquiry-based learning with the environment.⁵ 

This work was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy–EXC 2094–390783311 (ORIGINS)–and the Federal Ministry of Education and Research (BMBF; Expansion of ALICE at the LHC: experiments with the ALICE detector at CERN: BMBF ErUM-FSP T01).