Muon hits in our detector
Muons are elementary particles produced in the Earth's atmosphere from the interaction of cosmic rays with atomic nuclei. Traveling at speeds close to that of light, they can cross great distances before decaying — which allows us to study them both at high altitudes and at sea level. Consequently, CELESTE is able to detect them at its measurement station in a way quite similar to the following:
Simulated data, not based on experimental measurements. It is merely a representation of real detection.
In our code, we simulate the passage of these particles through a detector composed of four scintillator layers (L1, L2, L3, and L4) – similar to ours! Each layer acts as a "sensor" that records the muon's passage when it crosses its surface. The goal is to visualize how these particles interact with the detector and how many layers they manage to cross.
The simulation generates cosmic muons with an angular distribution that follows the cos²(θ) law, characteristic of particles from atmospheric showers — that is, more muons come from directions close to the zenith angle (vertical) than from shallow angles.
When a muon crosses a scintillator layer, an electrical signal is produced — graphically represented as a red dot. If it crosses two layers, we have two dots, and so on. The animation shows us these events in real time, with muons represented by blue trails and hits (detections) by red dots.
The bar chart on the side tracks the detection statistics in real time, showing the percentage distribution of events with 1, 2, 3, or 4 hits. This histogram reveals important information about:
- Detector efficiency: how many generated muons are effectively detected by at least one layer.
- Hit distribution: how many muons cross 1, 2, 3, or 4 layers.
We observe that most detected muons cross only one or two layers, while few cross all four. This occurs due to the detector geometry and the angular distribution of muons — particles with more inclined trajectories tend to cross more layers, but they are also more likely to escape through the sides!
The total detection efficiency — the ratio between detected and generated muons — gives us a direct measure of the system's capability.
If you want to learn how to create this graph, check out the guide Atividades práticas / Aprendendo a programar com python: como fazer... / O gráfico dos hits do múon em nosso detector and see the code used for the simulation!