Thursday 20 March 2025
Scientists have been trying to crack the code of cosmic rays for decades, and a recent experiment has shed new light on these mysterious particles. Cosmic rays are high-energy particles that bombard the Earth from space, but what exactly causes them is still unclear.
The latest study used a unique technique called momentum bracketing to isolate individual muons – a type of cosmic ray – and measure their energy with unprecedented accuracy. Muons are essentially heavy electrons that zip through matter at nearly the speed of light, making them ideal for studying high-energy phenomena.
To achieve this feat, researchers built a special detector called COSMOSS, which consisted of a plastic scintillator tile wrapped in aluminum foil to enhance light reflectivity. The scintillator emitted a burst of photons when hit by a muon, which were then detected by a silicon photomultiplier (SiPM). The SiPM converted the photons into an electrical signal that was read out by an oscilloscope.
The experiment took place at CERN’s East Area, where a beamline produced a high-energy particle stream. By adjusting the energy of the particles and using Cherenkov counters to filter out unwanted particles, researchers were able to create a ‘pure’ muon beam with varying energies.
The COSMOSS detector was placed in the path of the muon beam, and its response was measured for different energy ranges. The results showed that there was no significant correlation between the muon’s energy and the scintillator’s signal amplitude or area – a finding that has important implications for our understanding of cosmic rays.
One possible explanation is that the probabilistic nature of ionization, which describes how particles interact with matter, dominates at high energies. This means that even if a muon has more energy, its chances of interacting with the scintillator in a particular way are still governed by chance.
Another surprising discovery was the temperature sensitivity of the SiPMs used in the experiment. As the detector cooled down to -78°C, the signal amplitude increased, and the probability of afterpulsing (a phenomenon where the SiPM emits additional signals) seemed to rise too. This has significant implications for the use of SiPMs in future experiments.
The momentum bracketing technique developed by researchers holds great promise for improving our understanding of cosmic rays and high-energy particles. By isolating individual muons and measuring their energy with greater accuracy, scientists can gain valuable insights into the fundamental forces that govern the universe.
Cite this article: “Unlocking the Secrets of Cosmic Rays: A Breakthrough in Particle Detection”, The Science Archive, 2025.
Cosmic Rays, Muons, Momentum Bracketing, Cern, East Area, Scintillator, Silicon Photomultiplier, Cherenkov Counters, Ionization, Probabilistic Nature
