Understanding Baryon Production in Calorimeters for High-Energy Physics: Insights from Monte Carlo Simulations

Calorimetry is one of the principal tools for investigating nature in the field of high-energy physics. This process operates by colliding particles on a calorimeter, a specialized detector designed to fully absorb the incoming particles. This collision initiates a cascade of particles, forming a shower that emits charge or light as it traverses the calorimeter material. This transfer of energy from particle momenta to charge or light signals allows for the precise calculation of the shower’s total energy.

The effectiveness of a calorimeter hinges on the type of material that is chosen. On one hand, it needs to be dense enough to stop the particles fully. On the other hand, a material that releases too many baryons from a collision can introduce noise and ‘invisible’ energy that eludes detection. This study centers on the intricate interplay between incoming particles and calorimeter materials.

Employing Monte Carlo simulations with GEANT4 (a particle physics simulation toolkit), we subjected an array of particles to various calorimeter materials, unveiling some of the mechanisms behind baryon production. Our analysis reveals that the primary source of baryon production stems from the “evaporation” of the calorimeter material nucleus upon collision, liberating protons and neutrons. This happens at relatively low beam energies of around 5 GeV. A much smaller effect is the pair production of baryons in inelastic collisions.

We also found the unaccounted “invisible” energy in the calorimeter to be proportional to the number of baryons produced. This suggests that at least part of this invisible energy arises from the binding energy in the nucleus being overcome as the nucleus evaporates into its substituent parts. This binding energy then does not appear as light or charge signals in the calorimeter, justifying the name ‘invisible’ energy.

Extending our investigations across various materials, we found the Baryon production to increase notably with the atomic number of the material. This is consistent with the proton and neutron production through nucleus evaporation described above.