Amsler, C., Breuker, H., Bumbar, M. et al. Antiproton annihilation at rest in thin solid targets and comparison with Monte Carlo simulations. arXiv preprint arXiv:2407.06721v2 (2024).
This study investigates the mechanism of antiproton-nucleus annihilation at rest by measuring charged particle multiplicities and energy deposits from antiproton annihilations on carbon, molybdenum, and gold targets. The research aims to compare these experimental results with predictions from various Monte Carlo simulation models (Geant4 and FLUKA) to assess their accuracy in describing this complex nuclear process.
The researchers utilized slow-extracted antiprotons from the ASACUSA apparatus at CERN, annihilating them on thin solid targets of carbon, molybdenum, and gold. They employed a combination of a cylindrical hodoscope and a Timepix3 pixel detector to measure the charged particle multiplicities and energy deposits from the annihilation events. The experimental data were then compared to simulations performed using different physics lists available in Geant4 (QGSP BERT CHIPS, FTFP BERT EMY, FTFP INCLXX EMZ) and FLUKA (fluka 4-2.1) to evaluate their agreement with the observed results.
The study revealed significant discrepancies between the experimental measurements and the predictions of all four Monte Carlo simulation models tested. While FLUKA, CHIPS, and INCL showed better overall agreement compared to FTFP, none of the models could accurately reproduce the experimental distributions for all three target materials. The discrepancies were particularly pronounced in predicting the multiplicities of minimum ionizing particles (MIPs), primarily charged pions, detected by the hodoscope, with the disagreement increasing with the target's atomic mass.
The study concludes that current Monte Carlo simulation models, despite their sophistication, still struggle to fully capture the intricacies of antiproton-nucleus annihilation at rest. The observed discrepancies highlight the limitations of existing models in accurately predicting the types and distributions of particles produced in these annihilations, particularly for heavier nuclei. The authors emphasize the need for further refinement of these models, incorporating a more comprehensive understanding of the underlying physics, especially at low energies.
This research holds significant implications for various fields, including nuclear physics, particle physics, and antimatter studies. Accurate modeling of antiproton-nucleus annihilation is crucial for experiments at CERN's Antiproton Decelerator (AD) that rely on these simulations to understand their detection efficiencies and background processes. The findings highlight the need for improved simulation tools to accurately interpret experimental data and advance our understanding of antimatter interactions with matter.
The study acknowledges limitations in precisely identifying heavier fragments beyond broad categorization due to the detectors' limitations. Future research using more sophisticated detectors capable of better particle identification is suggested. Additionally, the authors recommend further investigations focusing on low-energy antiproton annihilations to provide crucial data for validating and refining existing simulation models.
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by Claude Amsle... at arxiv.org 10-10-2024
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