Physics-Audited Geant4 Modelling of 68 MeV HE–PIXE Spectra from a Cu/Bi Multilayer Target in the ARRONAX Geometry

HE–PIXE, Geant4, ARRONAX, Cu/Bi multilayer, HPGe detector, photon provenance, Monte Carlo modelling

Mostafa Ragheb1*,
Mail: mostafa.ragheb@ul.edu.lb
Orcid Id: 0009-0003-6977-9243, Arts,
Sciences and Technology University in
Lebanon (AUL), Beirut, Lebanon.

Diana el hajjar Ragheb2,
Mail: Diana.elhajjar@ul.edu.lb
Orcid Id: 0009-0009-3996-0512, Department of
Physics, Faculty of Sciences, Lebanese
University, Tripoli, Lebanon

Monzer Alwan3.
Mail: Monzer.alwan@ul.edu.lb
Orcid Id: 0009-0009-5680-2962, Department of
Physics, Faculty of Sciences, Lebanese
University, Tripoli, Lebanon

Rafic Merhej4.
Mail: Rafic_merhej@hotmail.com
Orcid Id: 0009-0002-2417-5393, Department of
Physics, Faculty of Sciences, Lebanese
University, Fanar, Lebanon

Firas Hijazi5,
Mail: Firas.hijazi@ul.edu.lb
Orcid Id: 0009-0006-7053-7825, Department of
Physics, Faculty of Sciences, Lebanese
University, Beirut, Lebanon

Ali Jaafar6,
Mail: ali.jaafar.3@ul.edu.lb
Orcid Id: 0009-0004-0655-145X, Department
of Physics, Faculty of Sciences, Lebanese
University, Beirut, Lebanon

Received:23-06-2026
Revised:28-07-2026
Accepted:05-08-2026

European Journal of Prosthodontics and Restorative Dentistry (2026) 34(7s), 779–796

Physics-Audited Geant4 Modelling of 68 MeV HE– PIXE Spectra from a Cu/Bi Multilayer Target in the ARRONAX Geometry

A Geant4 model was developed for the published ARRONAX high-energy particle-induced X-ray emission (HE–PIXE) benchmark using a 68 MeV pro-ton beam and a Cu/Bi multilayer target. The model combines low-energy electromagnetic transport, atomic relaxation, hadronic interactions, explicit air and detector-window attenuation, and an event-level photon-audit system that records the creator process, origin material and volume, exit layer, direction, energy, and statistical weight. The processed simulation was compared with a digitized experimental targetminus-background spectrum over the interval 5–90 keV. For the nor-malized spectral-shape comparison, the archived analysis output gave RMSE = 0.0610359, MAE = 0.0202528, Pearson correlation r = 0.625858, and R2 = 0.253298. These metrics quantify spectral-shape agreement only and do not estab-lish absolute X-ray yield because beam charge, acquisition live time, and a calibrated absolute detector efficiency were unavailable from the digitized benchmark. The audit contained 15,834 accepted photon records. The weighted creator-process contribution was dominated by hadron ionisation (74.5484%), followed by proton-inelastic production (11.0080%), electron ion-isation (7.2502%), and electron bremsstrahlung (6.3660%). The results demonstrate the diagnostic value of event-level photon provenance for identifying whether discrepancies originate from production physics, target geometry, attenuation, angular acceptance, or detectorresponse pro-cessing. The work therefore provides a transparent and reproducible frame-work for HE–PIXE model assessment while clearly separating normalized spectral-shape comparison from absolute experimental validation.

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