Development of a more accurate Geant4 quantum molecular dynamics model for hadron therapy

Area of Science:

• Nuclear Physics
• Medical Physics
• Computational Physics

Background:

• The Quantum Molecular Dynamics (QMD) model is crucial for simulating heavy-ion therapy but shows discrepancies with experimental data regarding fragment production.
• Accurate prediction of fragment yields is essential for optimizing heavy-ion therapy dosimetry.

Purpose of the Study:

• To improve the accuracy of fragment production in water phantoms within the Geant4 simulation toolkit.
• To develop a more precise QMD model by integrating modern Skyrme interactions and an alpha-cluster model.

Main Methods:

• Implemented modern Skyrme interaction parameter sets and an ad hoc alpha-cluster model into the QMD framework.
• Utilized multi-objective optimization (MOO) with squared Mahalanobis distance to quantitatively compare simulated and experimental fragment yields and angular distributions.
• Optimized key parameters: cluster discrimination radius (R) and Gaussian packet standard deviation squared (L).

Main Results:

• The SkM*α model, combining Skyrme parameters and the alpha-cluster model, significantly improved light fragment yields in water.
• The model accurately reproduced the kinetic energy distribution of produced fragments.
• Optimized parameter L in SkM*α was validated through ground-state charge radii analysis.

Conclusions:

• The developed QMD model (SkM*α) offers a substantial improvement in simulating fragment production for heavy-ion therapy.
• The multi-objective optimization framework effectively validates nuclear models.
• This enhanced QMD model is expected to increase the precision of heavy-ion therapy dosimetry.