HB2025 - the 71st ICFA Advanced Beam Dynamics workshop on High-Intensity and High-Brightness Hadron Beams

Quantifying Differences Between High-Dimensional Beam Phase Space Distributions Using f-Divergences​

WECBC02

Oct 22, 2025, 11:50 AM

20m

room C (conference center)

Contributed Oral Presentation WGE: Beam Instrumentation, beam Interaction and AI technology WECBC WGE contributed oral

Speaker

Yu Du (Institute of Modern Physics, Chinese Academy of Sciences)

Description

Quantifying differences between high-dimensional phase space distributions is essential for analyzing beam measurements and simulations. While f-divergences such as KL or JS divergence are increasingly used for this purpose, including in machine learning applications, their values lack physical interpretability. This work establishes the first physics-grounded framework for f-divergences in accelerator beam contexts. Through systematic analysis of 4D transverse phase space distributions with elliptical symmetry, we reveal how distinct f-divergences assign region-specific weights to distribution cores, tails, and halos. We also prove rigorous correspondences between f-divergence values and conventional beam physics quantities: emittance differences and mismatch factors. These results, validated by statistical analysis of synthetic distributions, provide concrete selection guidelines for f-divergences in phase space comparisons and establish assessment standards for evaluating f-divergence values in beam physics applications.