Improved simulation of beam backgrounds and collimation at SuperKEKB

TL;DR

This paper presents an enhanced simulation approach for beam backgrounds at SuperKEKB, improving accuracy and efficiency, and introduces a new collimator alignment method based on simulation validation.

Contribution

The study introduces a refined simulation methodology with detailed collimator physics, collimator tip scattering, and an embedded tracking framework, addressing previous discrepancies and optimizing collimation.

Findings

Resolved discrepancies between measured and predicted background levels.

Reduced computational time for collimation system optimization.

Validated simulation accuracy through collimator aperture scans.

Abstract

Mitigation of beam backgrounds via collimators is critical for the success of the Belle~II experiment at the SuperKEKB electron-positron collider. We report on an improved simulation methodology, which includes a refined physical description of the collimators and beam pipe, our first implementation of collimator tip scattering, and in which the existing beam particle tracking software has been embedded into a new sequential tracking framework. These improvements resolve longstanding discrepancies between measured and predicted Belle~II background levels, and significantly reduce the computing time required to optimize the collimation system in simulation. Finally, we report on collimator aperture scans, which confirm the accuracy of the simulation and suggest a new method for aligning the collimators.