[Moller] Improved simulation of beam backgrounds and collimation at SuperKEKB

[Jay Benesch]

This appears to be very relevant to MOLLER and the simulations now in progress.   (and if you're not on the Hall A collaboration mailing list and so didn't get the draft article on the MOLLER beam line changes, email me.)

https://arxiv.org/abs/2104.02645 

Improved simulation of beam backgrounds and collimation at SuperKEKB
A. Natochii (1), S. E. Vahsen (1), H. Nakayama (2 and 3), T. Ishibashi (2), S. Terui (2) ((1) University of Hawaii, (2) High Energy Accelerator Research Organization, (3) The Graduate University for Advanced Studies)

    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. 

Comments: 	18 pages, 30 figures (including subfigures), 5 tables, to be submitted to PRAB
Subjects: 	Accelerator Physics (physics.acc-ph); High Energy Physics - Experiment (hep-ex)
Cite as: 	arXiv:2104.02645 [physics.acc-ph]