First Measurements of Beam Backgrounds at SuperKEKB
P.M. Lewis, I. Jaegle, H. Nakayama, A. Aloisio, F. Ameli, M. Barrett,, A. Beaulieu, L. Bosisio, P. Branchini, T.E. Browder, A. Budano, G. Cautero,, C. Cecchi, Y.-T. Chen, K.-N. Chu, D. Cinabro, P. Cristaudo, S. de Jong, R. de, Sangro, G. Finocchiaro, J. Flanagan, Y. Funakoshi

TL;DR
This paper reports the first measurements of beam-induced backgrounds at SuperKEKB during its initial commissioning, highlighting discrepancies between observed backgrounds and simulations, which are critical for the Belle II experiment's success.
Contribution
It provides the first experimental measurements of beam backgrounds at SuperKEKB, comparing them with simulations, and discusses implications for future collider operation and detector safety.
Findings
Measured beam backgrounds are higher than predicted by simulations.
Beam-gas and Touschek backgrounds are elevated, especially in HER.
Neutron backgrounds are higher than expected, requiring further study.
Abstract
The high design luminosity of the SuperKEKB electron-positron collider is expected to result in challenging levels of beam-induced backgrounds in the interaction region. Properly simulating and mitigating these backgrounds is critical to the success of the Belle~II experiment. We report on measurements performed with a suite of dedicated beam background detectors, collectively known as BEAST II, during the so-called Phase 1 commissioning run of SuperKEKB in 2016, which involved operation of both the high energy ring (HER) of 7 GeV electrons as well as the low energy ring (LER) of 4 GeV positrons. We describe the BEAST II detector systems, the simulation of beam backgrounds, and the measurements performed. The measurements include standard ones of dose rates versus accelerator conditions, and more novel investigations, such as bunch-by-bunch measurements of injection backgrounds and…
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