The SuperKEKB asymmetric electron-positron collider is the upgrade of the KEKB machine and it is expected to achieve the instantaneous luminosity of 8 × 1035 cm−2s−1, 40 times higher than the record of KEKB.With the increased luminosity, the beam background is expected to grow significantly with respect to KEKB, leading, among other effects, to possible radiation damage of detector components and to performance deterioration of the Belle II detector. SuperKEKB started operating in 2018, with a stepwise reduction of the beam size at the interaction point that has been done in the last two years, studying the evolution of background conditions. We present the studies performed in 2019 to evaluate the contributions of single beam and luminosity background sources, the conditions in which the Belle II detector has been operated so far and the prospects for future operation.

中文翻译：

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SuperKEKB 和 Belle II 的光束背景评估

SuperKEKB非对称正负电子对撞机是KEKB机的升级版，有望实现8×1035 cm−2s−1的瞬时光度，比KEKB的记录高40倍。随着光度的增加，光束背景预计相对于 KEKB 会显着增长，这会导致探测器组件的可能辐射损坏和 Belle II 探测器的性能恶化等影响。SuperKEKB 于 2018 年开始运行，在过去两年中逐步减小相互作用点的光束尺寸，研究背景条件的演变。我们介绍了 2019 年进行的研究，以评估单光束和光度背景源的贡献，