We derive limits on millicharged dark states, as well as particles with electric or magnetic dipole moments, from the number of observed forward electron scattering events at the Big European Bubble Chamber in the 1982 CERN-WA-066 beam dump experiment. The dark states are produced by the 400~GeV proton beam primarily through the decays of mesons produced in the beam dump, and the lack of excess events places bounds extending up to GeV masses. These improve on bounds from all other experiments, in particular CHARM~II.

中文翻译：

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过去的爆炸：BEBC WA66光束倾卸实验对暗区的约束

我们根据1982年CERN-WA-066束流倾倒实验在欧洲大气泡室观察到的正向电子散射事件的数量，得出了带电暗态以及具有电或磁偶极矩的粒子的限制。暗态是由400〜GeV质子束产生的，主要是通过束流收集器中产生的介子的衰变而产生的，并且缺少多余的事件，使边界扩展到GeV质量。这些在所有其他实验（特别是CHARM_II）的界限上都有所改善。