In this work, we revise and update model-independent constraints from Big Bang Nucleosynthesis on MeV-scale particles ϕ which decay into photons and/or electron-positron pairs. We use the latest determinations of primordial abundances and extend the analysis in[1] by including all spin-statistical factors as well as inverse decays, significantly strengthening the resulting bounds in particular for small masses. For a very suppressed initial abundance of ϕ, these effects become ever more important and we find that even a pure `freeze-in' abundance can be significantly constrained. In parallel to this article, we release the public code ACROPOLIS which numerically solves the reaction network necessary to evaluate the effect of photodisintegration on the final light element abundances. As an interesting application, we re-evaluate a possible solution of the lithium problem due to the photodisintegration of beryllium and find that e.g. an ALP produced via freeze-in can lead to a viablesolution.

在这项工作中，我们修改和更新了大爆炸核合成对衰变成光子和/或电子-正电子对的 MeV 级粒子 φ 的与模型无关的约束。我们使用原始丰度的最新测定结果，并通过包括所有自旋统计因子以及逆衰减来扩展 [1] 中的分析，从而显着加强了结果界限，特别是对于小质量。对于非常抑制的初始丰度 φ，这些影响变得越来越重要，我们发现即使是纯粹的“冻结”丰度也会受到显着限制。在本文的同时，我们发布了公共代码 ACROPOLIS，它在数值上解决了评估光分解对最终轻元素丰度影响所必需的反应网络。作为一个有趣的应用，