We revisit the physics of neutrino magnetic moments, focusing in particular on the case where the right-handed, or sterile, neutrinos are heavier (up to several MeV) than the left-handed Standard Model neutrinos. The discussion is centered around the idea of detecting an upscattering event mediated by a transition magnetic moment in a neutrino or dark matter experiment. Considering neutrinos from all known sources, as well as including all available data from XENON1T and Borexino, we derive the strongest up-to-date exclusion limits on the active-to-sterile neutrino transition magnetic moment. We then study complementary constraints from astrophysics and cosmology, performing, in particular, a thorough analysis of BBN. We find that these data sets scrutinize most of the relevant parameter space. Explaining the XENON1T excess with transition magnetic moments is marginally possible if conservative assumptions are adopted regarding the supernova 1987A and CMB constraints. Finally, we discuss model-building challenges that arise in scenarios that feature large magnetic moments while keeping neutrino masses well below 1 eV. We present a successful ultraviolet-complete model of this type based on TeV-scale leptoquarks, establishing links with muon magnetic moment, B physics anomalies, and collider searches at the LHC.

中文翻译：

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中微子磁矩入口：宇宙学、天体物理学和直接探测

我们重新审视中微子磁矩的物理学，特别关注右手或无菌中微子比左手标准模型中微子重（高达几个 MeV）的情况。讨论的中心是检测由中微子或暗物质实验中的跃迁磁矩介导的向上散射事件的想法。考虑到来自所有已知来源的中微子，并包括来自 XENON1T 和 Borexino 的所有可用数据，我们得出了活性到无菌中微子跃迁磁矩的最强最新排除限制。然后我们研究天体物理学和宇宙学的互补约束，特别是对 BBN 进行彻底分析。我们发现这些数据集仔细检查了大部分相关参数空间。如果采用关于超新星 1987A 和 CMB 约束的保守假设，用过渡磁矩来解释 XENON1T 过剩的可能性很小。最后，我们讨论了在具有大磁矩同时保持中微子质量远低于 1 eV 的场景中出现的模型构建挑战。我们提出了一个成功的基于 TeV 尺度轻夸克的这种类型的紫外线完整模型，建立了与介子磁矩、B 物理异常和 LHC 对撞机搜索的联系。