暗辐射伪装成自相互作用中微子：ν中的冒充者
Impostor Among $ν$s: Dark Radiation Masquerading as Self-Interacting Neutrinos
AI总结：
该研究提出一种模型，通过BBN后、CMB前的共振转换，使中微子自相互作用与暗辐射混淆，从而缓解宇宙观测与实验室实验之间的矛盾。
摘要：
多项宇宙观测暗示中微子存在超出标准模型的自相互作用，但此类相互作用受到地面实验的严格限制。我们通过引入一种模型，使活跃中微子在BBN后、CMB时期共振转换为自相互作用的暗辐射。这一机制利用了宇宙观测无法区分中微子与具有相同丰度和自由流性质的暗辐射的事实。我们的机制基于简单的I型锯齿框架和keV尺度标量媒介，实现了两个目标：(i) 产生强烈自相互作用的暗辐射，模仿由宇宙数据 favored 的中微子自相互作用；(ii) 减少活跃中微子能量密度，缓解宇宙中微子质量限制，并缓解与中微子振荡数据的矛盾。该模型通过抑制中微子-媒介耦合的平方质量比，自然规避实验室约束。我们显示，该场景在Planck和DESI数据联合分析下优于ΛCDM，同时与其他约束一致。该机制可通过未来实验室绝对中微子质量探测和 sterile 中微子搜索测试。
英文摘要：
Multiple cosmological observations hint at neutrino self-interactions beyond the Standard Model, yet such interactions face severe constraints from terrestrial experiments. We resolve this tension by introducing a model where active neutrinos resonantly convert to self-interacting dark radiation after BBN but before CMB epoch. This exploits the fact that cosmological observables cannot distinguish between neutrinos and dark radiation with the same abundance and free-streaming properties. Our mechanism, based on a simple type-I seesaw framework along with a keV-scale scalar mediator, achieves two objectives: (i) it produces strongly self-interacting dark radiation that imitates neutrino self-interactions favored by cosmological data, and (ii) it depletes the active neutrino energy density, relaxing cosmological neutrino mass bounds and easing the tension with neutrino oscillation data. The model naturally evades laboratory constraints through suppression of the neutrino-mediator coupling by the squared mass ratio of active and sterile neutrinos. We show that this scenario is favored over $Λ$CDM by the combined Planck and DESI data, while being consistent with all other constraints. Our mechanism is testable in future laboratory probes of absolute neutrino mass and searches for sterile neutrinos.
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