Cosmological Constraints on MeV-scale Dark Sectors

在这项工作中，我们提出了新的和完善的宇宙学约束MeV级暗部门和各种动机良好的粒子物理模型。与标准模型等离子体热耦合的新的轻态可以改变宇宙的膨胀历史，并影响原始元素的合成。我们提出了精确和强大的约束，从大爆炸核合成（BBN）和宇宙微波背景（CMB）。我们发现，BBN观测单独设置的热暗物质质量的下限为0.4兆电子伏在2西格玛的意义。还考虑了未来CMB实验的范围。在一个更地球的注意，我们重新解释的直接检测实验的结果依赖于核反冲。这样的实验失去了对亚GeV暗物质的敏感性，尽管如果有一个额外的，具有更高动量的粒子的次主导源，这是可以恢复的。我们调查的可能性，介子衰变的非弹性宇宙射线碰撞在大气中可以作为这样一个源。由此产生的约束，然后提出和映射到一个具体的粒子物理模型。最后，我们看看一个动机良好的模型，连接中微子质量和标量暗物质。使用IceCube中微子望远镜的测量值对模型中的参数进行了限制，并预测了未来的灵敏度。

In this work we present new and refined cosmological constraints on MeV-scale dark sectors and various well-motivated particle physics models. New light states thermally coupled to the Standard Model plasma can alter the expansion history of the Universe and impact the synthesis of the primordial elements. We present precise and robust constraints from Big Bang Nucleosynthesis (BBN) and the Cosmic Microwave Background (CMB). We find that BBN observations alone set a lower bound on the thermal dark matter mass to be 0.4 MeV at 2 sigma significance. The reach of future CMB experiments is also considered. On a more terrestrial note, we reinterpret the results of direct detection experiments which rely on nuclear recoils. Such experiments lose sensitivity for sub-GeV dark matter although this is recovered if there is an additional, sub-dominant source of particles with higher momenta. We investigate the possibility that decays of mesons from inelastic cosmic ray collisions in the atmosphere could act as such a source. The resulting constraints are then presented and mapped onto a concrete particle physics model. Finally, we look at a well-motivated model that links neutrino masses and scalar dark matter. Bounds on parameters within the model are placed using measurements from the IceCube neutrino telescope and future sensitivity is forecast.