标题： 自相互作用不对称暗物质与一种轻质量的暗光子耦合 显示英文标题

标题： Self-interacting asymmetric dark matter coupled to a light massive dark photon

摘要： 暗物质（DM）通过一种轻粒子介导的显著自相互作用，为观测到的星系子结构提供了一个有说服力的解释；此外，DM与轻粒子的直接耦合有助于早期宇宙中的DM湮灭。 如果DM丰度是由于暗粒子-反粒子不对称性引起的，DM湮灭截面可以任意大，DM与轻粒子的耦合也可以显著。 我们考虑一种不对称DM的情况，它通过一种轻（但不一定无质量）的阿贝尔规范矢量玻色子，即暗光子相互作用。 在无质量暗光子极限下，规范不变性要求DM为多组分，由不同种类的正负暗离子组成，这些暗离子部分结合成中性暗原子。 我们认为对于轻暗光子，类似的结论仍然成立；特别是，我们确定在暗光子足够轻以介导显著DM自相互作用的大部分参数空间中，DM的多组分和原子特性仍然存在。 我们讨论了这一情景中的宇宙学事件序列，包括暗不对称性的产生、湮灭的冻结、暗重组以及赋予暗光子质量的相变。 我们估计了在考虑这种宇宙学历史的情况下，自相互作用对DM晕的影响。 我们基于大晕的观测椭率施加约束，并确定DM自散射可能影响小晕动力学的区域，从而使理论与观测更加一致。 此外，我们在各种情况下估计了暗光子的宇宙学丰度，并推导了相关的限制。 显示英文摘要

摘要： Dark matter (DM) with sizeable self-interactions mediated by a light species offers a compelling explanation of the observed galactic substructure; furthermore, the direct coupling between DM and a light particle contributes to the DM annihilation in the early universe. If the DM abundance is due to a dark particle-antiparticle asymmetry, the DM annihilation cross-section can be arbitrarily large, and the coupling of DM to the light species can be significant. We consider the case of asymmetric DM interacting via a light (but not necessarily massless) Abelian gauge vector boson, a dark photon. In the massless dark photon limit, gauge invariance mandates that DM be multicomponent, consisting of positive and negative dark ions of different species which partially bind in neutral dark atoms. We argue that a similar conclusion holds for light dark photons; in particular, we establish that the multi-component and atomic character of DM persists in much of the parameter space where the dark photon is sufficiently light to mediate sizeable DM self-interactions. We discuss the cosmological sequence of events in this scenario, including the dark asymmetry generation, the freeze-out of annihilations, the dark recombination and the phase transition which gives mass to the dark photon. We estimate the effect of self-interactions in DM haloes, taking into account this cosmological history. We place constraints based on the observed ellipticity of large haloes, and identify the regimes where DM self-scattering can affect the dynamics of smaller haloes, bringing theory in better agreement with observations. Moreover, we estimate the cosmological abundance of dark photons in various regimes, and derive pertinent bounds.