发表机构
Indian Institute of Technology Guwahati; University of Pittsburgh（印度理工学院古瓦哈提分校; 匹兹堡大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出一种狄拉克-马约拉纳交替机制的轻子生成场景，利用高温下的轻子数违反实现轻子生成，同时该机制可产生可观测引力波与可探测暗辐射。
AI 中文摘要
观测到的物质-反物质不对称可通过轻子生成机制动态产生，该机制首先生成非零轻子不对称，随后通过 sphalerons 转化为重子不对称。非零轻子不对称的产生通常需要轻子数违反（LNV），在跷跷板框架内，这会导致轻中微子具有马约拉纳性质。由于地面实验未发现 LNV 的迹象，我们提出一种新颖的轻子生成场景：LNV 发生在高温下，而零温物理与轻中微子的纯狄拉克性质一致。在这种“狄拉克-马约拉纳交替机制”的具体模型中，当具有两个单位轻子数的单重态标量场获得非零真空期望值（VEV）时，狄拉克中微子的右手手征部分在早期宇宙中会获得大的马约拉纳质量，从而促进从重 Majorana 费米子的非平衡衰变中产生轻子生成。在较低温度下，标量单重态的 VEV 恢复为零，以符合轻子数守恒。一阶 VEV 恢复相变可产生可观测的引力波，而轻狄拉克中微子可在宇宙微波背景实验中产生可探测的暗辐射。
英文摘要
The observed matter-antimatter asymmetry can be generated dynamically via leptogenesis, where a non-zero lepton asymmetry is generated first and then gets converted into baryon asymmetry via sphalerons. Creation of non-zero lepton asymmetry typically requires lepton number violation (LNV) which, within the seesaw framework, results in the Majorana nature of light neutrinos. With no signs of LNV at terrestrial experiments, we propose a novel leptogenesis scenario where LNV occurs at high temperatures while zero-temperature physics is consistent with the pure Dirac nature of neutrinos. In a concrete model of this "Dirac-Majorana flip-flop", the right chiral parts of Dirac neutrinos initially acquire a large Majorana mass in the early Universe when a singlet scalar field with two units of lepton number acquires a non-zero vacuum expectation value (VEV), thereby facilitating leptogenesis from out-of-equilibrium decay of heavy Majorana fermions. At lower temperatures, the VEV of the scalar singlet gets restored to zero to be consistent with lepton number conservation. A first-order VEV-restoring phase transition can lead to observable gravitational waves, while light Dirac neutrinos can generate detectable dark radiation at cosmic microwave background experiments.
Comments10 pages, 5 captioned figures
