AI 中文总结
研究通过扩展标准模型引入离散\(Z_N\)规范对称性来探讨马约拉纳暗物质，经失准机制产生暗物质，考虑不同宇宙学历史并对比多种约束，发现\(Z_5\)模型被排除，\(Z_7\)等模型可行且\(Z_7\)可被未来\(MeV\)伽马射线观测探测。
AI 中文摘要
我们在一个最小设定下研究马约拉纳暗物质，其中标准模型通过三个右手中微子和一个复标量场进行扩展。该理论由精确的离散规范对称性\(Z_N\subset U(1)_{B - L}\)定义，而全局\(U(1)_{B - L}\)对称性仅在低能时作为偶然对称性出现。对于离散对称性\(Z_N\)的非平凡选择，如\(Z_5\)、\(Z_7\)、\(Z_{11}\)和\(Z_{13}\)，普朗克抑制算符明确打破这种偶然对称性并产生小的马约拉纳质量，使产生的赝南布 - 戈德斯通玻色子成为有充分动机的暗物质候选者。我们研究了暴胀后通过失准机制产生暗物质的情况，考虑了辐射主导和早期物质主导的宇宙学历史，并将可行参数空间与等曲率界限、宇宙学约束和间接暗物质搜索进行对比。我们发现\(Z_5\)模型因主导暗物质衰变成中微子的限制而被排除，而其他模型仍然可行。特别是，\(Z_7\)情景预测马约拉纳质量在\(1 - 10\,\text{MeV}\)范围内，未来的\(MeV\)伽马射线观测，尤其是利用COSI，通过马约拉纳衰变成电子 - 正电子对的511\,\text{keV线和衰变成两个光子的单色伽马射线线，可以对其进行灵敏探测。
英文摘要
We investigate majoron dark matter in a minimal setup, where the Standard Model is extended by three right-handed neutrinos and a complex scalar field. The theory is defined by an exact discrete gauge symmetry, $Z_N\subset U(1)_{B-L}$, while the global $U(1)_{B-L}$ symmetry emerges only as an accidental symmetry at low energies. For nontrivial choices of the discrete symmetry $Z_N$, such as $Z_5$, $Z_7$, $Z_{11}$, and $Z_{13}$, Planck-suppressed operators explicitly break this accidental symmetry and generate a small majoron mass, making the resulting pseudo-Nambu--Goldstone boson a well-motivated dark matter candidate. We study its production via the misalignment mechanism after inflation, considering both radiation-dominated and early matter-dominated cosmological histories, and confront the viable parameter space with isocurvature bounds, cosmological constraints, and indirect dark matter searches. We find that the $Z_5$ model is excluded by limits on the dominant dark matter decay into neutrinos, whereas the other models remain viable. In particular, the $Z_7$ scenario predicts a majoron mass in the $1$--$10\,{\rm MeV}$ range and can be sensitively probed by future MeV gamma-ray observations, especially with COSI, through the 511$\,$keV line from the majoron decay into an electron--positron pair and the monochromatic gamma-ray line from its decay into two photons.
Comments34 pages, 7 figures
