暗物质、中微子质量及逆一阶电弱相变的单态-双态费米子起源
Singlet-Doublet fermion origin of dark matter, neutrino mass and inverse first-order electroweak phase transition
AI总结：
该研究基于 Scotogenic 型辐射中微子质量模型，引入单态-双态费米子等扩展标准模型，实现逆一阶电弱相变，其允许参数空间可被未来多类实验探测。
AI中文摘要：
我们在一种 Scotogenic 型辐射中微子质量模型中研究逆一阶电弱相变（IFOEWPT）及可观测引力波（GW）的可能性，该模型中，单态-双态（SD）费米子（其最轻粒子为暗物质（DM）候选体）在单圈水平产生必要的 seesaw 机制。为简化起见，考虑轻中微子为狄拉克中微子及额外探测前景，我们将标准模型（SM）扩展为包含两代 SU(2)_L 单态和双态费米子、一个单态标量及三个右手中微子（RHNs）。RHNs 提供轻狄拉克中微子的右手手征部分，而 SD 费米子与标量单态促成单圈中微子质量图。较轻 SD 费米子的中性组分在剩余 Z_2 对称性下稳定，扮演 DM 的角色；较重的 SD 费米子与希格斯强耦合，引发 IFOEWPT，使宇宙从对称希格斯相过渡到最终破缺希格斯相时经历两次不同的一阶相变。我们结合不同实验的现有约束，从产生正确中微子质量、DM 遗迹密度及 IFOEWPT 的要求出发，对参数空间进行约束。该模型最终允许的参数空间可在未来的对撞机、直接探测、GW 及宇宙微波背景（CMB）实验中进行探测。
英文摘要：
We study the possibility of an inverse first-order electroweak phase transition (IFOEWPT) and observable gravitational waves (GW) in a radiative neutrino mass model of scotogenic type where singlet-doublet (SD) fermions, the lightest of whom is the dark matter (DM) candidate, generate the necessary seesaw at one-loop level. Considering the possibility of light neutrinos being Dirac for simplicity and additional detection prospects, we extend the standard model (SM) with two generations of $SU(2)_L$ singlet and doublet fermions, one singlet scalar, and three right-handed neutrinos (RHNs). While RHNs provide the right chiral parts of light Dirac neutrinos, the SD fermions and the scalar singlet facilitate the one-loop neutrino mass diagram. The neutral component of the lighter SD fermion, stabilized under a residual $Z_2$ symmetry plays the role of DM while the heavier SD fermions strongly couple to the Higgs leading to an IFOEWPT where the Universe undergoes two different first-order phase transition as it goes from the symmetric to the final broken Higgs phase. We constrain the parameter space from the requirements of generating the correct neutrino mass, DM relic as well as IFOEWPT while incorporating the existing constraints from different experiments. The final allowed parameter space of the model can be probed at collider, direct-detection, GW and cosmic microwave background (CMB) experiments in near future.
