中性自然性模型的对撞机和宇宙学检验

目前大型强子对撞机（LHC）并没有发现各种期待已久的粒子，例如顶夸克伴子，人们开始建议超对称或复合希格斯中存在色中性（或标准模型中性）的顶夸克伴子，以解释LHC实验的零结果，这一类模型被统称为中性自然性模型。这一模型中顶夸克伴子携带隐藏规范群荷，这提供了独特的对撞机和宇宙学信号。申请人计划研究这一类模型中希格斯的性质，希格斯势能形状及其测量，中性顶夸克伴子的的暗簇射信号和位移顶点测量，预测100TeV对撞机上发现这一模型的能力，为CEPC和SppC提供新的科学目标。同时，目前中性自然性模型的研究中并没有提供物质反物质不对称性和中微子质量来源，因此申请人计划对这一类模型进行扩展，以容纳隐藏部分的CP破坏和重子或轻子生成。最后，申请人计划研究隐藏规范群下的暗物质和暗辐射粒子，暗物质-暗辐射间相互作用，及其对宇宙演化的影响，这拓宽了暗物质寻找的思路，并可以在下一代CMB实验上进行检验。

The large hadron collider (LHC) has not yet found any new physics so far. This raises a new problem in naturalness models: missing top partner problem, in which the top partner is crucial ingredient in supersymmetry and composite Higgs models. A new scenario proposed in 2015, the so-called neutral naturalness, starts to attract attentions. It suggests that the top partner is not charged under the quantum chromodynamics (QCD) or the standard model (SM) gauge group, and thus the neutral top partner could escape from current LHC searches. On the other hand, the top partner carries charge under hidden QCD or hidden gauge group, which brings unique collider and cosmological signatures. We propose to study proporties of the Higgs boson, shape of the Higgs potential, smoking-gun signatures of the neutral top partner, the dark shower and the displaced vertices signature at future colliders. These provide novel signatures and new directions for future CEPC and SppC colliders. Furthermore, current models of neutral naturalness have not yet accommodated origin of matter-antimatter asymmetry and origin of the neutrino mass. We plan to extend current models to includes baryogenesis or leptogenesis, and CP violation in hidden sector. Finally, we propose to study various dark matter candidates, and possible dark radiation, interactions between dark matter and dark radiation, and its impact on cosmological evolution at early universe. This new scenario on dark matter-dark radiation could shed light on dark matter searches, which could be testified at future CMB experiment.