We study the type-II first-order electroweak phase transition and dark matter (DM) phenomenology in both real and complex singlet extensions of SM. In the real singlet extension with a $\mathbb{Z}_2$ symmetry, we show that the parameter regions favored by the phase transition suffer from strong constraints from DM direct detection so that only a negligible fraction ($f_{X}\sim 10^{-4}-10^{-5}$) of DM composed of the real singlet scalar can survive the LUX and XENON1T constraints. In the complex singlet $S$ case, we impose a $CP$ symmetry $S\to S^{*}$ to the scalar potential. The real component of $S$ can mix with SM Higgs boson while the imaginary component becomes a DM candidate due to the protection of the $CP$ symmetry. By taking into account the current experimental constraints of invisible Higgs decays, Higgs signal strength measurements, and dark matter detections, we find that there exists a large parameter space for the type-II electroweak phase transition to occur while explaining all of the dark matter relic density. We identify a subset of parameter space that is promising for future experiments, including the di-Higgs and Higgs signal strength measurements at the HL-LHC and the dark matter direct detection in the XENONnT project.

中文翻译：

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暗物质检测约束下的弱电相变

我们研究了 SM 的真实和复杂单线态扩展中的 II 型一阶电弱相变和暗物质 (DM) 现象学。在具有 $\mathbb{Z}_2$ 对称性的真实单线态扩展中，我们表明相变偏爱的参数区域受到 DM 直接检测的强约束，因此只有一小部分 ($f_{X}\sim 10^{-4}-10^{-5}$) 由真实单线态标量组成的 DM 可以在 LUX 和 XENON1T 约束下存活。在复杂的单线态 $S$ 情况下，我们将 $CP$ 对称性 $S\to S^{*}$ 强加给标量势。$S$ 的实部可以与 SM Higgs 玻色子混合，而虚部由于 $CP$ 对称性的保护而成为 DM 候选者。通过考虑不可见希格斯衰变的当前实验约束，希格斯信号强度测量，和暗物质探测，我们发现在解释所有暗物质遗迹密度的同时，存在一个很大的参数空间来发生 II 型电弱相变。我们确定了一个有希望用于未来实验的参数空间子集，包括 HL-LHC 的 di-Higgs 和 Higgs 信号强度测量以及 XENONnT 项目中的暗物质直接检测。