Probing Dark Sector Physics in Collider and Cosmology

这一奖项资助了圣母大学蔡宇新教授的研究活动。想象一下，有可能存在另一个与我们共存于同一时空的“隐藏”世界，但它实际上对我们是看不见的，因为隐藏世界和我们的世界之间的互动非常弱。虽然这听起来像是科幻小说，但粒子物理学和宇宙学的最新发展表明，宇宙中可能确实存在一个看不见的部分。事实上，这样一个隐蔽区域的存在将有助于解释几个长期存在的理论和观测难题。蔡教授的研究旨在利用引力波、早期宇宙学和高能粒子对撞机(如大型强子对撞机)来发现这些隐藏的世界。因此，这项研究通过促进科学进步来发现新的物理定律和自然界的新组成部分，从而促进了国家利益。这项工作还将产生几个更广泛的影响。这项工作的结果不仅将指导未来的实验和技术开发，还将涉及研究生和博士后，从而为开始这一领域研究的初级物理学家提供关键培训。蔡教授还打算就他的研究成果进行公开演讲，并帮助为高中生开发外展项目。更严格地说，蔡教授将研究随机引力波背景下的能量扰动。他还将研究早期宇宙中隐藏粒子产生的引力波信号的非高斯特征的大小。这一分析的结果将有助于识别引力波探测器，这种探测器可以观察到仅通过引力与我们相互作用的隐藏世界的能量波动。蔡教授还将研究解决希格斯等级问题的模型的宇宙学特征，例如镜像双胞胎希格斯模型和N-自然度模型。基于这些场景可以在隐藏粒子之间产生声学振荡的想法，我们可以通过它们对早期宇宙中的重力扰动所引起的变化来研究这些模型。利用LHCB实验目前和预期的未来敏感性，蔡教授还将开发新的方法来研究长寿命粒子的特征，这些粒子不仅耦合到常规物质，而且还耦合到隐藏世界中的粒子。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This award funds the research activities of Professor Yuhsin Tsai at the University of Notre Dame.Imagine the possibility that there is another "hidden" world that coexists with ours in the same space and time, but which is practically invisible to us because the interactions between the hidden world and ours are very weak. While this may sound like science fiction, recent developments in particle physics and cosmology have shown that an invisible sector of the universe might actually exist. Indeed, the existence of such a hidden sector would help explain several long-standing theoretical and observational puzzles. Professor Tsai’s research is aimed at using gravitational waves, early-time cosmology, and high-energy particle colliders (such as the Large Hadron Collider) to uncover such hidden worlds. As such, this research advances the national interest by promoting the progress of science in the discovery of new physical laws and new components of the natural world. This work will also have several broader impacts. The results of this work will not only guide future experiments and technology development, but also involve graduate students and postdocs, thereby providing critical training for junior physicists beginning research in this field. Professor Tsai also intends to give public lectures on his research results and help to develop outreach programs for high-school students.More technically, Professor Tsai will study energy perturbations in the stochastic gravitational-wave background. He will also study the size of non-Gaussian signatures of the gravitational-wave signal produced by the hidden particles in the early universe. The result of this analysis will help in the identification of the gravitational-wave detectors that can observe the energy fluctuations from the hidden world that interacts with us solely through gravity. Professor Tsai will also study the cosmological signatures of models that address the Higgs hierarchy problem, such as the Mirror Twin Higgs model and the N-Naturalness model. Based on the idea that these scenarios can produce acoustic oscillations between hidden particles, we can study these model through the changes they induce for gravity perturbations in the early universe. Exploiting the current and the expected future sensitivity of the LHCb experiment, Prof. Tsai will also develop new ways to study the signature of long-lived particles that couple not only to regular matter but also to particles in the hidden world.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.