Spin transparency as a new approach to precision tests of fundamental symmetries in polarization experiments at colliders and storage rings: theory and experiment

寻找标准模型之外的新物理是粒子物理学的前沿。对粒子自旋的精确实验为重大发现提供了一条有希望的途径。寻找质子和氘的电偶极矩的实验正在准备中。这样的偶极矩将证明CP和T对称性的破坏，并将揭示宇宙中巨大的重子不对称性。类轴子粒子是宇宙中无法解释的暗物质的一个有趣的候选者，它会引入振荡的偶极矩，这可以在自旋实验中检测到。在同一类别中，是在强子相互作用中寻找半强CP-和T-破坏，其中人们寻找百万分之一水平的T-破坏效应。精确自旋实验的另一个领域是长期存在的核子自旋危机，迄今为止人们对氘核的张量结构函数知之甚少。所有上述项目都需要严格控制储存环中的自旋取向，自旋取向的灵活性，以及长的自旋相干时间。通过我们的SpinTra项目，我们将开发一种新的方法来控制存储环中的自旋，并将其对准任何所需的方向。该方法由Yury Filatov及其合作者提出。他也是该项目的俄罗斯PI。我们将建立理论基础，通过数值模拟验证概念，构建所需的硬件，将其安装在FZ Jülich的COSY环中，并通过原理验证实验证明其可行性。如果成功，该方法可以应用于增强美国布鲁克海文实验室的电子-离子对撞机eIC，俄罗斯基于Nuclotron的离子对撞机fAcility NICA，中国的电子-离子对撞机（EicC），或用于寻找电偶极矩的半电和全电储存环。MIPT的俄罗斯小组与RWTH亚琛大学和Forschungszentrum Jülich的德国小组之间的跨国合作对项目的成功至关重要。MIPT小组贡献了他们在理论方面的专业知识，他们将为原理证明构建硬件。这两个德国小组提供了COSY设施，这是进行这种实验的独特设施，并提供了他们在进行高精度自旋实验方面的经验。

The search for new physics beyond the Standard Model is at the forefront of particle physics. Precision experiments on the spin of particles form a promising path to a major discovery. Experiments are in preparation to search for electric dipole moments of protons and deuterons. Such a dipole moment would demonstrate the violation of the CP- and T-symmetries and would shed light on the anomalously large baryon asymmetry of the universe. Axion-like particles, an interesting candidate for the unexplained dark matter in the universe, would introduce oscillating dipole moments, which could be detected in spin experiments. In the same category is the search for the semi-strong CP- and T-violation in hadronic interactions, where one looks for T-violating effects at the part-per-million level. Another domain of precision spin experiments is the long-standing spin-crisis of the nucleons, where the hitherto poorly known tensor structure function of deuterons is moving into focus.All aforementioned projects require stringent control of the spin orientation in storage rings, flexibility in the orientation of the spins, and long spin coherence times. With our project SpinTra we will develop a new method to control the spin in a storage ring and to align it in any desired direction. This method was proposed by Yury Filatov and collaborators. He is also the Russian PI of the project. We will work out the theoretical foundations, verify the concept with numerical simulations, built the required hardware, install it in the COSY ring at FZ Jülich, and demonstrate the feasibility with a proof-of-principle experiment.If successful, the method can be applied to enhance the science potential of the electron-Ion Collider eIC at the Brookhaven Laboratory in the US, Nuclotron-based Ion Collider fAcility NICA in Russia, the Electron-ion collider in China (EicC), or the semi-electric and all-electric storage rings for the search for electric dipole moments.The transnational collaboration between the Russian groups at MIPT and the German groups at RWTH Aachen University and the Forschungszentrum Jülich is essential for the success of the projects. The MIPT groups contribute their expertise on the theory aspects and they will built the hardware for the proof-of-principal. The German groups provide the COSY facility, a unique facility for such an experiment, and their experience in the conduction of high-precision spin experiments.