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

寻找超越标准模型的新物理是粒子物理学的前沿。对粒子自转的精确实验形成了一条通往重大发现的有希望的道路。实验正在准备寻找质子和氚的电偶极矩。这样的偶极矩将证明对CP和T对称的破坏，并将揭示宇宙中异常大的重子不对称性。类轴子粒子是宇宙中无法解释的暗物质的有趣候选者，它会引入振荡偶极矩，这可以在自旋实验中检测到。在同一类中，寻找强子相互作用中的半强CP破坏和T破坏，在百万分之几的水平上寻找T破坏效应。精密自旋实验的另一个领域是长期存在的核子自旋危机，其中迄今鲜为人知的氚张量结构函数正在进入焦点。所有上述项目都需要严格控制存储环中的自旋取向，自旋取向的灵活性和长的自旋相干时间。通过我们的SpinTra项目，我们将开发一种新的方法来控制储存环中的旋转，并将其对准任何所需的方向。该方法是由尤里·菲拉托夫及其合作者提出的。他也是该项目的俄罗斯PI。我们将制定理论基础，通过数值模拟验证概念，建立所需的硬件，将其安装在FZ Jülich的COSY环中，并通过原理验证实验论证其可行性。如果成功，该方法可用于增强美国布鲁克海文实验室的电子-离子对撞机EIC、俄罗斯的核子对撞机设施NICA、中国的电子-离子对撞机、或者用于搜索电偶极矩的半电动和全电动存储环。MIPT的俄罗斯小组与RWTH Aachen University和Forschungszentum Jülich的德国小组之间的跨国合作对这些项目的成功至关重要。MIPT小组在理论方面贡献了他们的专业知识，他们将为原则证明建立硬件。德国团队提供了COSY设备，这是一种用于此类实验的独特设备，以及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.