SFB 1044: The Low-Energy Frontier of the Standard Model: From Quarks and Gluons to Hadrons and Nuclei

CRC 1044研究强子的作用，强子是由夸克和胶子组成的亚原子粒子，在粒子物理学，原子物理学和核天体物理学的更广泛背景下。为了回答最高和最低能量尺度上的物理学问题，强子物理学起着中心和连接作用。在上述研究领域的几乎所有前沿问题中，进展都受到量子染色体动力学（QCD）非微扰域内强相互作用定量知识缺失的限制。一方面，推进标准模型的低能前沿对物理学的核心问题有直接影响。另一方面，原子和粒子物理学中的精确测量导致了对强子结构的新见解，以及强子如何从其组成的夸克和胶子中出现的问题。在CRC 1044中，我们能够通过美因茨微波加速器（MAMI），北京谱仪BES-III和新的美因茨能量恢复超导加速器MESA之间的战略合作来实现这些研究目标，MESA将在未来四年内开始获取数据。它的光束具有迄今为止无与伦比的强度，它将允许新的测量，从寻找轻的假设粒子，超越粒子物理学的标准模型，直到质子电荷半径的超高精度测量。 通过电子散射测量（MAMI和梅萨），电子-正电子物理学（BESIII）的独特组合，以及最先进的理论计算，CRC 1044将决定性地推进低能前沿。CRC 1044的亮点是世界范围内对电子-质子散射中弱混合角的最精确测量，以及将导致改善μ子异常磁矩知识的测量和理论计算。核子形状因子和极化率的新的测量活动，结合更精细的理论分析，允许重要地改进在μ子原子中的兰姆位移的高精度测试的解释中的限制因素，并阐明质子半径之谜。一个光子-光子物理程序，旨在提取介子跃迁形状因子，允许导出更精确的约束，对μ子的异常磁矩的光-光强子贡献。此外，光谱学的研究将允许解释最近发现的由四个夸克组成的新的奇异介子。最后，在核系统中的测量允许研究核状态方程，解决天体物理学中的重要问题，如中子星的详细结构。

The CRC 1044 studies the role of hadron¬s, which are subatomic particles built up from quarks and gluons, within the broader context of particle physics, atomic phy-sics, and nuclear astrophysics. To answer physics questions at both the highest and low¬est energy scales, hadron physics plays a central and connecting role. In nearly all questions at the forefront of the mentioned research fields, the progress is limited by a missing quantitative knowledge of the strong interaction in the non-perturbative do¬main of Quantum Chromo Dynamics (QCD). On the one hand, advancing this low-en¬ergy frontier of the Standard Model has a direct impact on central questions in physics. On the other hand, precision measurement e.g. in atomic and particle physics lead to new insights on the structure of hadrons, as well as to the question how hadrons emerge out of their constituent quarks and gluons. In CRC 1044, we are in the position to fulfill these research goals by a strategic cooperation between the Mainz Microtron (MAMI), the Beijing Spectrometer BES-III, and the new Mainz Energy Recovering Superconducting Accelerator MESA, which will start taking data within the next four years. With its beam with a hitherto unrivaled intensity, it will allow for new measurements reaching from a search for light hypothetical particles, beyond the Standard Model of particle physics, till ultra-high precision measurements of the proton charge radius. Through a unique combination of measurements in electron scattering (MAMI and MESA), in electron-positron physics (BESIII), with state-of-the-art theoretical calculations, CRC 1044 will allow to decisively advance the low-energy frontier. The highlights of CRC 1044 are the most precise measurement worldwide of the weak mix¬ing angle in electron-proton scattering, as well as measurements and theoretical cal¬culations which will lead to an improved knowledge of the anomalous magnetic mo¬ment of the muon. A new measure¬ment campaign of nucleon form factors and polarizabilities, combined with more refined theoretical analyses, allows to importantly improve on the limiting fac¬tors in the interpretation of high precision tests of the Lamb shift in muonic atoms and to shed light on the proton radius puzzle. A photon-photon physics program, aimed at extracting me¬son transition form factors, allows to derive more precise constraints on the light-by-light hadronic contribution to the anomalous magnetic moment of the muon. Further¬more, studies of spectroscopy will allow for an interpretation of recently discovered new exotic mesons, composed of four quarks. Finally, measurements in nuclear systems allow to study the nuclear equation of state, addressing important questions in astrophysics, such as the detailed structure of neutron stars.