Ab Initio Nuclear Structure and Reactions for Astrophysics and Neutrino Physics

在核裂变的历史性发现之后，核物理学家们一直在寻求对原子核性质的更全面的解释。核裂变体现了通过打破中子和质子之间的强键而释放的巨大能量。这些进展对于预测恒星合并和爆炸等极端条件下的奇异核过程以及探测与中微子有关的过程至关重要。最近放射性束流设备的出现使基于原子核碰撞及其反应的奇异原子核测量成为可能。要预测不可及的原子核，必须很好地理解和模拟这些反应。然而，精确的解最多存在于五个粒子左右。该项目的目标是通过为以第一原理为基础的反应模拟提供输入，从而极大地扩展核反应理论的能力，但也可以适应更重的原子核和增强的变形。后者可以帮助研究元素的起源和中微子的性质，这是当今核物理中最大的两个挑战。该项目将产生更广泛的影响，因为核能和国家安全研究有着相似的需求。未来的领导者(博士后和学生)将接受低能核科学和千万亿级计算方面的培训，同时准备一个用于研究和教育目的的网络数据库。主要目标是从放射性束流设施的实验中学习并提供信息，并预测实验中无法接触到的原子核的性质，这些性质是增进我们对天体物理过程和中微子物理的知识的关键。该计划的目标是改进反应建模，根据第一原理(历史上称为光学势，并与实验数据相适应)构建目标与射弹之间的有效相互作用，从而解释参与核的具有挑战性的微观结构。由于这些相互作用是目前使用的许多反应模型的基本输入，新的发展将成为广泛研究的重要工具。该项目将利用对称性指导的方法，通过利用已知的主导动力学的对称性，使从头开始研究较重的核物种，无论是否变形。在这种方法中，所有参与的粒子在“壳模型”图中被同等地处理，同时使用质子和中子之间的手征有效场论相互作用。最终产品将包括对加强形变的原子核中的β衰变的计算，以及对天体物理具有重要意义的反应观测数据的计算，例如散射、电荷交换和(d，p)反应的截面。该项目推进了未来NSF投资的十大想法之一的“宇宙之窗：多信使天体物理时代”的目标。该奖项反映了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。

Following the history-making discovery of nuclear fission, which manifested the huge amount of energy that is released by breaking the strong bonds between neutrons and protons, nuclear physicists have searched for ever more comprehensive explanations of the properties of the atomic nucleus. Such advances are critical to predict exotic nuclei in processes under extreme conditions as stellar mergers and explosions, and to probe neutrino-related processes. The recent advent of radioactive beam facilities has enabled exotic-nuclei measurements, based on collisions of nuclei and their reactions. To predict inaccessible nuclei, these reactions must be well understood and modeled. However, exact solutions exist up to about five particles. The goal of this project is to expand dramatically the capabilities of nuclear reaction theory, by providing input to reaction simulations that are grounded in first principles, but can also accommodate heavier nuclei and enhanced deformation. The latter can help study the origin of elements and neutrino properties, two of the biggest challenges in nuclear physics today. The project will have a wider impact because nuclear energy and national security research has similar needs. Future leaders (postdocs and students) will be trained in low-energy nuclear science and petascale computing, while preparing a web-database for research and educational purposes.The overarching goal is to learn from and inform experiments at radioactive beam facilities, and to predict properties of experimentally inaccessible nuclei that are key to advancing our knowledge about astrophysical processes and neutrino physics. The program targets to improve reaction modeling, by constructing the effective interaction between a target and a projectile from first principles (historically, referred to as an optical potential and fitted to experimental data), and thus to account for the challenging microscopic structure of the participating nuclei. As these interactions are an essential input to numerous reaction models that are currently in use, the new developments will serve as an important tool in a broad spectrum of studies. The project will capitalize on a symmetry-guided approach that, by exploiting symmetries known to dominate the dynamics, has enabled ab initio investigations of heavier nuclear species, deformed or not. In this approach, all participating particles are treated on the same footing within a "shell model" picture, while employing chiral effective field theory interactions between protons and neutrons. The end products will include calculations of beta decays in nuclei of enhanced deformation, and of reaction observables, e.g., cross sections for scattering, charge-exchange, and (d,p) reactions, of importance to astrophysics.This project advances the objectives of "Windows on the Universe: the Era of Multi-Messenger Astrophysics", one of the 10 Big Ideas for Future NSF Investments.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.