First-Principle Nuclear Structure and Reactions for Astrophysics and Experiments with Rare Isotope Beams

核裂变这一具有历史意义的发现表明，中子和质子之间的强键断裂会释放出巨大的能量。在此之后，核物理学家们一直在寻找对原子核性质更全面的解释。这些进展对于在恒星合并和爆炸等极端条件下预测奇异核以及探测中微子相关过程至关重要。最近出现的放射性束流设备使基于原子核碰撞及其反应的外来核测量成为可能。为了预测难以接近的原子核，必须很好地理解和模拟这些反应。然而，精确的解存在于大约5个粒子。该计划的目标是通过为反应模拟提供输入，极大地扩展核反应理论的能力，这些模拟是锚定在第一原理中，但也可以适应更重的原子核和增强的变形。这对于元素起源的研究非常重要，这是当今物理学中最大的挑战之一，并且具有更广泛的影响，因为核能应用和国家安全研究也有类似的需求。未来的领导者（博士后和学生）将接受低能核科学和千万亿次计算方面的培训，同时推进一个用于研究和教育目的的网络数据库。总体目标是从放射性束流设施的实验中学习和提供信息，并预测实验上无法接近的原子核的性质，这是提高我们对天体物理过程知识的关键。该计划的重点是通过从第一性原理（历史上，被称为光势并适合实验数据）构建目标和抛射物之间的有效相互作用来改进反应模型，这些原理现在解释了参与原子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重要输入，因此新的发展可以作为广泛研究的重要工具。该项目利用了一种对称导向的方法，通过利用已知的主导动力学的对称性，可以从头开始研究更重的核物种，无论是否变形。在这种方法中，所有参与的粒子都在“壳模型”图像中以相同的基础处理，同时利用质子和中子之间的手性有效场论相互作用。最终成果包括计算增强变形核中的β衰变，以及可观测到的反应，例如散射、电荷交换和（d,p）反应的截面，这些对天体物理学很重要。该项目推进了“宇宙之窗：多信使天体物理学时代”的目标，这是美国国家科学基金会未来投资的十大理念之一。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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 objective of this program is to expand dramatically the capabilities of nuclear reaction theory, by providing input to reaction simulations that is anchored in first principles but also can accommodate heavier nuclei and enhanced deformation. This is important for studies of the origin of elements, one of the biggest challenges in physics today, and has a wider impact since nuclear energy applications and national security research have similar needs. Future leaders (postdoc and students) are trained in low-energy nuclear science and petascale computing, while advancing 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. The program focuses on improving 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), which now 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 serve as an important tool in a broad spectrum of studies. The project capitalizes 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 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.