Nuclear physics of the dynamic origin of the elements

由于新的观测和极大地增强的模拟能力，核天体物理学最近发现，仍然围绕着许多元素的起源的谜团很可能是由于它们在恒星核生产场所的动态和猛烈的起源，这是对简单方法的挑战。在过去的几年里，已经确定了这样的动态情景，以解释银河系银河系化学演化中最缺乏金属的恒星的丰度，以及奇数Z元素的来源。这些情景包括快速吸积的白矮星或非常贫金属的大质量恒星中氢和氦壳层对流相互作用中的中间中子俘获过程(I过程)，或者大质量恒星中燃烧O和C的壳层合并中的对流反应核合成。最近发现的来自中子星合并的引力波，以及对可能来自衰变不稳定物种的光的电磁对应的相关观测，已经牢固地确立了动态核合成在快速中子俘获过程(r过程)中的作用。这些动态核生产基地的重要性提出了改进不稳定物种核数据的必要性。放射性同位素寿命短，过去严重限制了有关核数据的实验信息，如截面和核质量。现在，有了欧洲TRIUMF的Ariel、FRIB和其他设施等新的实验设施，通过有针对性的、高冲击的实验可以取得巨大的进展，这些实验提供了关键的核数据，使天体物理模拟能够区分恒星中元素的动态起源和恒星爆炸的不同场景。这个项目将结合一位经验丰富的高级研究员的天体物理和核合成模拟能力，他将致力于四个项目，每个项目都专注于不同的动态核合成环境。每个项目都将与研究生一起实施，他们将在项目期间(三年)的一半时间用于这种模拟和建模工作，而另一半将专门用于相应领域的核物理实验。在这些领域中的每一个领域，一旦获得核数据，将被用于最新一代天体物理模拟，并与观测对峙，以最大限度地发挥核物理实验的影响。除了科学成果，该项目的另一个主要目标是将用于天体物理应用的核物理撞击研究的技能转移给新一代年轻的核物理研究人员。这种技能相对罕见，但加拿大和国际核天体物理项目涉及放射性束流的影响关键取决于这种类型的活动。

Thanks to new observations and greatly enhanced simulation capabilities, nuclear astrophysics has recently discovered that the puzzle still surrounding the origin of many elements is likely due to their dynamic and violent origin in stellar nuclear production sites that defy simple approaches. In the past few years such dynamic scenarios have been identified to explain e.g. the abundances of the most metal-poor stars, as well as the origin of odd-Z elements, in the galactic chemical evolution of the Milky Way. These scenarios include the intermediate neutron-capture process (i-process) in convective interactions of the H and He shells in rapidly accreting white dwarfs or very metal-poor massive stars, or the convective-reactive nucleosynthesis in the merger of the O- and C-burning shells in massive stars. The recent discovery of gravitational waves from neutron-star mergers and the associated observation of the electro-magnetic counterpart of the light likely from decaying unstable species has firmly established the role of dynamic nucleosynthesis for the rapid neutron-capture process (r-process). The importance of these dynamic nuclear production sites has put forth the need for improved nuclear data for unstable species. The short lifetime of radioactive isotopes has seriously limited in the past the experimentally available information on nuclear data, such as cross sections and nuclear masses. Now, with new experimental facilities such as ARIEL at TRIUMF, FRIB and other facilities in Europe huge progress can be made by targeted, high-impact experiments that provide critical nuclear data to enable astrophysics simulation to distinguish between different scenarios of the dynamic origin of the elements in stars and stellar explosions.    This project will combine the astrophysics and nucleosynthesis simulation capabilities of an experienced senior researcher who will work on four projects, each of which focusses on a different dynamic nucleosynthesis environment. Each of these projects will be carried out with graduate students who will spend one half of the period of the project (three years) on this simulation and modelling effort, while the other half will be dedicated to nuclear physics experiments in the corresponding area. In each of these areas nuclear data, as it becomes available, will be implemented into the latest generation of astrophysical simulation and confronted with observations to maximize the impact of the nuclear physics experiments. Other than the science outcome, another main goal of this project is to transfer the skill of nuclear physics impact studies for astrophysics applications to a new generation of young nuclear physics researchers. This skill is relatively rare, yet the impact of the Canadian and international nuclear astrophysics programs involving radioactive beams critically depends on this type of activity.