Nuclear physics of the dynamic origin of the elements

由于新的观测和大大增强的模拟能力，核天体物理学最近发现，围绕许多元素起源的谜题可能是由于它们在恒星核生产场所的动态和剧烈起源，这是简单方法无法解决的。在过去的几年里，这样的动态场景已经被确定，以解释例如，在银河系的星系化学演化中，最缺乏金属的恒星的丰度，以及奇z元素的起源。这些场景包括快速吸积的白矮星或非常缺乏金属的大质量恒星中H和He壳层对流相互作用中的中间中子捕获过程（i过程），或大质量恒星中O和c燃烧壳层合并中的对流反应核合成。最近中子星合并引力波的发现以及对可能来自衰变不稳定物质的电磁对偶光的相关观测，已经牢固地确立了动态核合成在快速中子捕获过程（r-过程）中的作用。这些动态核生产场所的重要性提出了改进不稳定物种核数据的需要。放射性同位素的短寿命在过去严重限制了实验上可获得的核数据信息，如截面和核质量。现在，有了新的实验设施，如在TRIUMF、FRIB和欧洲的其他设施的ARIEL，可以通过有针对性的、高影响的实验取得巨大进展，这些实验提供关键的核数据，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情景。该项目将结合天体物理学和核合成模拟能力，由一位经验丰富的高级研究员负责四个项目，每个项目都侧重于不同的动态核合成环境。每个项目都将由研究生进行，他们将在项目的一半时间（三年）中进行模拟和建模工作，而另一半将致力于相应领域的核物理实验。在这些领域中，核数据一旦可用，将被应用到最新一代的天体物理模拟和观测中，以最大限度地发挥核物理实验的影响。除了取得科学成果外，该项目的另一个主要目标是将核物理影响研究的技能传授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学项目的影响，涉及放射性光束，严重依赖于这种类型的活动。

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.