Weak interactions, equations of state, and the synthesis of the elements

弱相互作用、状态方程和元素合成

• 批准号: SAPIN-2016-00027
• 负责人: CaballeroSuarez, OlgaLiliana
• 金额: $ 1.46万
• 依托单位: University of Guelph
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=616797
• 关键词: Weak; interactions; equations; state; synthesis

How much and where heavy elements like Gold are synthesized is one of the major mysteries in the Universe. How these elements are synthesized is closely linked to the life and death cycle of massive stars as well as the nuclear reactions occurring in their interior. The explosive death of a massive star, known as a Supernova, could have as an outcome a black hole with some matter accreting onto it, or a neutron star, a very compact object made mainly of neutrons. During a supernova explosion the vast majority of energy is released as neutrinos, weakly interacting particles, which can travel without perturbations and reach Earth where they can be detected. Some of these neutrinos interact with matter that has been ejected during the explosion and become part of a chain of nuclear reactions that produce new elements. It is also possible that two neutron stars encounter each other. During the merger, again huge numbers of neutrinos are emitted and new neutron-rich elements can be synthesized. There are several reactions taking place in these astrophysical scenarios, including neutrino absorption, fusion, fission, beta decay, and photon absorption. All of this occurring on hundreds of different isotopes. Neutrinos determine how many neutrons vs protons are in the ejected material. However, due to the strong gravitational field caused by the massive object, these neutrinos could be deflected or absorbed. On the other hand, the different reactions depend on the physical properties of those hundreds of isotopes, many of them not yet measured and perhaps out of experimental reach. The main goals of the proposed research program are: 1) to accurately describe the neutrino fluxes emerging from Supernovae, neutron star mergers, and black hole accretion disks taking into account the strong gravitational field that these objects generate, 2) to account for the influence that reactions such as beta decay, neutrino absorption and beta delayed neutron emission have on the synthesis of neutron-rich elements, and 3) to determine the structure and transport properties of the neutron star crust. We expect that with a better description of the neutrino fluxes we will reduce the large uncertainties in the modelling of the heavy elements abundances. We also expect to suggest measurements of the physical properties of key nuclei, which are the most relevant for the synthesis of heavy elements. This outcome will benefit the scientific community as efforts can be focus on these key targets. Finally, a better understanding of the neutron star crust will allow us to interpret the observed cooling times after x-ray explosions in accreting neutron stars, and will shed light on the synthesis of proton rich nuclei speculated to have their origin in these astrophysical sites.

像金这样的重元素在哪里合成以及合成的数量是宇宙中的主要谜团之一。这些元素的合成方式与大质量恒星的生命和死亡周期以及其内部发生的核反应密切相关。 一颗大质量星星的爆炸性死亡，即超新星，可能会产生一个黑洞，一些物质会吸积在它上面，或者是一颗中子星星星，一种非常紧凑的物体，主要由中子组成。在超新星爆炸过程中，绝大多数能量以中微子的形式释放出来，中微子是一种弱相互作用的粒子，可以在没有扰动的情况下传播，并到达地球，在那里它们可以被检测到。其中一些中微子与爆炸中喷出的物质相互作用，成为产生新元素的核反应链的一部分。两颗中子星也有可能相遇。在合并过程中，大量的中微子再次被释放出来，新的富含中子的元素可以被合成。 在这些天体物理场景中发生了几种反应，包括中微子吸收，聚变，裂变，β衰变和光子吸收。所有这些都发生在数百种不同的同位素上。中微子决定了在喷射出的物质中有多少中子和质子。然而，由于大质量物体产生的强大引力场，这些中微子可能会被偏转或吸收。另一方面，不同的反应取决于这数百种同位素的物理性质，其中许多还没有测量，也许是实验无法达到的。 拟议研究计划的主要目标是：1）准确描述超新星、中子星星合并和黑洞吸积盘产生的中微子通量，同时考虑这些物体产生的强引力场，2）考虑β衰变、中微子吸收和β缓发中子发射等反应对富中子元素合成的影响，（3）确定中子星星壳的结构和输运性质。 我们希望，更好地描述中微子通量，我们将减少大的不确定性，在重元素丰度的建模。我们还希望提出对关键核的物理性质的测量，这些核与重元素的合成最相关。这一结果将有利于科学界，因为可以集中精力实现这些关键目标。最后，更好地了解中子星星地壳将使我们能够解释所观察到的冷却时间后，在吸积中子星的X射线爆炸，并将揭示富含质子的核的合成推测有他们的起源在这些天体物理学网站。