The strong force at low energies: from exotic nuclei to fundamental symmetries

低能强力：从奇异核到基本对称

• 批准号: SAPIN-2015-00043
• 负责人: Holt, Jason
• 金额: $ 2.48万
• 依托单位: TRIUMF
• 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=614394
• 关键词: strong; force; low; energies; exotic

One of the central challenges in nuclear physics is to understand and predict the properties of stable and exotic nuclei, for which three-nucleon (3N) forces are crucial and present a current frontier. This project will uniquely apply powerful many-body methods to strongly interacting nuclear systems, systematically implementing 3N forces in many-body calculations of medium-mass and heavier neutron-rich nuclei using similarity renormalization group (SRG) methods in momentum space and in-medium for consistent calculations of valence-shell interactions and electroweak operators. Chiral effective field theory (EFT) provides a systematic basis for nuclear forces including consistent many-body forces and theoretical uncertainties. With theoretical and computational advances, I am in a key position to connect the observations made in the laboratory to the underlying strong interactions governing the properties of nuclei. Applications of this work include predictions of exotic nuclei for rare-isotope beam experiments, such as those at TRIUMF, extreme neutron-rich matter in astrophysics, and the nuclear matrix elements of neutrinoless double-beta decay that probe the nature and mass scale of the neutrino.  I plan to systematically push these studies to heavy neutron-rich isotopes, reaching nickel, tin, and beyond, exploring structural evolution and limits of existence in medium-mass and heavy nuclei and make important first predictions with 3N forces in these regions.  A major future direction of this work will be going beyond semi-magic isotopic/isotonic chains. I have begun to access fluorine and neon isotopes, systematically exploring both proton and neutron driplines above 16O and 40Ca. This will present the first attempts to understand the island of inversion and r-process regions, based on NN+3N forces.  In the past year, I have made progress in applying the many-body formalism to the calculation of effective one- and two-body operators for electroweak transitions, including neutrinoless double-beta decay. First results have been published for light double-beta-decay nuclei 48Ca, 76Ge, and 82Se, where I found that the addition of these effects changed predictions of the neutrinoless double-beta-decay nuclear matrix element by 30-70%. I will apply this formalism combined with recent advances in two-body currents from chiral EFT to microscopically calculate M1, E2, and Gamow-Teller transitions in medium- and heavy-mass nuclei as well as neutrinoless double-beta-decay in heavy systems. Finally, I have recently developed a novel ab initio method, the in-medium SRG, for open-shell nuclei. This provides the first nonperturbative approach to valence-shell Hamiltonians that is feasible in practice. Very promising first results have been obtained with NN+3N forces for the oxygen isotopes and great synergy exits to explore the topics above with this method.

核物理学的核心挑战之一是理解和预测稳定核和奇异核的性质，对这些性质来说，三核子(3N)力是至关重要的，也是当前的前沿。这个项目将独特地将强大的多体方法应用于强相互作用核系统，在中等质量和更重的中子核的多体计算中系统地实施3N力，使用动量空间和介质中的相似重整化群(SRG)方法来一致计算价-壳层相互作用和电弱算符。手征有效场论(EFT)为核力提供了一个系统的基础，包括一致的多体力和理论上的不确定性。随着理论和计算的进步，我处于一个关键的位置，可以将实验室中的观测结果与控制原子核性质的潜在强相互作用联系起来。 这项工作的应用包括对稀有同位素束实验中奇异核的预测，例如在TRIUMF上的预测，天体物理学中的极端富中子物质，以及探索中微子性质和质量尺度的无中微子双β衰变的核矩阵元素。我计划系统地推动这些研究到重中子丰富的同位素，达到镍，锡，以及更远的地方，探索中等质量和重核的结构演化和存在的极限，并在这些区域用3N力做出重要的第一次预测。这项工作的一个主要未来方向将超越半魔术同位素/等深链。我已经开始接触氟和霓虹同位素，系统地探索16O和40Ca以上的质子和中子滴线。这将是基于NN+3N力来理解反转和r过程区域的第一次尝试。在过去的一年里，我在将多体形式应用于计算电弱跃迁的有效一体和两体算符方面取得了进展，包括无中微子双β衰变。第一个结果已经发表在轻的双β衰变核48Ca、76Ge和82Se上，我发现这些效应的加入改变了对无中微子双β衰变核矩阵元素的预测30%-70%。我将把这个形式论与来自手征EFT的两体电流的最新进展结合起来，用于微观计算中等质量和重质量核中的M1、E2和Gamow-Teller跃迁，以及重系统中的无中微子双β衰变。最后，我最近开发了一种新的从头算方法，即介质中SRG，用于开壳核。这提供了第一个在实践中可行的价壳哈密顿量的非微扰方法。氧同位素的NN+3N作用力已取得了非常有希望的初步结果，用这种方法探索上述问题存在着很大的协同性。