Window on the Universe: Equation of State of Asymmetric Nuclear Matter

宇宙之窗：不对称核物质的状态方程LIGO-Virgo合作对中子星(NS)合并的壮观GW170817引力波(GW)观测伴随着伽马射线、光学和无线电信号的探测。这些协同观测是美国尖端科学投资的成果。这些投资开启了同步多信使天体物理学的新时代，并提供了NS合并、千新星和伽马射线爆发之间以及NS合并和重元素核合成之间的明确联系。拟议的研究计划扩大了这些多信使研究的范围，将支持NS的富含中子物质内的力的实验限制的相关信息包括在内。它讨论了2015年核科学长程计划中有关中子星和稀密核物质性质的问题，重点讨论了依赖于中子与质子不平衡的核力的性质。密歇根州立大学和FRIB为代表不足的物理学学生赞助研究，这将有助于吸引不同群体的有才华的本科生、研究生和博士后参加这个项目。这些年轻的科学家将学习探测器的设计和建造、复杂的多参数数据分析、探测器模拟和理论建模、机器学习和贝叶斯推理分析。这项培训使他们为将来在核科学以及对技术进步和国家安全至关重要的其他关键领域的工作中发挥领导作用做好准备。GW170817引力波观测和中子星内部组成探测器(NICER)最近提供的关于中子星(NS)半径的信息都限制了NS内总压力和物质密度之间的关系。然而，这两种天文观测都不能隔离对称能量。对称能是状态方程(Eos)中的一个项，它是由物质中中子和质子数量的不平衡引起的。它对NS的稳定性起着主导作用。对称能量控制着中子和质子的相对数目，以及液态NS核和固态地壳开始处的密度和压力。对称性能量还决定着中子星内是否存在反物质或奇异物质。该小组将通过实验研究来研究对称能量，并通过改变中子和质子的相对数量以及系统的密度从1/4到两倍的正常核物质密度来分离它的作用。他们将在日本理研进行实验，使用尖端仪器和理论与实验之间的合作努力，将这些发现与多信使天文学的新结果联系起来。通过将这些对称能量的新测量与现有的对含有相同数量的中子和质子的对称物质的状态方程的实验约束相结合，他们还将获得同样具有基本意义的纯中子物质的状态方程。虽然学生培训的重点是科学和技术进步，但他们也将让青年科学家参加外联活动，使非科学家更容易接触到这门科学。他们创建了使用虚拟现实应用程序的网站，以展示核碰撞、宇宙射线探测和我们的时间投影室的工作原理。通过这样的努力，他们将努力使科学对普通公众更具吸引力和激动人心。该项目推进了未来NSF投资的十大想法之一的“宇宙之窗：多信使天体物理学时代”的目标。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Windows on the Universe: Equation of state of Asymmetric Nuclear Matter The spectacular GW170817 gravitational wave (GW) observations of a Neutron Star (NS) merger by the LIGO-Virgo collaboration were accompanied by the detection of gamma-rays, optical and radio signals. These coordinated observations were the fruit of cutting-edge scientific investments by the U.S. These investments usher in a new era of synchronous multi-messenger astrophysics, and provide definitive links between NS mergers, kilonovae and gamma-ray bursts, and between NS mergers and the nucleosynthesis of heavy elements. The proposed research plan broadens these multi-messenger studies to include relevant messages from experimental constraints on the forces within neutron-rich matter that support the NS. It addresses questions of the 2015 Long Range Plan for Nuclear Science concerning the nature of neutron stars and dilute and dense nuclear matter by focusing on properties of nuclear forces that depend on neutron-to-proton imbalance. Michigan State University and FRIB sponsor research for under-represented physics students, which will help to attract a diverse group of talented undergraduate students, graduate students and postdocs to this project. These young scientists will learn about detector design and construction, complex multi-parameter data analyses, detector simulations and theoretical modeling, machine learning and Bayesian inference analyses. This training prepares them for leadership roles in the future work force both in nuclear science but also in other key areas important for technological advancement and national security. Both the GW170817 gravitational wave observations and recent messages on Neutron Star (NS) radii from the Neutron star Interior Composition Explorer (NICER) constrain the relationship between the total pressure and the matter density within NS. Neither astronomical observation isolates the symmetry energy, however. The symmetry energy is a term in the Equation of State (EoS) that arises from the imbalance in the numbers of neutrons and protons in the matter. It plays a dominant role regarding the stability of a NS. The symmetry energy governs the relative numbers of neutrons and protons, and the density and pressure where the liquid NS core ends and solid crust begins. The symmetry energy also governs whether anti matter or strange matter exist within neutron stars. The group will study the symmetry energy via experimental studies and isolate its role by varying the relative numbers of neutrons and protons and also the density of the system from ¼ to twice normal nuclear matter density. They will perform experiments at RIKEN in Japan, using cutting edge instrumentation and a collaborative effort between theory and experiment to connect the findings to emerging results from multi-messenger astronomy. By combining these new measurements of the symmetry energy with existing experimental constraints on the EoS of symmetric matter which contains equal numbers of neutrons and protons, they will also obtain the EoS of pure neutron matter which is also of fundamental interest. While the focus of the student training is on scientific and technological advancement, they will also engage young scientists in outreach activities to make this science more accessible to non-scientists. They have created websites using virtual reality apps to illustrate nuclear collisions, the detection of cosmic rays and the working principles of our time projection chamber. By such efforts, they will endeavor to make the science more appealing and exciting to the general public.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.