Excellence in Research: Constraining the symmetry energy in nuclear equation of state for neutron rich systems: A study of Isovector Giant Quadrupole Resonance by Compton Scatterin

该奖项支持了一种新的方法，即对重中子富核的激发态或共振进行有针对性的测量，以更好地了解中子星的性质和行为。这是因为推动中子穿过原子核形成厚中子皮的压力与支持中子星在引力作用下坍缩的压力是相同的。此外，在中子星的液体核心和固体外壳之间的边界上，转变密度和压力等量取决于富中子物质的性质。该奖项支持的协作环境将通过提供指导研究经验的机会，使非裔美国学生能够招募和保留STEM教育。在培训期间获得的技能将为这些学生准备高级学位和适合职业的经验，以缓解国家实验室STEM专业中代表性不足的少数民族的稀缺，并将为培养整体多样化和有竞争力的科学劳动力做出积极贡献。最近的理论研究表明，共振参数可以用来建立状态方程中对称能量项的必要约束。最大的挑战之一是将EoS的性质与核可观测物联系起来。有希望的核观测包括中子皮厚度的测量和由质子和中子集体运动引起的核激发的性质，例如，等矢量巨型四极共振（IVGQR）。IVGQR是原子核的集体模式，其特征是质子对中子的非相振荡。恢复力是由于对称能项出现在核方程中。因此，该奖项支持的IVGQR参数的系统确定将为EoS中的对称能项提供重要的约束。对于Sn-112和Sn-114同位素，支持活动将产生不确定性为1%或更好的极化不对称数据。这些数据将允许提取IVGQR能量的质量依赖关系，共振宽度，以及能量加权和规则的消耗，其不确定性大大低于任何先前的测量。这些共振参数将改进理论模型，进一步限制富中子物质状态方程中的对称能。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award supports a novel approach of making targeted measurements of the excited states or resonances of heavy neutron-rich nuclei to better understand the properties and behavior of neutron stars. This is because the pressure that pushes neutrons across the nucleus to form a thick neutron skin is the same pressure which supports a neutron star collapsing against the pull of gravity. Furthermore, at boundaries between the liquid core and solid crust of a neutron star, quantities such as the transition density and the pressure depend on the properties of the neutron rich matter. The collaborative environment supported by this award will enable recruitment and retention of African American students to STEM education by providing opportunities in mentored research experiences. The skills acquired during the training will prepare these students for advanced degrees and experience appropriate for careers to mitigate the scarcity of underrepresented minorities in national laboratory STEM professions and will contribute positively to the production of an overall diverse and competitive scientific workforce.Recent theoretical studies show that resonance parameters can be used to establish the necessary constraints on symmetry-energy terms in the Equation of State (EoS). One of the big challenges is relating properties of the EoS to nuclear observables. Promising nuclear observables include the measurement of neutron-skin thickness and properties of nuclear excitations arising from collective motion of protons and neutrons, for example, the Isovector Giant Quadrupole Resonance (IVGQR). The IVGQR is a collective mode of the nucleus characterized by the out-of-phase oscillation of protons against neutrons. The restoring force is due to the symmetry energy term which appears in the nuclear EoS. Therefore, the systematic determination of the IVGQR parameters supported by this award will provide important constraints on the symmetry energy term in the EoS. The supported activities will produce polarization asymmetry data with uncertainties of 1% or better for the Sn-112 and Sn-114 isotopes. These data will allow extraction of the mass dependencies of the IVGQR energy, the resonance width, and the depletion of the energy-weighted sum rule with uncertainties considerably lower than any previous measurement. These resonance parameters will improve theoretical models with further constraints on the symmetry energy in the equation of state for neutron rich matter.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.