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

该奖项支持一种新的方法，对重富中子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，与支撑中子星星克服引力坍缩的压力相同。此外，在中子星星的液态核和固态壳之间的边界处，诸如跃迁密度和压力之类的量取决于富中子物质的性质。 该奖项支持的合作环境将通过提供指导研究经验的机会，招募和保留非裔美国学生接受STEM教育。在培训期间获得的技能将为这些学生获得高级学位和适合职业的经验做好准备，以缓解国家实验室STEM专业中少数民族代表性不足的问题，并将积极促进整体多元化和有竞争力的科学劳动力的生产。最近的理论研究表明，共振参数可以用来建立对称性的必要约束-状态方程（EoS）中的能量项。 最大的挑战之一是将EoS的属性与核可观测数据联系起来。有前途的核观测包括测量中子皮厚度和质子和中子集体运动产生的核激发特性，例如等矢量巨四极共振（IVGQR）。IVGQR是原子核的集体模式，其特征在于质子对中子的异相振荡。恢复力是由于出现在核EoS中的对称能量项。因此，由该奖项支持的IVGQR参数的系统确定将对EoS中的对称能量项提供重要的约束。 所支持的活动将产生极化不对称数据，Sn-112和Sn-114同位素的不确定性为1%或更好。这些数据将允许提取IVGQR能量的质量依赖性，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以前的测量。这些共振参数将改善理论模型，进一步限制中子丰富的物质状态方程中的对称能。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

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.