Studies of the Equation of State of Asymmetric Nuclear Matter

这项拨款建议是为了研究不对称核物质的状态方程。状态方程是核物质的基本性质，它描述了核系统的能量、压力、温度、密度和同位旋不对称性之间的关系。它可以分为与同位旋不对称性无关的对称物质贡献和与不对称性的平方成正比的同位旋项(也称为对称能)。不对称核物质的状态方程对于理解孤立中子星和双中子星、II型超新星和中子星合并的物理学也具有重要意义。这项赠款提案的研究方案与若干涉及中子星和引力波物理的天体物理学方面的高度优先的STFC方案之间存在着很强的协同作用，其中包括高级LIGO/GEO600、LISA和SKA。高能核-核碰撞中等标量集体振动、集体流和K介子产生的测量约束了密度从饱和密度到五倍饱和密度的对称物质的状态方程。然而，非对称物质的物态方程的实验约束相对较少。由我们领导的国际ASYEOS合作组织(欧洲、美国和日本)最近成立了一个研究不对称核物质的状态方程的组织。在这项赠款提案期间，该合作打算利用现有设施如GSI、GANIL、MSU和RIBF-RIKEN已有的稳定和稀有的同位素束流，以研究从亚饱和密度(0.5-1.0倍正常核物质密度)到过饱和密度(2.0倍正常核物质密度及以上)的对称能量的行为。这将为未来在FIRE、FRIB和EURISOL等新设施进行研究铺平道路。英国物理学家将在GSI领导200-800毫米伏的锡+锡反应的中子/质子流测量。

This grant proposal is to study the equation of state (EOS) of asymmetric nuclear matter. The EOS is a fundamental property of nuclear matter and describes the relationships between the energy, pressure, temperature, density and isospin asymmetry for a nuclear system. It can be divided into a symmetric matter contribution that is independent of the isospin asymmetry and an isospin term (also known as the symmetry energy) that is proportional to the square of the asymmetry. The EOS of asymmetric nuclear matter is also a quantity of crucial significance in understanding the physics of isolated and binary neutron stars, type II supernovae and neutron star mergers. Strong synergies exist between the research programme of this grant proposal and several high priority STFC programmes in astrophysics which address the physics of neutron stars and gravitational waves, including Advanced LIGO/GEO600, LISA and SKA. Measurements of isoscalar collective vibrations, collective flow and kaon production in energetic nucleus-nucleus collisions have constrained the equation of state for symmetric matter for densities ranging from saturation density to five times saturation density. However, the EOS of asymmetric matter has comparatively few experimental constraints. The international ASYEOS collaboration (Europe, the USA and Japan), of which we are leading members, has recently been formed to study the EOS of asymmetric nuclear matter. In the period of this grant proposal, the collaboration intends to exploit the stable and rare isotope beams already available from existing facilities such as GSI, GANIL, MSU and RIBF-RIKEN to study the behaviour of the symmetry energy from sub-saturation densities (0.5-1.0 times normal nuclear matter density) to supra-saturation densities (2.0 times normal nuclear matter density and above). This will pave the way for studies in the future at new facilities such as FAIR, FRIB and EURISOL. The UK physicists will lead the neutron/proton flow measurements in Sn+Sn reactions at 200-800 AMeV at GSI.