Nuclear Matter at High Densities - Elucidating the Properties of Hadronic Resonances in the Nuclear Medium

天文设备的最新改进最近实现了一系列辉煌的发现，并引起了人们对极端条件下核物质问题的兴趣。这些条件可以在中子星和各种灾难性的天体物理现象中实现，比如中子星合并、黑洞坍塌等。描述中等密度核物质的关键参数是对称能。它可以通过测量一系列原子核的中子皮来提取。我们的团队利用美因茨MAMI设施的高强度光子束流和密封水晶球（CB）探测器，一种高度分段的光子和粒子量热计，进行了这样的测量。2018年底，由uy主导的对各种同位素（包括48Ca的旗舰测量）的“皮肤”测量计划将获得，2019年可能会有更多的光束时间。由于CB探测器的良好性能和广泛的接受度，人们基本上可以测量与主要“皮肤”测量平行的所有核目标上的光诱导反应。这为另一个引人注目的项目提供了途径——阐明核介质中强子共振的性质。特别重要的是限制最近发现的d*(2380)六夸克的相互作用。最近由uy领导的论文表明，这种新粒子设定了可实现的中子星质量的极限，在中子星合并事件（包括由此产生的引力波发射）的动力学中起着关键作用，并且可能是核物质中核到夸克-胶子等离子体跃迁的重要中间步骤。为了推进这些令人兴奋的研究，首次在介质中约束thed*(2380)的基本性质是至关重要的。我们提出了一种利用核上的非相干2(pi)0生成来寻找中位d*(2380)生成的新方法。最简单的反应是yC12—> d*+ 10N—> pi0 pi0 C12*与C12*—> C12 +y（4.4 MeV）反应。对来自激发核的额外光子的需求确保了介质中d*(2380)的产生，滤除了主要背景，并允许通过比较各种核激发态种群的强度来确定介质中的电磁特性。

Latest improvements in astronomical equipment had recently realized in a series of brilliant discoveries and riseinterest to a question of nuclear matter at extreme conditions. These conditions can be achieved in neutron stars and atvarious catastrophic astrophysical phenomena, like neutron star mergers, black hole collapses etc... The keyparameter which describes nuclear matter at moderate densities is the symmetry energy. It can be extracted bymeasurement of the neutron skins of a range of nuclei. Our group leads such measurements utilizing the high intensityphoton beam of Mainz MAMI facility with hermetic Crystal Ball (CB) detector, a highly segmented photon andparticle calorimeter. A UoY led programme of "skin" measurements on various isotopes (including the flagshipmeasurement of 48Ca) will be obtained in late 2018 with further beamtime possible in 2019. Due to the niceperformance and large acceptance of the CB detector, one can measure essentially all photo-induced reactions onnuclear targets in parallel to the main "skin" measurements. This gives access to another high profile programme -elucidating the properties of hadronic resonances in the nuclear medium. Of particular importance is constraining theinteraction of the recently discovered d*(2380) hexaquark. Recent UoY led papers indicate this new particle sets alimit on achievable neutron star masses, plays a key role in the dynamics of neutron star merger events (includingresultant gravitational wave emission) and may act as an important intermediate step in nuclear to quark-gluon plasmatransition in nuclear matter. To advance these exciting studies it is crucial to constrain the basic properties of thed*(2380) in-medium for the first time.We propose a new method to look for in-medium d*(2380) production using incoherent 2(pi)0 production onnuclei. The simplest example of such reaction would be yC12 --> d*+ 10N --> pi0 pi0 C12* with C12* --> C12 +y(4.4 MeV) reaction. The requirement for an extra photon from excited nuclei ensures in-medium d*(2380)production, filters out major backgrounds and allows to determine in-medium electromagnetic properties bycomparing the intensity of various nuclear excited state population.