利用轻核的产生研究高重子密度区域的核物质相图

Study nuclear matter phase structure at high baryon density is supposed to gain understanding of the origin and the structure of matter in the universe. With the baryon chemical potential μB and temperature T, one can draw the nuclear matter (QCD) phase diagram in the two-dimension μB-T plane. From theoretical point of view, the QCD phase diagram has a rich and complicated structure. For example, at μB=0, the phase transition from QGP to normal hadronic matter is a smooth crossover. On the other had, at the high baryon region, new phase structures, such as the quarkyonic matter, have been speculated. Searching for the existence and studying the properties of Quarkyonic Matter are a hot topic and an extremely actively developing field. The Quarkyonic Matter is a system that quark degrees of freedom dominate. Quarkyonic Matter should be understood as a transitional state between dense nuclear matter and quark matter, having both aspects of them. In experiment, the Beam-Energy-Scan (BES) of the heavy-ion collision is expected to explore the phase diagram systematically. In our plan, we will study the production of light nuclei, such as deuteron, triton and their antiparticles by using a hybrid model of ultra-relativistic Quantum Molecular Dynamics (UrQMD) plus coalescence. On the experimental side, we will use the recent results from the BES at RHIC to study the light nuclei production systematically. Physical observables, such as yields, transverse momentum distributions, collectivity and coalescence parameters of these light nuclei will be studied to extract the dynamical correlation between nucleons. And hope to shed light on the structure of nuclear matter in this region.

研究高重子密度下核物质的相结构可以使我们更好的了解宇宙物质的结构和起源。相结构可以通过重子化学势、温度的二维平面核物质(QCD)相图来描述。理论研究表明, 相图有着丰富和复杂的结构。例如在重子化学势等于0的时候会发生从QGP到强子物质的平滑过渡相变，另外在高重子密度下会存在一种新的核物质相，也就是夸克素物质。寻找夸克素物质和研究它的性质是当今核物理研究的前沿和热点话题。夸克素物质是一团由夸克自由度决定的系统，它可以理解成致密核物质和夸克物质之间的过渡状态，并且拥有这两种物质的特性。实验上可以利用重离子碰撞能量扫描（BES）来系统的研究相图的这块区域。本项目旨在利用超相对论加末态强子组合模型和RIHC的低能BES的数据来研究氘核、氚核等轻核及其反粒子的产生。通过计算模型和实验中轻核的产额、横动量分布、集体流和组合参数等物理学观测量来研究核子之间的动力学关联，研究这块区域的相结构。

研究高重子密度下核物质的相结构可以使我们更好的了解宇宙物质的结构和起源。相结构可以通过重子化学势、温度的二维平面核物质(QCD)相图来描述。理论研究表明, 相图有着丰富和复杂的结构。研究 QCD 相变结构是当前高能物理理论和实验的热点和前沿。本项目利用美国布鲁克海文国家实验室 RHIC-STAR探测器上测到的能量扫描（BES）实验数据来研究氘核、氚核等轻核及其反粒子的产生。得到了很多重要的结果，氘核的横动量谱，中心快度的产额，组合参数的能量依赖关系。发现在高重子密度区域热力学和组合模型都能很好的描述氘核的产生。最重要的发现是在高重子密度区域反核子组合参数要小于核的组合参数，这说明反核的关联体积要大于核的关系体积。另外在组合参数在20 GeV 附近达到最小值，这说明有可能在这个能量附近系统状态方程发生变化。这为以后更好的研究高重子密度区域的QCD 相结构提供了实验数据参考。