Scaling of anisotropic flows and nuclear equation of state in intermediate energy heavy ion collisions

Elliptic flow ($v_2$) and hexadecupole flow ($v_4$) of light clusters have been studied in detail for 25 MeV/nucleon $^{86}$Kr + $^{124}$Sn at large impact parameters by using a quantum molecular dynamics model with different potential parameters. Four sets of parameters including soft or hard equation of state (EOS) with or without symmetry energy term are used. Both number-of-nucleon ($A$) scaling of the elliptic flow versus transverse momentum ($p_{\rm t}$) and the scaling of $v_4/A^{2}$ versus $(p_{\rm t}/A)^2$ have been demonstrated for the light clusters in all above calculation conditions. It is also found that the ratio of $v_4/{v_2}^2$ maintains a constant of 1/2 which is independent of $p_{\rm t}$ for all the light fragments. Comparisons among different combinations of the EOS and the symmetry potential term show that the above scaling behaviours are sound and independent of the details of potential, while the strengths of flows are sensitive to the EOS and the symmetry potential term.     

Isoscaling of projectile-like fragments

In this paper, the isotopic and isotonic distributions of projectile fragmentation products have been simulated by a modified statistical abrasion--ablation model and the isoscaling behaviour of projectile-like fragments has been discussed. The isoscaling parameters α and β have been extracted respectively, for hot fragments before evaporation and cold fragments after evaporation. It looks that the evaporation has stronger effect on α than β. For cold fragments, a monotonic increase of α and β with the increase of Z and N is observed. The relation between isoscaling parameter and the change of isospin content is discussed.     

重离子碰撞中QCD物质整体极化的实验测量

高能重离子碰撞中Λ超子和φ, K^*0矢量介子的整体极化的实验数据证实了夸克物质整体极化的新现象,引起了研究人员的广泛关注,成为高能核物理前沿新的热点研究方向.本文主要从实验测量上回顾整体极化研究,着重阐述相对论重离子对撞机(RHIC)上的螺旋径迹探测器(STAR)合作组在不同对撞能量点开展的Λ超子和φ, K^*0介子的整体极化测量结果,并拓展到含有多个奇异夸克粒子Ξ,Ω的整体极化测量和Λ沿着束流方向的局域极化研究.本文也将简单点评大型强子对撞机(LHC)能区和HADES实验低能区的测量结果,并对这些实验结果给出的物理信息进行简单描述.     

高能核物理前沿：探寻夸克-胶子等离子体

 对于我们身处的物质世界,现代物理学认为它是起源于约150 亿至200 亿年前的一次宇宙大爆炸。在宇宙的早期,物质的温度和密度都相当大,整个宇宙体系达到平衡。初始的宇宙间只有正反夸克、轻子、胶子等一些基本粒子形态的物质。     

F同位素的反应总截面测量和17F可能的质子皮结构

应用透射法对中能区F同位素与C靶的反应总截面进行了测量.发现¹⁷F的反应总截面比其邻近同位素的反应总截面稍有增强.用Glauber模型和BUU模型对F同位素进行了差异因子d的分析.¹⁷F的差异因子d比其附近同位素稍有增强.分析结果表明¹⁷F可能存在质子皮结构.     

中能重离子核反应的碎裂、集体流和其同位旋效应

本文总结了中能重离子核反应的一般特征及热核反应与衰变过程的动力学、热力学和化学（同位旋组分）效应。尤其是，综合了作者在当前中能重离子核物理研究热点，如多重碎裂，“颈”发射，集体流及其同位旋物理等这些方面的系统性工作，作了较为完整深入的介绍，最后我们还对当前中能重离子核物理的发展前景作了扼要的介绍。     

中等质量核激发态奇异核结构的研究

在球形非线性相对论平均场(RMF)的理论框架下, 研究了β稳定线附近中等质量(z=20—50)奇A核在激发态下存在的晕或皮结构, 提取了价核子与核芯均方根半径的比值(R_vc), 并结合单中子或质子的分离能(Sn(p)), 讨论了具有晕或皮结构的激发态所呈现出来的带状分布, 说明了壳层结构与离心势垒对激发态晕或皮结构形成的重要影响.     

化学非平衡夸克–胶子等离子体中的双轻子产生

研究了正在进行化学平衡的具有有限重子密度的夸克–胶子等离子体系统的演化和双轻子产生.结果发现由于夸克相的寿命随初始夸克化学势的增加而增加,以及其他一些因素,如较高的初始温度、较大的胶子密度和较大的胶子聚变和夸克湮没反应截面,导致热粲夸克对双轻子产生提供了占统治的贡献.这个效应造成中等质量双轻子的重大增强.     

同位旋标度规律的动力学和统计衰变效应

通过同位旋相关的量子分子动力学模型和统计级联衰变模型, 计算了两个相似的同位旋不同的反应系统的同位旋标度规律, 计算的结果表明对于轻粒子碎片, 同位旋标度系数α随反应时间的增加有所变大, 而对于重的余核产物, α随反应时间的增加有所减小; 轻粒子碎片的α基本上保持不变化, 中等质量和重的余核, α与产物的大小相关, 产物越重α越大. 统计级联衰变可以稍微增加同位旋标度参数α, 但是不改变α对于轻粒子和重产物的变化规律.     

A Search for Solar Axions and Anomalous Neutrino Magnetic Moment with the Complete Panda X-Ⅱ Data

We report a search for new physics signals using the low energy electron recoil events in the complete data set from PandaX-Ⅱ,in light of the recent event excess reported by XENON1 T.The data correspond to a total exposure of 100.7 ton·day with liquid xenon.With robust estimates of the dominant background spectra,we perform sensitive searches on solar axions and neutrinos with enhanced magnetic moment.It is found that the axionelectron coupling gAe<4.6×10^-12 for an axion mass less than 0.1 keV/c² and the neutrino magnetic moment μv<4.9×10^-11μB at 90%confidence level.The observed excess from XENON1 T is within our experimental constraints.