Identified particle production, azimuthal anisotropy, and interferometry measurements in Au plus Au collisions at root s(NN)=9.2 GeV

We present the first measurements of identified hadron production, azimuthal anisotropy, and pion interferometry from Au + Au collisions below the nominal injection energy at the BNL Relativistic Heavy-Ion Collider (RHIC) facility. The data were collected using the large acceptance solenoidal tracker at RHIC (STAR) detector at root s(NN) = 9.2 GeV from a test run of the collider in the year 2008. Midrapidity results on multiplicity density dN/dy in rapidity y, average transverse momentum < p(T)>, particle ratios, elliptic flow, and Hanbury-Brown-Twiss (HBT) radii are consistent with the corresponding results at similar root s(NN) from fixed-target experiments. Directed flow measurements are presented for both midrapidity and forward-rapidity regions. Furthermore the collision centrality dependence of identified particle dN/dy, < p(T)>, and particle ratios are discussed. These results also demonstrate that the capabilities of the STAR detector, although optimized for root s(NN) = 200 GeV, are suitable for the proposed QCD critical-point search and exploration of the QCD phase diagram at RHIC.

Observation of an Antimatter Hypernucleus

Nuclear collisions recreate conditions in the universe microseconds after the Big Bang. Only a very small fraction of the emitted fragments are light nuclei, but these states are of fundamental interest. We report the observation of antihypertritons-comprising an antiproton, an antineutron, and an antilambda hyperon-produced by colliding gold nuclei at high energy. Our analysis yields 70 +/- 17 antihypertritons (3/Lambda(H) over bar) and 157 +/- 30 hypertritons (H-3(Lambda)). The measured yields of H-3(Lambda) (3/Lambda(H) over bar) and He-3 ((3)(He) over bar) are similar, suggesting an equilibrium in coordinate and momentum space populations of up, down, and strange quarks and antiquarks, unlike the pattern observed at lower collision energies. The production and properties of antinuclei, and of nuclei containing strange quarks, have implications spanning nuclear and particle physics, astrophysics, and cosmology.

Longitudinal scaling property of the charge balance function in Au plus Au collisions at root s(NN)=200 GeV

We present measurements of the charge balance function, from the charged particles, for diverse pseudorapidity and transverse momentum ranges in Au + Au collisions at root S-NN = 200 GeV using the STAR detector at RHIC. We observe that the balance function is boost-invariant within the pseudorapidity coverage vertical bar-1.3, 1.3 vertical bar. The balance function properly scaled by the width of the observed pseudorapidity window does not depend on the position or size of the pseudorapidity window. This scaling property also holds for particles in different transverse momentum ranges. In addition, we find that the width of the balance function decreases monotonically with increasing transverse momentum for all centrality classes. (c) 2010 Elsevier B.V. All rights reserved.

Center of mass energy and system-size dependence of photon production at forward rapidity at RHIC

We present the multiplicity and pseudorapidity distributions of photons produced in Au + Au and Cu + Cu collisions at root(NN)-N-s = 62.4 and 200 GeV. The photons are measured in the region -3.7 < eta < -2.3 using the photon Multiplicity detector in the STAR experiment at RHIC. The number of photons produced per average number of participating nucleon pairs increases with the beam energy and is independent of (lie collision centrality. For collisions with similar average numbers of participating nucleons the photon multiplicities are observed to be similar for An + Au and Cu + Cu collisions at a given beam energy. The ratios of the number of charged particles to photons in the measured pseudorapidity range are found to be 1.4 +/- 0.1 and 1.2 +/- 0.1 for root(NN)-N-s = 62.4 and 200 GeV, respectively. The energy dependence of this ratio could reflect varying contributions from baryons to charged particles, while mesons are the dominant contributors to photon production in the given kinematic region. The photon pseudorapidity distributions normalized by average number of participating nucleon pairs, when plotted as a function of eta-Y-beam, are found to follow a longitudinal scaling independent of centrality and colliding ion species at both beam energies. (C) 2009 Elsevier B.V. All rights reserved.

Bi同位素链上原子核α衰变性质的理论研究；Theoretical Study on α Decay Properties for Bi Isotopes

采用结团模型(clustermodel)计算了从10752Te到292116共443个核素α衰变的半衰期,所得结果与实验值符合得很好,显示了结团模型可以成功地应用于研究原子核α衰变的性质。同时研究了Bi同位素链上奇A核α衰变的半衰期,计算结果与已有的实验值的偏差一般在3倍以内,进而对实验上未知α衰变半衰期的原子核的性质进行了预言。这有助于将来在实验室探测与鉴别这些原子核以及研究它们的α衰变性质。理论与实验的比较将加深人们对原子核结构的认识。

~(12)C与~(209)Bi反应中Au同位素的产额与Q_(gg)的关系；Q_(gg)-Yield Dependence of Au Isotopes in Interaction of 47 MeV/u ~(12)C With ~(209)Bi

用47MeV/u12C离子轰击天然铋靶,通过炮弹和靶核之间的核子转移反应产生Au同位素。使用放射化学方法从大量Bi和复杂反应产物中分离、纯化Au,并制备Au的γ射线测量源。使用HPGe探测器测量放射性Au同位素的γ活性。根据照射结束时Au同位素的活度和其他相关数据,确定每个Au同位素的产生截面。分析发现,缺中子Au同位素的产生截面与Qgg值之间不遵从指数依赖关系,这可用重离子碰撞中的次级过程加以解释。

塑料闪烁体β射线望远镜研制及重离子核反应类弹产物动量分布宽度的计算

本人建立了一台塑料闪烁体β射线望远镜，该望远镜由工作在符合状态的ΔE探测器和E探测器构成。ΔE探测器由ST-401型塑料闪烁体薄片（Φ 25 * 0.5）构成，用来甄别掉γ射线。E探测器由ST-401型塑料闪烁体（Φ 70 * 70，异形）构成，在跟ΔE探测器符合的条件下，用来测量β谱。光电倍增管均采用GDB-50L型。用该望远镜测量了~(207)Bi 991KeV内转换电子谱，在没有扣除电子到达E探测器闪烁体前Ni窗、E闪烁体和空气对峰的展宽的条件下，主峰分辨为38%。作为对β连续谱测量和处理方法的检验，测量了~(90)Sr-~(90)Y源的β连续谱，并且对该谱用迭代的“展开法”进行了处理。另一方面，本文还利用费米球模型，对重离子核反应类弹产物动量分布宽度进行了计算

47MeV/u~(12) C轰击~(197)Au和~(209)Bi引起的裂变关联测量

本论文的工作：利用两体裂变角关联技术，辅之以飞行时间测量，测定了47MeV/u的~(12)C轰击~(197)Au和~(209)Bi靶中心碰撞对应的线性动量转移（LMT），得到了关联裂片出射的共面歧离分布，同时还发现了关联角很小且共面歧离很大的裂变事件，并得到了其相对速度分布。从测到的LMT分布中，得到中心碰撞对应的最可几线性动量转移约占入射动量的65％，相应于单核子线性动量转移约为192MeV/c.A，进而还估算出了所形成热核的激发能上限。在对关联裂片出射的共面歧离效应研究中，发现了共面歧离宽度是热核激发能的较好量度之一。并给出了共面歧离宽度跟热核单核子激发能的经验关系；还用简化的裂片级联蒸发模型估算了蒸发中子、质子和α粒子的平均多重性

25MeV/u~(40)Ar~(15+)+~(209)Bi反应的裂变研究

本文首先回顾了重离子物理学的发展简史，并介绍了当前的一些关于重离子反应的理论方法，同时对于现在核物理的研究热点，热核的特性进行了概括性的叙述．由于裂变是作者工作的重点，因此在文章中，对裂变反应的理论也进行了介绍．为了能够清楚全面的说明我们的工作，本文对于实验装置和探测器也给出了详细的描述．最后，文章对25 MeVu Ar+Bi反应中的裂变进行了讨论．在这些讨论中，我们分析了反应中与裂变相关的数据，得到了碎片的质量，动能分布。同时运用与碎片相关联的4He粒子能谱提取了核温度和裂前裂后的4He粒子多重性，并利用这一数据计算了不同初始激发能下的裂点激发能和裂变时标.

SR型野外人工模拟降雨装置

SR型人工降雨装置是一种多喷头、多单元组合式的间歇降雨装置。选用目前国内外较理想的喷头 ,在喷头处辅以可改变喷头降水方式的机械传动装置 ,以间歇方式降雨来满足其降雨强度 ,雨滴直径大小及其分布与自然降雨相似。每个单元的有效降雨面积为 2 m× 5 m;如果 4个单元组合成 ,其长度可增加 4倍 ,有效降雨面积即 2 m× 2 0 m。装置采用轻型铝合金材料制成 ,结构简单 ,易于安装拆卸 ,适用于野外工作。

污染土壤中Sn、Hg、Sb、Bi解吸动力学特性的研究

土壤中重金属的解吸直接影响重金属在环境中的形态转化和植物有效性。文章以我国东北地区草甸棕壤作为研究对象,通过对Sn、Hg、Sb、Bi单一及复合污染土壤中Sn、Hg、Sb、Bi的解吸动力学行为的研究,探索污染土壤中重金属Sn、Hg、Sb、Bi的解吸特性与规律。结果表明,不同污染类型的污染土壤中Sn、Hg、Sb、Bi这几种重金属的解吸量随着振荡时间的延长而不断增加。重金属Sn、Hg、Sb、Bi的解吸过程可分为快速反应阶段和慢速反应阶段。描述土壤Sn、Hg、Sb、Bi解吸动力学过程的最优模型为Elovich方程,其次为双常数方程,而一级动力学方程拟合效果不佳。此外,污染土壤中重金属Sn、Hg、Sb、Bi的解吸过程受共存重金属元素的影响。