2.76 TeV铅-铅碰撞中带电粒子的方位角分布

利用多源热模型分析了ATLAS实验组2.76 TeV 铅-铅碰撞中产生的、带电粒子在多个不同中心度事例中的方位角分布,并与n=2,4,6 和n=2 的傅里叶级数形式的方位角分布进行了比较。同时,利用由多源热模型得到的散射源在横动量空间的结构参数,计算了散射源在横动量空间的各向异性率和相对膨胀率,且与相关傅里叶系数进行了比较。在各个中心度区间,横动量空间的各向异性率和相对膨胀率都小于相应的傅里叶系数,椭圆各向异性是末态方位角分布中最主要的成分,其他成分的各向异性在各中心度区间的贡献不同且作用不可忽视。We analyze the azimuthal distributions of charged particles produced in 2.76 TeV Pb-Pb collisionsfrom ATLAS experimental group in eight different centralities by using the multi-source thermal model. Themodeling results are compared with the results from Fourier series forms with n = 2,4,6 and n = 2. Meanwhile,the anisotropy ratios and the relative expansion rates of scattering source in transverse momentum space are  calculated applying the transverse structural parameters of multi-source thermal model, and the modeling results are compared with the associated fourier coefficients. The anisotropy ratios and the relative expansion rates are less than the corresponding fourier coefficients in transverse momentum space in different center intervals. Elliptical anisotropy is main component in azimuthal distribution. Other anisotropies have different contributions in different centralities, and these contributions cannot be neglected.     

25MeV/u 40Ar+115In反应碎片和轻带电粒子的方位角关联

在２５ＭｅＶ／ｕ４０Ａｒ＋１１５Ｉｎ反应的在平面和出平面大角度关联测量中,提取了碎片和α粒子之间的方位角关联函数和方位角非对称性因子．φ＝９０时,方位角关联函数呈现为最小值,表明在集体类转动效应影响下,反应产生的轻带电粒子和碎片优先在反应平面内发射．随着关联对质量的增加,在平面关联粒子的发射相对于束流轴不对称性逐渐增大．随着关联对质量的增加,相继衰变和粒子末态相互作用对φ＝０的关联粒子对方位角关联函数值的影响逐渐降低并直至消失,同时集体转动效应增强,方位角非对称性增加．     

Evidence for azimuthal correlations in inelastic interactions of56Fe nuclei in emulsion at 2.5A GeV/c

Azimuthal correlations in angles between various types of charged secondary particles from inelastic interactions of relativistic⁵⁶Fe nuclei with the nuclei of nuclear emulsions have been investigated. It is observed that all types of charged secondaries produced are emitted asymmetrically in the azimuthal plane. The degree of azimuthal asymmetry increases with the decrease of impact parameter. We have also observed that particles belonging to different kinematical regions of the nucleus-nucleus interaction (intergroup correlation) have a tendency to be emitted to the opposite sides in the azimuthal plane.     

Azimuthal anisotropies as stringent test for nuclear transport models

Azimuthal distributions of charged particles and intermediate mass fragments emitted in Au+Au collisions at 600A MeV have been measured using the FOPI facility at GSI-Darmstadt. Data show a strong increase of the in-plane azimuthal anisotropy ratio with the charge of the detected fragment. Intermediate mass fragments are found to exhibit a strong momentum-space alignment with respect of the reaction plane. The experimental results are presented as a function of the polar centre-of-mass angle and over a broad range of impact parameters. They are compared to the predictions of the Isospin Quantum Molecular Dynamics model using three different parametrisations of the equation of state. We show that such highly accurate data provide stringent test for microscopic transport models and can potentially constrain separately the stiffness of the nuclear equation of state and the momentum dependence of the nuclear interaction.     

Azimuthal Correlations of Fragments with Light Charged Particles in Reaction of 25MeV/u 40Ar+115In

The large angle correlations for in-plane and out-of-plane have been measured for the pairs of the fragments and light charged particles (LCPs) in the reaction of 25MeV/u ⁴⁰Ar+¹¹⁵In. The azimuthal correlation functions and the azimuthal asymmetry factors were obtained. The azimuthal correlation functions of all pairs between fragments and a particles are of minimum value in φ=90°plane. It indicates that the LCPs and fragments formed in the reaction exhibit an enhanced emission in the reaction plane due to collective rotation-like effect induced by attractive mean field. The more heavier the masses of the coincident LCPs and fragments are, the more stronger the left-right asymmetries of the coincident particles with respect to the beam direction in the reaction plane are, the more preferential the particle emission to the direction opposite to the coincident reaction products is. Along with the increase of the mass of the coincident LCPs and fragments, the influences of the sequential decay and particle final state interactions on the azimuthal correlation functions of the correlated pairs in the φ=0° plane decrease and vanish at last, the collective rotation-like effect is enhanced, and the azimuthal asymmetries increase.     

Role of the Coulomb interaction in the flow and the azimuthal distribution of kaons from heavy ion reactions

Coulomb final-state interaction of positive charged kaons in heavy ion reactions and its impact on the kaon transverse flow and the kaon azimuthal distribution are investigated within the framework of QMD (quantum molecular dynamics) model. The Coulomb interaction is found to tend to draw the flow of kaons away from that of nucleons and lead to a more isotropic azimuthal distribution of kaons in the target rapidity region. The recent FOPI data have been analyzed by taking into account both the Coulomb interaction and a kaon in-medium potential of the strong interaction. Although the effect of the kaon Coulomb potential on the kaon flow and azimuthal distribution is much smaller than that of the strong potential, it is found to be visible, and therefore, should be taken into account if one wants to extract unambiguous information about the kaon strong potential in nuclear matter from the kaon flow and azimuthal distribution data.     

Flow effects in high-energy nucleus collisions with Ag(Br) in emulsion

Various flow phenomena observed by a unique emulsion method are reviewed. The experimental data of the emission of projectile and target fragments and relativistic particles in collisions of 1–160 A GeV/c ¹⁶O, ²²Ne, ²⁸Si, ³²S, ⁸⁴Kr, ¹⁹⁷Au, and ²⁰⁸Pb nuclei with ¹⁰⁸Ag (⁸⁰Br) targets are investigated. The transverse-momentum approach, the flow-angle analysis using principal vectors, the azimuthal correlation functions, the method of azimuthal correlations between charged secondaries, and the method of Fourier expansion of the azimuthal angle distributions are applied. Evidence of the directed flow of spectators has been obtained in the medium-impact nuclear interactions. In azimuthal distributions, with respect to the reaction plane, the signal of the elliptic flow of participants has been observed.     

Measurement of azimuthal asymmetries in inclusive production of hadron pairs in e(+)e(-) annihilation at Belle

The Collins effect connects transverse quark spin with a measurable azimuthal dependence in the yield of hadronic fragments around the quark's momentum vector. Using two different reconstruction methods, we find evidence of statistically significant azimuthal asymmetries for charged pion pairs in e(+)e(-) annihilation at a center-of-mass energy of 10.52 GeV, which can be attributed to a transverse polarization of the primordial quarks. The measurement was performed using a sample of 79 x 10(6) hadronic events collected with the Belle detector.     

中能原子核多重碎裂中的方位角关联

在发射源静止系碎片各向同性发射的假设条件下，考虑到碎片之间的电磁作用，研究了中能原子核多重碎裂中碎片间的方位角关联，计算结果与５００─９８０ＡＭｅＶ能区的实验数据一致．     

Observation of strong azimuthal asymmetry between slow and fast particles from high energy nuclear collisions

Evidence is presented for the strong azimuthal asymmetry between slow and fast fragments in nuclear collisions in the energy interval of 0.4 to 1 GeV per nucleon. The asymmetry gets stronger when incident energy and impact parameter decrease. The results on theA dependence of the azimuthal asymmetry are also presented.     

中能核反应中反应平面的确定

介绍并分析了中高能核反应过程中与反应平面相关的可观测量 ,以及确定核反应平面的各种方法 .这些方法包括裂变碎片方位角测量、类弹碎片测量、动量流球形张量、横向动量的方向性、方位角关联和Fourier谐波分析等 . Observables that related to the nuclear reaction plane in intermediate and relativistic energy heavy ion reactions are discussed. Reaction plane determination for intermediate and relativistic energy heavy ion reactions is presented. The methods include fission fragments measurement, projectile-like fragments measurement, kinetic flow-tensor, transverse momentum directivity, azimuthal correlation, Fourier series and etc.     

Dynamics of high energy heavy ion collisions — nuclear matter at high density and temperature

Nuclear collisions at E_LAB > 50 MeV/n are studied using the nuclear fluid dynamical and the cascade model. Evidence for the predicted compression effects has been found in recent experimental data: The preferential sidewards emission of light fragments as well as the azimuthal p-p correlations indicate the presence of collective flow phenomena. The analysis of future 4π exclusive experiments in terms of the kinetic flow tensor can yield information about the equation of state of the compressed nuclear matter. We also discuss the role of pions and strange particles as probes for the properties of nuclear matter at high excitation energy.     

A geometric model of space-time and matter

A geometric model of a spin one-half charged particle based on a modified version of Weyl's unified model of electromagnetism and gravity is presented. The model predicts a short-range force which we identify with the strong force. A nuclear mass formula similar to the Weizsäcker mass formula provides experimental verification of the geometric approach.     

感应电压叠加装置中角向传输线阻抗计算

在进行感应电压叠加装置设计时, 为了使初级脉冲形成与传输系统产生的快前沿高压脉冲均匀耦合到次级传输线, 需要建立感应腔的二维电路模型对电磁波在角向传输线中的传播过程进行分析, 并基于电路计算结果优化设计角向传输线阻抗分布规律,使次级传输线中电流能够均匀分布。由于角向传输线结构复杂, 没有精确求解阻抗值的解析公式, 介绍了一种基于电报方程和瞬态电磁场仿真求解复杂结构传输线阻抗值的方法, 采用该方法对等宽度和变化宽度两种结构角向传输线阻抗值进行了评估。研究结果表明,相比于三平板传输线阻抗计算公式, 采用微带传输线阻抗计算公式对角向传输线阻抗值进行求解结果更加精确。     

Asymmetric electron-nuclear dynamics in two-color laser fields: laser phase directional control of photofragments in H+2

Exact non-Born-Oppenheimer numerical solutions of the time-dependent Schrodinger equation for the 1D H+2 molecule in an intense, two-color (omega+2omega) laser field have been obtained. Both electron and proton kinetic energy spectra show spatial, correlated, asymmetric distributions. The calculated spectra exhibit the same unusual correlations as in experiments, in which both positively charged nuclear fragments and negatively charged photoelectrons were preferentially emitted in the same direction. The above asymmetries of photoemission of electrons seen in our quantum simulation are interpreted in the framework of a quasistatic tunneling model.     

Azimuthal anisotropy of the emission of fragments and relativistic particles in collisions between iron nuclei of momentum 2.5 GeV/<Emphasis Type="Italic">c</Emphasis> per nucleon and photoemulsion nuclei

The azimuthal anisotropy of the emission of fragments and relativistic particles in collisions between ⁵⁶Fe nuclei of momentum 2.5 GeV/c per nucleon and photoemulsion nuclei is measured. For semicentral collisions at impact-parameter values in the range 0.12 ≤ b/b_max ≤ 0.70, charged fragments and relativistic particles are predominantly emitted in the direction orthogonal to the nuclear-reaction plane. The azimuthal-asymmetry parameter P₂ for fragments whose charge numbers are Z = 1, 2 and Z ≥ 3 takes values of, respectively, ?0.192±0.057, ?0.28±0.07, and ?0.39±0.12. Evaporated b particles have an isotropic azimuthal distribution.     

Azimuthal distributions of final-state particles and fragments and transverse structure of emission source in high-energy nucleus-nucleus collisions

The azimuthal distributions of final-state particles and fragments produced in high-energy nucleus--nucleus collisions are described by a modified multisource ideal gas model which contains the expansions and movements of the emission sources. The transverse structures of the sources are given in the transverse plane by momentum components p_x and p_y,and described by parameters in the model. The results of the azimuthal distributions, calculated by the Monte Carlo method, are in good agreement with the experimental data in nucleus--nucleus collisions at high energies.     

CR-39核径迹探测器及其在核科学等研究领域中的应用

介绍了一种核径迹探测器ＣＲ－３９塑料的特性,这种探测器对逞电粒子非常灵敏,它还具有稳定、透明等特点,可记录ｐ、ａ粒子,裂变碎片和其他带电粒子,它是现有固体核径迹探测器中能量沉积密度探测阈最低的材料,介绍了ＣＲ－３９对带电粒子的响应,给出了各种带电粒子的ｖＴ对限定能量损失（ＲＥＬ）的响应曲线,利用ＣＲ－３９与转换屏的组合还可测定能量范围广的中子能谱,可作为方便的个人中子剂量计,介绍了ＣＲ－３９在研究     

Electromagnetic form factors of the nucleon

Dynamical and thermal characterizations of excited nuclear systems produced during the collisions between two heavy ions at intermediate incident energies are presented by means of a review of experimental and theoretical work performed in the last two decades. Intensity interferometry, applied to both charged particles (light particles and intermediate mass fragments) and to uncharged radiation (gamma rays and neutrons) has provided relevant information about the space-time properties of nuclear reactions. The volume, lifetime, density and relative chronology of particle emission from decaying nuclear sources have been extensively explored and have provided valuable information about the dynamics of heavy-ion collisions. Similar correlation techniques applied to coincidences between light particles and complex fragments are also presented as a tool to determine the internal excitation energy of excited primary fragments as it appears in secondary-decay phenomena.     

Out-of-plane emission of nuclear matter in Au+Au collisions between 100 and 800 AMeV

We present new experimental results concerning the azimuthal distributions of proton-likes, light and intermediate mass fragments at midrapidity for Au(100–800 A MeV) +Au collisions measured with the FOPI phase-I detector at GSI in Darmstadt. The azimuthal distributions are investigated as a function of the collision centrality, the incident energy, the fragment charge and transverse momentum. The azimuthal anisotropy is maximum for impact parameters around 7 fm. Intermediate mass fragments present a stronger out-of-plane emission signal than light fragments and a saturation is reached for Z ⩾ 4. The azimuthal anisotropy increases with the fragment transverse momentum and decreases as the incident energy increases. The azimuthal anisotropy of Z = 2 particles investigated as a function of the scaled fragment transverse momentum follows an universal curve for bombarding energies between 250–800 A MeV. A signature for a transition from in-plane to out-of-plane emission is evidenced at the lowest beam energies.