Search for disoriented chiral condensate in 158<Emphasis Type="Italic">A</Emphasis> GeV Pb+Pb collisions in WA98 experiment

The current status of the search for localized domains of disoriented chiral condensates (DCC) in Pb+Pb collisions at 158A GeV/c are presented. A new method based on the discrete wavelet transformation (DWT) technique along with an analysis of correlation between charged and neutral particles has been used for the search of localized DCC domains. We show that both the methods indicate the presence of non-statistical fluctuations in data.     

400GeV/c pp碰撞产生粒子的方位角结构

利用不同的方法对400GeV/c pp碰撞多重产生的方位角结构进行了研究.一维和二维标度阶乘矩的分析结果表明两维时的间歇效应较强,这与“喷注形”多粒子产生机制是不矛盾的. 但由其它方法分析结果表明方位角结构似乎具有随机的性质,没有“喷注形”多重产生机制的证据.     

The Azimuthal Structure of Particles Produced in pp Collisions at 400 GeV/c

The azimuthal Structure of partivles produced in pp collisions at 400 GeV/c was investigated by using different methods.The analytic results of one and two-dimensional scaled factorial moments indicate that the intermittent effect is stronger for two-dimensional analysis.It is not contradictory with jet-like multiparticle production mechanism. However,the analytic results of other methods show that the azimuthal structure seems to be of stochastic nature and no evidence of the jet-like multiparticle production mechanism is observed.     

Two-dimensional wavelet analysis of simulated angular distributions of particles in collisions of relativistic nuclei

A method for analysis of a multiparticle event with a complicated structure is developed on the discrete wavelet transform basis. Two-dimensional histograms corresponding to a given function and the events simulated by a generator of nucleus-nucleus collisions at the center-of-mass energy √s = 5.5 TeV are analyzed. It is shown that the wavelet analysis efficiently removes the background, distinguishes the ring structure of the multiparticle event, and allows the decrease in the threshold transverse jet energy required for the separation of the jet from the background.     

Near-side high-p T correlations: the ridge

An overview of results on near-side high-p _T triggered correlations in heavy-ion collisions at RHIC energy is presented. These correlations reveal a novel, long-range pseudo-rapidity correlation, commonly referred to as the ridge which is not present in p+p or d+Au collisions. The centrality, collision system, energy, transverse momentum, path length dependence as well as particle composition of the ridge will be discussed and compared with the properties of the jet-like component at near side. The data are also confronted with theoretical calculations.     

Color image encoding using fractional Fourier transformation associated with wavelet transformation

Color image encoding and decoding using fractional Fourier transformation (FRFT) associated with wavelet transformation (WT) are proposed in this paper, which is calculated using discrete fractional Fourier transformation and discrete wavelet transformation. A new method for color image encoding and decoding is given. Some examples of computer simulation results are proposed and verified.     

子波变换提取图像的边缘及角点信息

本文详细介绍Ｍｅｘｉｃａｎ－ｈａｔ子波变换的定义和基本特性，通过选取不同的子波函数，提取图像的边缘与角点信息。     

The four-jet structure of large transverse momentum events inpp interactions at the ISR

Deep inelastic proton-proton collisions have been recorded with the Split-Field-Magnet Detector (SFM) at the CERN Intersecting Storage Rings (ISR) by triggering on a single particle at high transverse momentum. Full reconstruction of the charged particles in these collisions was performed. In this paper we demonstrate the existence of a structure comprised of four jet-like clusters, two longitudinal and two transverse with respect to the beam, as would be expected from hard scattering of proton constituents.     

Leading-particle suppression and surface emission in nucleus-nucleus collisions

After a short summary of the predictions of the Parton Quenching Model (PQM) for the nuclear modification factor and its centrality dependence in Au?Au collisions at RHIC, we concentrate on back-to-back jet-like correlations at high transverse momentum. We illustrate how this probe is biased by the surface effect.     

Jet-like structures in photoelectron angular distributions

The photoelectron angular distributions (PADs) of hydrogen atoms in an intense laser field of linear polarization are studied using the S-matrix theory in the length gauge. The PADs show main lobes along the laser polarization and jet-like structures sticking from the waist of main lobes. Our previous prediction, based on a nonperturbative scattering theory of photoionization developed by Guo et al, showing that the number of jets on one side of PADs may increase by one, three, or other odd numbers and may decrease by one when one more photon is absorbed, is confirmed by this treatment. Within the strong-field approximation, good agreement is obtained between these two quite different treatments. We further study the influence of the Coulomb attraction to PADs, by taking a Coulomb--Volkov state as the continuum state of photoelectrons. We find that under the influence of the Coulomb attraction, the PADs change greatly but the predicted phenomena still appear. This study verifies that the jet-like structures have no relation with the angular momentum of photoelectrons.     

Angular correlation studies of heavy-particle impact excitation of atoms

A review is given of recent developments of angular correlation studies of heavy-particle impact excitation of atoms and molecules. After a brief discussion of the basic principles of experimental methods a theory of measurement of angular correlations from heavy-particle atom collisions is outlined in the following way. By applying angular correlation measurements a subensemble from the collision processes is selected which is described by state and scattering parameters. These parameters (scattering amplitudes and their phases, alignment and orientation, state multipoles and coherence parameters) can be connected with the experimental angular correlation data. Results from heavy-particle angular correlations have been discussed in separate sections with ions or atoms as projectiles; subsections are dealing with charge exchange excitation, excitation of autoionizing states, direct and simultaneous excitation of target and projectile particles. The angular correlation parameters are very sensitive to the detailed excitation mechanisms and quasi-molecular parameters in heavy-particle atom collisions. The majority of data available so far were obtained from simple projectile-target systems such as one-electron atom systems and are rare gas atoms. Attention is drawn to possible spin-orbit effects in the analysis of angular correlations from collisions between very heavy atomic particles.     

红外光谱的煤精类文物材质判别方法

我国是世界上最早使用煤及煤精的国家之一,但对考古出土煤精文物的研究发现,煤精文物原材料的质地常常偏离宝石学中对有机宝石煤精的定义。在此提出“煤精类文物”的概念,将以往出土文物中如褐煤、烛煤等与煤精文物材质近似但不同的材料归至同一文化概念中。目前对于煤精类文物制品的科学研究仍存在较大空白,其中最为基础的材质种类判别也没有科学的判断方法。以陕西周原贺家墓地、陕西咸阳岩村墓地、新疆吐鲁番胜金店墓地、新疆伊犁吉仁台沟口遗址四个遗址出土的16件煤精制品和原料为研究对象,初步探索漫反射傅里叶变换红外光谱在出土煤精类文物成分分析中的应用。结果表明,不同遗址出土的煤精类文物的红外谱图有较为明显的不同,同一遗址出土的煤精类文物的红外谱图在特征波段具有相似性,不同遗址煤精类文物则差异明显。使用Norris二阶导数法对红外光谱进行处理,提高吸收峰分辨率,为精细研究提供信息,选择特殊红外光谱参数I=A_{820 cm-1}/A_{2 870 cm-1}定量分析不同样品的红外光谱,结合静水称重得到的部分样品的密度信息,对出土的煤精类文物制品材质的煤化程度初步判断。结合红外光谱特征波数的强度进一步通过主成分分析解释煤精类文物的红外光谱信息,来自不同遗址的煤精类文物样品在主成分分析得分图中得到了良好的区分,并且可以与特殊红外光谱参数I判别的初步结论互相对应。验证了以漫反射傅里叶变换红外光谱为主的无损分析方法在煤精类文物材质判别中应用的可行性;若结合不同产地煤精矿样红外光谱,则可以为煤精类文物产地判别提供研究方法。     

Origin of complex fragments from32S+natAg reaction at 37.5 A·MeV

Fragment emission from collisions of³²S with^natAg at 37.5 A·MeV has been studied with the 4π multi-detector AMPHORA. Production of intermediate mass and heavy fragments as well as of light charged particles has been measured. The total charged particle multiplicity and polar angular distributions have been used to select various classes of collisions. Analysis of angular and energy distributions of fragments and light particles in central collisions indicates the formation of a hot source (excitation energy of≈4.4 A·MeV) with an additional contribution from a preequilibrium process at more forward angles. Azimuthal angle correlations of He-Li, Li-Li, B-B, and C-C pairs have been used as a tool to study the origin of complex fragments. Data at backward angles are well described by considering a thermalized emitter with an angular momentum around 70? and a fragment emission time of the order of 200 fm/c. A microscopic approach of BNV type confirms these emission times and angular momenta indicating the persistence of an incomplete fusion process responsible for the emission of complex fragments at backward angles.     

Gluon jet-like structure in the upsilon decay

The properties of hadronic jets in e⁺ e^– annihilation in quantum chromodynamics have been studied. Motivated by the observation of the hadronic jets (arising from quark jets), the partial cross sections from the two-gluon jet-like events are calculated perturbatively. Estimates for the jet angular radius and its energy dependence are discussed.The author would like to thank Dr. Mubarak Ahmad for his guidance and encouragement.     

Wavelet correlations in hierarchical branching processes

A study of correlations in tractable multiparticle cascade models in terms of wavelets reveals many promising features. The selfsimilar construction of the wavelet basis functions and their multiscale localization properties provide a new approach to the statistical analysis and analytical control of hierarchically organized branching processes. The exact analytical solution of several discrete models shows that the wavelet transformation suppresses redundancy in the correlation information. Wavelet correlations can be naturally interpreted as correlations between structures (clumps) living on different scales.     

Further evidence for nuclear rolling friction acting in heavy-ion induced reactions

Recent experimental results on heavy-ion fusion cross sections for asymmetric systems and on angular momentum transfer in damped collisions are shown to be well described, if rolling friction is explicitly taken into account. Its neglect in various other trajectory calculations leads to a significant underestimate of the fusion cross section as well as of the transferred angular momentum.     

离散小波变换耦合静电场理论的图像快速伪造检测算法

为了解决当前图像伪造检测算法主要是在图像空域中定位伪造区域,难以降低图像维数,使其复杂度大;且不能有效检测几何变换篡改形式的伪造区域,导致其鲁棒性不佳的不足,本文提出了离散小波变换耦合静电场理论的图像伪造检测算法。首先,引入离散小波变换,提取伪造图像的低频子带,降低图像空间;再基于静电场理论,将提取子带映射到虚拟电场中,提取鲁棒性较强的特征,利用Radix排序算法对特征完成重组,形成特征矩阵;最后,定义相同仿射变换,并用其处理排序矩阵,完成伪造区域检测。实验测试结果显示：与当前的移动复制伪造检测技术相比,本文算法具有更高的定位效率与检测精度;同时拥有较强的鲁棒性,有效抗击几何变换篡改。     

Experimental verification of a cross effect between heat and momentum transport in a molecular Knudsen gas

The pressure difference induced by a magnetic field in a heat conducting Knudsen gas is investigated. The effect results from molecular angular momentum polarization produced in molecule-surface collisions. Data obtained for N₂ are well described in terms of gas kinetic theory.     

Partial-wave decomposition of the ionization continuum accessed by vibrational autoionization of the NO 14s ( nu = 1, N = 20, N(+)(R) = 20) level

Rotationally resolved photoelectron angular distributions from vibrational autoionization of the NO 14s ( nu = 1, N = 20, N(+)(R) = 20) level are measured by photoelectron spectroscopy, and they are analyzed using a theoretical model based on first-order coupling between the Rydberg level and the ionization continuum. The analysis reveals that lambda-changing collisions and l-changing collisions between the molecular-ion core and the outgoing electron are comparable in magnitude and account for 40% of the partial waves produced in the ionization continuum.