颗粒相干发射源的2π和3π玻色-爱因斯坦关联

在假设由同一颗粒发射的π介子为相干发射的条件下, 给出了颗粒发射源模型的2π及3π关联函数, 发射源的混沌性随颗粒数目的增加而增大. 此外, 对颗粒相干发射源及部分相干高斯源的归一化纯3π关联进行比较, 发现当2π关联的混沌性参量小于0.8时, 两种发射源的归一化纯3π关联值在小Q₃区域有明显差别.     

Source parameters deduced from Bose-Einstein correlations of two and three soft pions in symmetric heavy-ion interactions at 650 A MeV

The analysis of Bose-Einstein correlations for systems of two and three low-momentum pions in interactions of Au+Au and Nb+Nb at 650 A MeV kinetic energy are presented. The data were taken with the Plastic Ball spectrometer. The pion-emitting source sizes obtained from specific three-pion correlations are significantly smaller than those extracted from two-pion correlations. The dependence of the source parameters on the multiplicity of produced pions was examined. The low-p _t pions are emitted from a larger region than the high-p _t ones.     

Role of Δ exchange for p annihilation into two-pion and three-pion channels

p annihilation into two pions and three pions is studied in a baryon exchange model. Annihilation diagrams involving nucleon as well as Δ-resonance exchanges are included consistently in the two- and three-pion channels. Effects from the initial-state interaction are fully taken into account. A comparison of the influence of the Δ exchange on the considered annihilation channels is made and reveals that its importance for three-pion annihilation is strongly reduced as compared to two-pion annihilation. It is found that annihilation into three uncorrelated pions can yield up to 10% of the total experimentally observed three-pion annihilation cross-section. Received: 16 January 2002 / Accepted: 20 February 2002     

Note on Bose-Einstein correlations of three pions in symmetric heavy-ion interactions at 650 a MeV

In a recent article published in this journal it is stated that a specific three-pion effect is found in an experiment studying Au+Au collisions. The aim of this note is to show that these new data are compatible with two-pion effects leaving no room for a specific three-pion effect. This is in accordance with three-pion interferometry results from pp and e⁺ e^? collisions at a high energy.     

Multi-pion Bose-Einstein correlation effects on three-pion interferometry

Multi-pion correlations effect on three-pion interferometry is studied. It is shown that multi-pion correlations decrease both the apparent radius of the source and the coherent source parameter derived from three-pion interferometry. The data of OPAL group are discussed.     

An energy sum constraint of event mixing for Bose-Einstein correlations in reactions with ππX final states around 1 GeV

We present a new event mixing technique for measuring two-pion Bose-Einstein correlations(BEC)in reactions with only two identical bosons among three final state particles.This new mixing method contains a missing mass consistency(MMC)cut and an energy sum order(ESO)cut.Unlike the previous proposed pion energy cut,which abandons nearly half the original events,the ESO cut does not eliminate any original events and hence improves the statistics of both original events and mixed events.Numerical tests using theγp→π~0π~0p events around1 Ge V are carried out to verify the validity of the ESO cut.This cut is able to reproduce the relative momentum distribution of the original events in the absence of BEC effects.In addition,its ability to observe BEC effects is tested by an event sample in the presence of BEC effects.Simulation results show the BEC effects can be observed clearly as an enhancement in the correlation function,and the BEC parameters extracted by this event mixing cut are consistent with the input BEC parameters.     

Effects of source opacity and expansion on two-pion Bose-Einstein correlations

We examine two-pion Bose-Einstein correlations for partially coherent particle-emitting sources within quantum statistical formalism, where the sources are treated as classical currents with chaotic and coherent components. The two-pion correlation functions of the partially coherent sources contain a phase which is sensitive to the asymmetry of the source emission function. We investigate the influence of source opacity and expansion in high energy heavy ion collisions on the phase by Monte Carlo calculati...     

Two-Pion Interferometry at Small Relative Momentum Taking Account for Multi-Pion Correlations

A general expression for nπ correlation function is given when there are multi-pion correlations in the choices of correlated nπ and uncorrelated nπ. Using this expression, the two-pion interferometry at small relative momentum which takes account for multi-pion correlations is studied, the relations between the pion source parameters from the two-pion interferometry and the three- pion interferometry are obtained analytically, and comparison is made with the experimental results of central relativistic heavy ion collisions 1.8 A GeV Ar+Pb.     

TWO-PION INTERFEROMETRY FOR MULTI-PION EVENTS IN RELATIVISTIC HEAVY ION COLLISIONS

The effect of multi-pion correlations on two-pion interferomentry in a multi-pion event is studied.A new general two-pion interferometry method is developed,by taking into consideration of the effect of multi-pion correlations.Data for 1.8A GeV Ar+Pb central collisions at the Bevalac streamer chamber are analysed by using this new method.     

Model-independent source imaging using two-pion correlations in (2 to 8)a GeV Au+Au collisions

We report a particle source imaging analysis based on two-pion correlations in high multiplicity Au+Au collisions at beam energies between 2A and 8A GeV. We apply the imaging technique introduced by Brown and Danielewicz, which allows a model-independent extraction of source functions with useful accuracy out to relative pion separations of about 20 fm. The extracted source functions have Gaussian shapes. Values of source functions at zero separation are almost constant across the energy range under study. Imaging results are found to be consistent with conventional source parameters obtained from a multidimensional Hanburg-Brown-Twiss analysis.     

Hadronic expansion dynamics in central Pb+Pb collisions at 158 GeV per nucleon

Two-particle correlation functions of negative hadrons over wide phase space, and transverse mass spectra of negative hadrons and deuterons near mid-rapidity have been measured in central Pb+Pb collisions at 158 GeV per nucleon by the NA49 experiment at the CERN SPS. A novel Coulomb correction procedure for the negative two-particle correlations is employed making use of the measured oppositely charged particle correlation. Within an expanding source scenario these results are used to ext ract the dynamic characteristics of the hadronic source, resolving the ambiguities between the temperature and transverse expansion velocity of the source, that are unavoidable when single and two particle spectra are analysed separately. The source shape, the total duration of the source expansion, the duration of particle emission, the freeze-out temperature and the longitudinal and transverse expansion velocities are deduced. Received: 25 November 1997 / Published online: 24 March 1998     

Three-pion correlations for studying partial coherence in nuclear collisions

Use of three-particle correlations provides a unique tool for studying partial coherence in relativistic heavy-ion collisions. Here a theory is presented for multiple coherent source components of partially coherent pion radiation. Results are given for the relative probabilities of emission of one, two, or three pions. The calculations on the relation between two- and three-pion correlators give some evidence, when compared with available experimental data, for the existence of partial coherence and multiple coherent components in heavy-ion collisions.     

Some forgotten features of the Bose-Einstein correlations

Notwithstanding the visible maturity of the subject of Bose-Einstein correlations (BEC), as witnessed nowadays, we would like to bring to one’s attention two points which apparently did not receive the attention they deserve: the problem of the choice of the form of C ₂(Q) correlation function when effects of partial coherence of the hadronizing source are to be included and the feasibility to model effects of Bose-Einstein statistics, in particular, the BEC, by direct numerical simulations. The text was submitted by the authors in English.     

Analytic representation for3He form factors

A modifiedN/D method is applied for the cases of³He charge and magnetic form factors. Anomalous cut positions are computed using possible exchanges at the photon-³He electromagnetic vertex. and one of them is found att _a =0.0618 GeV². TheD-function is used to parametrize the two-pion cut while theN-function is taken to represent the effect of an anomalous or the three-pion cut. Excellent fits to the available experimental data on charge and magnetic form factors are obtained and several useful information on the form factors computed.     

球形夸克-胶子等离子体演化源的π干涉学分析

本文对球形演化的夸克–胶子等离子体膨胀源进行了2π干涉学分析.夸克–胶子等离子体的演化由相对论流体力学和熵密度的物态方程描述,而2πHanbury-Brown-Twiss(HBT)关联函数由量子几率振幅的路径积分公式计算.研究结果表明,由2π干涉学得到的源的空间参量敏感地依赖于π介子发射源的相空间分布,源的膨胀速度导致HBT半径变小,并会改变HBT半径与冻结温度之间的关系.     

对高重子数密度粒子发射源的干涉学分析

应用量子路径积分的方法,分析了高能重离子碰撞产生的高重子数密度粒子发射源的２K和2π干涉学（hanbury Brown Twiss,HBT关联）。利用相对论流体动力学描述源的演化,采用的状态方程包含QGP到强子相的一级相变和对强子气体的体积修正。在２π关联的计算中考虑了激发态粒子衰变和多重散射效应,并将其HBT关联半径和寿命与传统热冻结模型的结果进行了对比。计算表明,早期化学冻结产生的K介子的HBT关联半径比２π关联的HBT关联半径小。激发态粒子的衰变使HBT关联半径和寿命增加,而多重散射对HBT关联的结果几乎没有影响。Using quantum path integral formulae, we examined the two kaon and two pion Hanbury Brown Twiss (HBT) interferometry for the particle emitting source with high baryon density. The evolution of the source is described by relativistic hydrodynamics. We use an equation of state of first order transition from QGP to hadronic phase and consider a volume correction for the hadronic gas. The two pion HBT results with effects of excited particle decay and multiple scattering were investigated and compared with those for conventional thermal freeze out (TFO) model. We found that the two kaon HBT radius was smaller than those of the two pion interferometry. The particle decay increases the HBT radius and lifetime, while the effect of multiple scattering on HBT results can be neglected.     

Proton-pion and two- pion correlations in eA interactions

We report here the results on studying of proton-pion and two-pion correlations in eA interactions at 5 GeV. Kinematic correlations were studied as a function of the two-particle opening angle, their momenta and proton multiplicity. The universal properties of correlation functions were found with respect to different particle species. Interferometry method was used to determine the size of the interaction region.     

Coulomb and strong interactions for Bose-Einstein correlations

We present an analytical formula for the Bose-Einstein correlations (BEC) which includes effects of both Coulomb and strong final state interactions (FSI). It was obtained by using Coulomb wave function together with the scattering partial wave amplitude of the strong interactions describing data on thes-wave phase shift. We have proved numerically that this method is equivalent to solving Schrödinger equation with Coulomb and thes-wave strong interaction potentials. As an application we have analysed, using our formula which includes the degree of coherence and the long range correlation, the data fore ⁺ e ^? annihilations. We have found that the degree of coherence present in our formula approaches approximately unity whereas the long range correlation parameter becomes approximately zero. These results suggest that the physical meanings of the fractional degree of coherence and the long range correlation observed in various other analyses can most probably be attributed to FSI.     

Effect of Coulomb correlations in a variable-valence impurity system and phonon drag on the thermoelectric constants in two-dimensional systems

The temperature behavior of the longitudinal Nernst-Ettingshausen coefficient in 2D systems is studied theoretically taking account of phonon drag and Coulomb correlations in a system of mixed-valence impurities at low temperatures. It is shown that the effect changes sign at the transition from entrainment to scattering by a correlated system of impurity centers. A sign change does not occur in the case of scattering by randomly distributed impurity centers. This temperature behavior of the Nernst-Ettingshausen coefficient is due to the radical rearrangement of the impurity system as a result of strong Coulomb correlations present in a system of impurities with mixed valence. As a result, the character of the scattering of charge carriers by the correlated system of charge centers changes substantially. Fiz. Tverd. Tela (St. Petersburg) 40, 553–556 (March 1998)