Study of multiparticle spikes in central 4.5A GeV/c C-Cu collisions

An analysis of local fluctuations, or spikes, is performed for charged particles produced in central C-Cu collisions at 4.5 GeV/c/nucleon. The distributions of spike centers and the maximum density distributions are investigated for different narrow pseudorapidity windows to search for multiparticle dynamical correlations. Two peaks over statistical background are observed in the spike-center distributions with the structure similar to that expected from the coherent gluon radiation model and recently found in hadronic interactions. The dynamical contribution to maximum density fluctuations is obtained to be hidden by statistical correlations, although behavior of the distributions shows qualitative agreement with that from the one-dimensional intermittency model. The observed features of the two different approaches, coherent vs. stochastic, to the formation of the local dynamical fluctuations are discussed.     

Verification of the model of a collision of a 800-GeV proton with an emulsion-nucleus tube

The production of quark-gluon plasma is discussed within the hydrodynamic theory of multiparticle hadron production in head-on collisions of nucleons with nucleons and nuclei. In searches for collisions of a proton with a tube of a track-emulsion nucleus, the use of parametrically invariant quantities is proposed. An experimental verification of statistical models involving qualitatively different pseudorapidity distributions of weakly ionizing secondary particles is performed. The results of this verification are discussed.     

Study of multiparticle azimuthal correlations in central CNE, MgMg, CCu, and OPb interactions at energy of 3.7 GeV per nucleon

Azimuthal correlations between protons and between pions have been investigated in central CNe, MgMg, CCu, and OPb collisions at an energy of 3.7 GeV/nucleon. Negative (back-to-back) correlations have been observed for protons in CNe, CCu, and for π ^? mesons in CNe and MgMg collisions. For π^? mesons, positive (side-by-side) azimuthal correlations have been observed for heavy systems of CCu and OPb. The Quark-Gluon String Model satisfactorily describes the experimental results both for protons and π^? mesons.     

Comparison of particle production in Pb(158 GeV/nucleon)-AgBr collisions with the VENUS and FRITIOF models

Data on multiparticle production in interactions of 158 GeV/nucleon lead ions with the heavy nuclei in emulsions (Ag,Br) are compared with the predictions of the VENUS and FRITIOF models. It is found that total multiplicities of produced charged particles are reasonably well reproduced by both models. On the other hand, discrepancies between the data and the predictions are observed for the forward charge and pseudorapidity distributions. Furthermore, dynamical fluctuations, revealed in the data by application of the method of factorial moments, are absent from the model simulations. The dynamical fluctuations observed in the data can be at least partly due to Bose-Einstein correlations.     

Erratic fluctuations in 14.5A GeV/c 28Si−AgBr Collisions

Analysis of multiparticle production data on 14.5A GeV/c ²⁸Si?AgBr collisions in terms of erraticity is carried out and the results are compared with those obtained from the Monte Carlo simulated data (using event generator HIJING). It is shown that like the multifractal spectrum through G _qmoments, erraticity spectrum may also be constructed from the observed power-law behaviour of the erraticity moments. Further, for examining the dominance of statistical fluctuations over the erraticity behaviour, correlation-free Monte Carlo events are simulated and analyzed. A comparison of the experimental and simulation results indicates that the fluctuations observed in the case of experimental data are not only because of the statistical reasons, but may have some dynamical origin.     

高能重离子碰撞多粒子产生的热力学模型研究

评述了高能重离子碰撞中多粒子产生的热力学模型,并根据该模型的最新发展,研究了有关高能核－核碰撞中簇射粒子的赝快度分布问题． The thermodynamic models for multiparticle production in high energy heavy ion collisions are reviewed.According to the recent developments of the thermodynamic models,the pseudorapidity distributions of shower particles produced in high energy nucleus nucleus collions are investigated.     

Multiplicity and pseudorapidity distributions of charged particles from32S induced heavy ion interactions at 200A GeV

Multiplicity and pseudorapidity distributions have been measured for³²S+Al, Cu, Ag and Au at 200A GeV. The widths of the pseudorapidity distributions increase from central to peripheral collisions. The main contribution is assumed to come from the increasing fraction of charged particles stemming from the fragmentation of the target for peripheral collisions as compared to central collisions. On the average 170–180 charged particles per unit of pseudorapidity are attained for the most central³²S+Au events at the maximum of the distribution. The target dependence of the yield of charged particles for central collisions is investigated. In the target rapidity region the yield is directly proportional to the target mass. The transverse energy per charged particle has been studied as a function of centrality and pseudorapidity. The experimental results are compared to the results from the Monte-Carlo model VENUS 3.11 which includes rescattering among secondaries. A comparison between different centrality triggers is made.     

Factorial cumulant moments and correlation integrals in pp collisions at 400 GeV/c

The pseudorapidity distribution of charged particles produced in pp collisions at 400 GeV/c was measured by using LEBC films offered by CERN NA27 collaboration. The scaled factorial cumulant moments have been calculated. The results show that the second order cumulants have positive values, while the cumulants of higher order are consistent with zero except for the situation ofn _ch ≥ 4 events, where the third-order cumulants have positive values beyond the statistical uncertainties. It means that the observed increase of the higherorder factorial momentsF _q is almost due to the dynamical two-particle correlation in pp collisions at 400 GeV/c. The cumulant moments also have been calculated by star correlation integrals. It significantly reduced the statistical errors, especially for higher order cumulants. From Monte Carlo events with the same single particle spectrum and no correlations, we observed that for broad mixed-multiplicity distributions, a significant part ofK ₂ is coming from the single-particle fluctuation due to the fluctuating multiplicity.     

400GeV/c pp碰撞间歇指数的测量

利用CERNNA27合作组提供的LEBC泡室照片对400GeV/c pp碰撞产生的带电粒子赝快度分布进行了测量.计算了标度阶乘矩.得出间歇指数随矩阶数的增加而增加,随平均多重数的增加而变小;反常分形维数dq随q的增加而增加.这表明在强子-强子碰撞中多粒子产生具有自相似级联的性质.     

Nuclear effects in multiparticle production in 800 GeV and 400 GeV proton-nucleus interactions

We study nuclear effects in multiparticle production in proton-emulsion nuclei interactions at 800 GeV and 400 GeV. The observed pseudorapidity distributions are compared with the predictions of a simple quark model. The predicted dependence of the ratio of the normalised multiplicity distribution of the produced shower particles in hadron-nucleus (hA) to hadron-hadron (hh) interactions on the mean number of inelastic collisions in the central region is in good agreement with the experimental data.     

Correlation and fluctuations in relativistic nucleus-nucleus collisions

Correlation and fluctuations are now well accepted analysis techniques in heavy-ion collisions at relativistic energies. At the current stage of RHIC exploration, matter in bulk and many of the physics questions about the final stage of collisions are addressed with the help of correlation techniques. In the present work after a general introduction to the underlying formalism to the exotic phenomena of correlation and fluctuations, discussion on various parameters disentangling dynamical fluctuations is presented. Analysis to investigate dynamical fluctuations and correlation is carried out in terms of F _q - and G _q -moments. A study of various other parameters involving multiplicity and pseudorapidity of relativistic charged particles produced in high energy nuclear interactions reveals the presence of correlation and fluctuations in particle production in these collisions. The experimental data on 14.5A GeV/c ²⁸Si-nucleus interactions has been analyzed. A parallel analysis of correlation free data generated using MC-RAND Monte Carlo code, UrQMD data and for the HIJING generated events has also been carried out.     

400GeV/c pp碰撞类环事例的产生

利用400GeV/c pp碰撞产生的带电粒子赝快度分布的实验数据,研究了类环事例的产生机制.结果表明在一有限的时间-空间范围内相干胶子辐射是类环事例的一种可能的产生机制,但肯定不是主要的.     

Production of Ring-like Events in pp Collisions at 400GeV/c

The production mechanism of ring-like events has been investigated by using the data of pseudorapidity distribution of charged particles produced in pp collisions at 400GeV/c. The results show that the model of coherent gluon emission within a finite region of space-time is a possible production mechanism of ring-like events, but certainly not dominant.     

高能多粒子末态的多重分形维数与动力学起伏强度

研究了多重分形维数与动力学起伏强度的关系,给出了一个能直接描述高能多粒子末态动力学起伏强度的特征参量,并指出了这一参量的适用范围以及在实际高能实验中的应用.     

NeXSPheRIO results on elliptic-flow fluctuations at RHIC

By using the NeXSPheRIO code, we study the elliptic-flow fluctuations in Au + Au collisions at 200 A GeV. It is shown that, by fixing the parameters of the model to correctly reproduce the charged pseudorapidity and the transverse-momentum distributions, reasonable agreement of 〈v ₂〉 with data is obtained, both as function of pseudorapidity as well as of transverse momentum, for charged particles. Our results on elliptic-flow fluctuations are in good agreement with the recently measured data on experiments. The text was submitted by the authors in English.     

(sNN)1/2=200 GeV的d+Au碰撞中末态带电粒子赝快度分布的对心度依赖性

将核子-核子碰撞末态带电粒子的生成源分为二元核子 核子碰撞与带头粒子两部分, 给出了末态带电粒子的赝快度分布与入射能量间的解析关系。 以此为基础, 将核 核碰撞末态带电粒子的生成源分为二元核子-核子碰撞、 带头粒子与旁观者3部分, 建立起了以碰撞参数与束流能量为自变量的末态带电粒子的赝快度分布, 并用其分析了BNL-RHIC-PHOBOS合作组在sNN=200 GeV的不同d+Au对心度碰撞中所做的实验测量。 所得结果与实验符合得很好。 We divide the particle generating sources in nucleon-nucleon collisions into two parts: binary collisions and leading particles, and present the analytical relation between charged particle pseudorapidity distributions and incident energy. On the basis of this work, we classify the particle generating sources in nucleus-nucleus collisions into three parts:binary collisions,leading particles and spectators,and formulate the charged particle pseudorapidity distributions as the function of incident energy and impact parameter. We then analyze with the model the experimental measurements in d+Au collisions at sNN=200 GeV. The theoretical results are well consistent with experimental data.     

Fragmentation of target spectators in ultrarelativistic heavy ion collisions

We demonstrate that the assumption that target spectators fragment isotropically in a gently moving coordinate system is in agreement with pseudorapidity distributions, measured in central ultrarelativistic heavy ion collisions of projectile energy from 14.5A GeV to 200A GeV. Target spectator remnants might be excluded from measurement by introducing a low energy cutoff for the accepted particles at approximately 200 MeV. An approximate scaling is presented for the pseudorapidity distribution of the target spectator fragments. Theoretical tools used for studying intermediate energy heavy ion collisions seem to be applicable in describing target spectator fragmentation in ultrarelativistic heavy ion collisions.     

4.5AGeV/c 24Mg与核乳胶碰撞中簇射粒子的赝快度分布

报道了4.5AGeV/c ²⁴Mg与核乳胶碰撞中产生的簇射粒子的赝快度分布,结果表明,分布宽度和峰值位置明显依赖于靶核尺寸.用柱模型对赝快度分布进行了分析,MonteCarlo方法计算得到的结果基本符合实验数据的走向,并重现了实验数据中的涨落现象.     

Charged particle density distributions in Au + Au collisions at relativistic heavy-ion collider energies

Charged particle pseudorapidity distributions have been measured in Au+ Au collisions using the BRAHMS detector at RHIC. The results are presented as a function of the collision centrality and the center of mass energy. They are compared to the predictions of different parton scattering models and the important role of hard scattering processes at RHIC energies is discussed. Keywords. Relativistic heavy-ion collisions; charged hadron production; pseudorapidity distributions; centrality dependence; hard scattering processes.     

Pseudorapidity Distribution of Shower Particles in 24Mg-Emulsion Collisions at 4.5A GeV/c

The pseudorapidity distribution of shower particles produced in the ²⁴Mg-emulsion collisions at 4.5A GeV/c is reported in this paper. The dependences of the distribution width and the peak position on the target size are observed.The pseudorapidity distribution of shower particles for the events with low target multiplicity (light target) is narrower than that with high target multiplicity (heavy target). The maximum probability pseudorapidity for light target is greater than that for heavy target. The experimental data is analyzed by using the cylinder model suggested by Liu et al. The Monte Carlo results based on Liu's cylinder model are approximately in agreement with the experimental tendency and fluctuation.