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运用修正的超相对论量子分子动力学模型研究了交变梯度同步加速器(AGS)能区Au+Au碰撞中的核阻止效应. 该模型考虑了形成和"预形成"粒子的平均场势、核子-核子弹性散射反应截面的介质修正和碎块形成的判断条件. 研究发现: 在AGS能区, 核阻止效应受到形成和“预形成”粒子的平均场势和核子-核子弹性散射反应截面介质修正的影响; 在中心快度区自由质子的产额偏大, 考虑新的碎块形成判断条件后, 此模型的理论计算结果与自由质子的实验结果符合得很好.
关键词:
超相对论量子分子动力学模型
交变梯度同步加速器能区
Au+Au碰撞
核阻止效应 相似文献
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在对超高能区宇宙线产生的广延大气簇射的模拟计算中注意到,质子—空气核碰撞中的受伤核子数分布和非弹性截面对于簇射的纵向发展有着重要的影响.本文依据符合现有加速器能区的有关质子—质子作用截面的经验公式,对超高能区的质子与空气核碰撞的受伤核子数分布和非弹性截面做了计算. 相似文献
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大入射能量范围内重离子输运过程的动力学性质研究 总被引:1,自引:0,他引:1
基于一个改进的微观动力学输运模型——极端相对论量子分子动力学(UrQMD), 较为系统地研究了从SIS能区到AGS和SPS能区, 再到RHIC能区, 入射能量跨5个数量级的重离子核反应及多个人们感兴趣的实验观测量, 如粒子产额、 集体流、 核阻止以及两粒子HBT关联等。研究表明, 不论单粒子观测量, 还是两粒子关联观测量, 都能自洽地由同一个输运模型加以描述。Based on one updated microscopic transport model Ultra relativistic Quantum Molecular Dynamics (UrQMD) with modifications of both potentials and two body scattering cross sections, quite a few interesting observables, such as yields, collective flows, the nuclear stopping, and the HBT two particle interferometry, are systematically investigated for heavy ion collisions within a large beam energy regime of five orders of magnitude (from SIS, AGS, SPS up to RHIC). It is shown that a consistent explanation can be received from both single particle and two particle related observables. 相似文献
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在总结双柱模型计算结果的基础上, 用该模型对交变梯度同步加速器(AGS)和相对论性重离子对撞机(RHIC)能区核-核碰撞中的领头粒子效应进行了统一分析. 结果表明:在AGS和RHIC能区, 不同中心性核-核碰撞中带电粒子(赝)快度分布的不同, 主要由领头粒子的贡献影响; 如果扣除领头粒子的贡献, 不同中心性核-核碰撞中带电粒子的(赝)快度分布有相同的形状. 相似文献
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研究了RHIC和LHC能区的Au-Au和Pb-Pb周边重离子碰撞中,来自光子-核子相互作用产生的大横动量双轻子。利用微扰QCD 参数化和Weizs?cker-Williams近似计算了双轻子的产率。经过与领头阶和碎裂过程的双轻子产生数值计算结果相比较,光-核碰撞过程产生的大横动量双轻子在RHIC能区是可忽略的。但是在LHC能区,光-核碰撞在大横动量区域是周边重离子碰撞的一个重要的双轻子源。 相似文献
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Wanchaloem Poonsawat Ayut Limphirat Dai-Mei Zhou Yu-Liang Yan Pornrad Srisawad Chinorat Kobdaj Yupeng Yan Ben-Hao Sa 《Few-Body Systems》2014,55(8-10):1041-1043
The parton and hadron cascade model, PACIAE 2.0, is employed to calculate the net-proton nonstatistical moments in pp collisions at RHIC and LHC energies. By analyzing the results in the full phase space, it is found that the nonstatistical moments and moments products are significantly dependent on the collision energy. It is suggested that the net-proton nonstatistical moments in pp collisions may be studied in partial phase spaces with the PACIAE model. 相似文献
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It is found that Collective Flow Model (CFM) which can successfully analyze charged particle distributions at AGS and lower
SPS (less than 20 GeV/n), fails to analyze that of RHIC. The tail of distribution of charged particle at RHIC has a jump away
from the collective model calculation as the energy increase. Thermalization Component Model (TCM) is presented basing on
collective flow to study the multiplicity distributions at RHIC in this paper. It is realized that the limitation of phase
space of collective flow can denote that of thermalization region. By comparing the contributions of particle productions
from thermalization region at different energies and different centrality, we can deep our study on the feature of collective
movement at RHIC. 相似文献
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By means of the AKK08 fragmentation function, the net-proton transverse momentum (pT) spectra in A+A collisions are studied with two phenomenological models based on the Color Glass Condensate formalism. After a x2 analysis of the experimental data from BRAHMS, the normalization constant C is extracted at RHIC energies of √SNN =62.4 and 200 GeV, and the theoretical results of the net-proton pT spectra at selected rapidities are also given. It is shown that the theoretical results are in good agreement with the experimental data. Finally, assuming the constant C should have an exponent dependence of √SNN, we also predict the theoretical results of net-proton pT spectra at LHC energies of √SNN = 2.76, 3.94, and 5.52 TeV. 相似文献
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A new geometrical scaling method with a gluon saturation rapidity limit is proposed to study the gluon saturation feature of the central rapidity region of relativistic nuclear collisions. The net-baryon number is essentially transported by valence quarks that probe the saturation regime in the target by multiple scattering. We take advantage of the gluon saturation model with geometric scaling of the rapidity limit to investigate net baryon distributions, nuclear stopping power and gluon saturation features in the SPS and RHIC energy regions. Predictions for net-baryon rapidity distributions, mean rapidity loss and gluon saturation feature in central Pb+Pb collisions at the LHC are made in this paper. 相似文献
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Hongyan Yang for the BRAHMS Collaboration 《Czechoslovak Journal of Physics》2006,56(1):A27-A37
The main experimental results obtained by the BRAHMS experiment at Relativistic Heavy Ion Collider (RHIC) for Au+Au collisions at \(\sqrt {s_{NN} } \) =62.4, 200 GeV and d+Au collisions at \(\sqrt {s_{NN} } \) = 200GeV are presented. The m T spectra and the Gaussian-like rapidity densities of produced pions and kaons in Au+Au central collisions at \(\sqrt {s_{NN} } \) = 200 are GeV shown, and their rapidity densities are compared with results from models. The net-proton yield in the same system is compared with that from AGS and SPS energies to study the high energy collision scenario-transparency and stopping. The rapidity, energy and centrality dependence of the nuclear modification factors in both systems are compared with models to differentiate between the initial and final state effect. 相似文献
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We study the phase structure of QCD matter in the framework of a multiphase transport model by implementing a strong local parton density fluctuation scenario. Our calculations on the beam energy dependence of net-proton high moment show that local parton density fluctuation only has a small effect. But it becomes important when all baryons are included. We then study the effect on elliptic flow and find that an enhanced local parton density fluctuation leads to a significant effect on protons but a small effect on pions. Our study provides a reference of transport dynamics on QCD phase transition phenomena and will be relevant for the upcoming phase II of the beam energy scan program at RHIC. 相似文献
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The features of nuclear stopping power and multi-hadron production systematically are studied by making an analysis of rapidity
distributions of pion and proton at AGS, SPS and RHIC in this work. It is found that nuclear stopping power increases linearly
with project rapidity y
p at AGS and SPS, but that is not liner at RHIC. It is argued that the average rapidity loss is saturated at central rapidity
region at RHIC. For pion distribution, it is found that the phase space of pion distribution distributes uniformly in the
longitudinal direction, and a linear relationship of 〈βγ〉L with log√s is given at AGS and SPS. Non-uniform flow model may explain the features of the distribution at AGS and SPS, but may not
explain those of at RHIC.
Supported by the Excellent Youth Foundation of Hubei Scientific Committee (Grant No. 2006ABB036), the Educational Commission
of Hubei Province of China (Grant No. Z20081302), and the Natural Science Foundation of China Three Gorges University (Grant
No. 2003C02) 相似文献
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Olga Barannikova 《Acta Physica Hungarica A》2002,15(3-4):237-245
Preliminary results on antiproton and charged kaon spectra and the net-proton number at mid-rapidity are reported for Au+Au collisions at $\sqrt {s_{NN} } = 130$ GeV as measured by the STAR experiment at RHIC. Inverse slope parameters of the transverse mass distributions increase with the collision centrality, consistent with a strong radial flow. The antiproton and charged kaon extrapolated yields, normalized to the uncorrected negatively charged hadron yield, increase with the collision centrality. A finite but small number of net-baryons is found to be present at mid-rapidity. 相似文献
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G. Wolschin 《The European Physical Journal A - Hadrons and Nuclei》2006,29(1):113-118
In a Relativistic Diffusion Model (RDM), the evolution of net-proton rapidity spectra with
in heavy systems is proposed as an indicator for local equilibration and longitudinal expansion. The broad midrapidity valley
recently discovered at RHIC in central Au + Au collisions at
= 200 GeV suggests rapid local equilibration which is most likely due to deconfinement, and fast longitudinal expansion.
Rapidity spectra of produced charged hadrons in d + Au and Au + Au systems at RHIC energies and their centrality dependence
are well described in a three-sources RDM. In central collisions, about 19% of the produced particles are in the equilibrated
midrapidity region for d + Au. 相似文献
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Wu Yuanfang Chen Lizhu Pan Xue Shao Ming Xiaosong Chen 《Central European Journal of Physics》2012,10(6):1341-1344
Accounting for the influence of system size in relativistic heavy ion collisions, the finite-size form of a critical related observable is suggested. The fixed-point and straight line methods are proposed in exploring the QCD critical point and phase boundary in relativistic heavy ion collisions. As an application, the finitesize behaviour of the ratios of higher net-proton cumulants, dynamical electric charge fluctuations, and transverse momentum correlations in Au + Au collisions at RHIC are examined. 相似文献