共查询到20条相似文献,搜索用时 156 毫秒
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双轻子是研究夸克物质的形成和性质的重要探针.本文基于化学平衡化的黏滞性夸克胶子等离子体演化模型,计算了相对论重离子碰撞能量下金-金对心碰撞形成的夸克胶子等离子体中的双轻子产额.在黏滞性计算中加入了胶子非弹性散射过程对黏滞系数的贡献.相较仅考虑夸克和胶子弹性散射的情况,双轻子的产额有较明显的降低.这表明在黏滞系数中加入胶子非弹性散射的贡献使得系统的演化过程加快,演化时间变短. 相似文献
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基于一个描述夸克胶子火柱演化的相对论流体力学模型,研究了夸克相、强子相互作用以及非热过程(DrellYan对、粲强子衰变)的中等质量双轻子的产生.发现由于相边对夸克胶子物质演化的影响和RHIC能量核碰撞产生的夸克胶子物质具有高的初始温度,夸克相对双轻子的贡献显著增强,比那些来自强子相互作用的贡献重要,甚至能与来自非热的贡献比较.表明中等质量双轻子的增强是一个在核碰撞中产生了夸克胶子物质的可能信号.
关键词:
夸克-胶子物质
双轻子增强
相对论流体力学模型 相似文献
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从动力论理论出发,使用弱湍理论方法,有效地展开了夸克–胶子等离子体的动力论方程,从而给出了夸克–胶子等离子体介质对外流的非线性非阿贝尔响应方程。 相似文献
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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. 相似文献
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建立了夸克胶子等离子体中胶子的经典输运方程, 并讨论了它与胶子的量子输运方程以及它与夸克的经典输运方程之间的关系. 相似文献
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The production of dileptons in the intermediate mass region in QGP has been studied on the basis of a relativistic hydrodynamic model. Due to the influence of the phase boundary on the evolution of the QGP system and the high initial temperature of the QGP produced at RHIC energies, the quark phase contribution is much more important than that from hadronic interactions and even comparable with that from background sources. It is shown that such an enhancement is a signature for the QGP formation. 相似文献
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The photon yield from a baryon-rich quark gluon plasma (QGP) at SPS energy has been estimated. In the QGP phase, rate of photon
production is evaluated up to two-loop level. In the hadron phase, dominant contribution from π,ρ, ω mesons has been considered. The evolution of the plasma has been studied with appropriate equation of state in both QGP
and hadron phase for a baryon-rich system. At SPS energy, the total photon yield is found to increase marginally in the presence
of baryon density. 相似文献
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The thermodynamic properties of the quark-gluon plasma (QGP), as well as its phase diagram, are calculated as a function of baryon density (chemical potential) and temperature. The QGP is assumed to be composed of the light quarks only, i.e., the up and down quarks, which interact weakly, and the gluons which are treated as they are free. The interaction between quarks is considered in the framework of the one gluon exchange model which is obtained from the Fermi liquid picture. The bag model is used, with fixed bag pressure (B)for the nonperturbative part, and the quantum chromodynamics (QCD) coupling is assumed to be constant, i.e., with no dependence on the temperature or the baryon density. The effect of weakly interacting quarks on the QGP phase diagram are shown and discussed. It is demonstrated that the one-gluon exchange interaction for the massless quarks has considerable effect on the QGP phase diagram and it causes the system to reach to the confined phase at the smaller baryon densities and temperatures. The pressure of excluded volume hadron gas model is also used to find the transition phase diagram. Our results depend on the values of bag pressure and the QCD coupling constant. The latter does not have a dramatic effect on our calculations. Finally, we compare our results with the thermodynamic properties of strange quark matter and the lattice QCD prediction for the QGP transition critical temperature. 相似文献
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基于相对论流体力学,指出了新近报道的首次实测的纯光子谱虽然具有线性,但并不意味着极端相对论性原子核碰撞后的系统在整体上达到了热平衡. 运用动态相变机制的计算结果可以预言,若强子化相变是一级相变,当碰撞能量高于200GeV/u时,纯光子谱将呈现凹形曲线,可以用作诊断夸克-胶子等离子体是否存在的信号. 相似文献
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Saeed-uddin 《The European Physical Journal C - Particles and Fields》1999,6(2):355-363
The implications of the strangeness conservation in a hadronic resonance gas (HRG) on the expected phase transition to the
quark gluon plasma (QGP) are investigated. It is assumed that under favourable conditions a first order hadron-quark matter
phase transition may occur in the hot hadronic matter such as those produced in the ultra-relativistic heavy-ion collisions
at CERN and BNL. It is however shown that the criteria of strict strangeness conservation in the HRG may not permit the occurrence
of a strict first order equilibrium quark-hadron phase transition unlike a previous study. This emerges as a consequence of
the application of a realistic equation of state (EOS) for the HRG and QGP phases, which account for the finite-size effect
arising from the short range hard-core hadronic repulsion in the HRG phase and the perturbative QCD interactions in the QGP
phase. For a first order hadron-quark matter phase transition to occur one will therefore require large fluctuations in the
critical thermal parameters, which might arise due to superheating, supercooling or other nonequlibrium effects. We also discuss
a scenario proposed earlier, leading to a possible strangeness separation process during hadronization.
Received: 25 August 1997 / Revised version: 25 March 1998 / Published online: 26 August 1998 相似文献
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We calculate the Gaussian radius parameters of the pion-emitting source in high-energy heavy-ion collisions, assuming a first-order phase transition from a thermalized quark-gluon plasma (QGP) to a gas of hadrons. Such a model leads to a very long-lived dissipative hadronic rescattering phase which dominates the properties of the two-pion correlation functions. The radii are found to depend only weakly on the thermalization time tau(i), the critical temperature Tc (and thus the latent heat), and the specific entropy of the QGP. The model calculations suggest a rapid increase of R(out)/R(side) as a function of KT if a thermalized QGP were formed. 相似文献
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B. K. Srivastava 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):862-867
The study of correlations and fluctuations can provide evidence for the production of the quark-gluon plasma (QGP) in relativistic
heavy-ion collisions. Various theories predict that the production of a QGP phase in relativistic heavy-ion collisions could
produce significant event-by-event correlations and fluctuations in transverse momentum, multiplicity, etc. Some of the recent
results using STAR at RHIC will be presented along with results from other experiments at RHIC. The focus is on forward-backward
multiplicity correlations, balance function, charge and transverse-momentum fluctuations, and correlations. 相似文献
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《Nuclear Physics A》1997,624(4):738-754
Hadrons emitted by the pre-surface layer of a quark-gluon plasma (QGP) before the phase transition into a hadronic gas are considered as possible sources of direct information about QGP. It is shown that if QGP is created in ultrarelativistic heavy-ion collisions, then these hadrons strongly contribute at soft pt at SpS energy and dominate up to an order of magnitude at LHC energy. 相似文献
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K. A. Bugaev 《Physics of Particles and Nuclei Letters》2011,8(9):907-911
On the basis of exactly solvable models with the tricritical and critical endpoints I discuss the physical mechanism of endpoints
formation which is similar to the usual liquids. It is demonstrated that the necessary condition for the transformation of
the 1-st order deconfinement phase transition into the 2-nd order phase transition at the (tri)critical endpoint is the vanishing
of surface tension coefficient of large/heavy QGP bags. Using the novel model of the confinement phenomenon I argue that the
physical reason for the cross-over appearance at low baryonic densities is the negative value of QGP bag surface tension coefficient.
This implies the existence of highly non-spherical or, probably, even fractal surfaces of large and heavy bags at and above
the cross-over, which, perhaps, can be observed via some correlations. The model with the tricritical endpoint predicts that
at the deconfinement transition line the volume (mass) distribution of large (heavy) QGP bags acquires the power law form
at the endpoint only, while in the model with the critical endpoint such a power law exists inside the mixed phase. The role
of finite width of QGP bags is also discussed. 相似文献
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The recent status of hard thermal photon production in relativistic heavy ion collisions is reviewed and the current rates are presented with emphasis on corrected bremsstrahlung processes in the quark–gluon plasma (QGP) and quark–hadron duality. Employing Bjorken hydrodynamics with an EOS supporting the phase transition from QGP to hot hadron gas (HHG), thermal photon spectra are computed. For SPS 158 GeV Pb + Pb collisions, comparison with other theoretical results and the WA98 direct photon data indicates significant contributions due to prompt photons. Extrapolating the presented approach to RHIC and LHC experiments, predictions of the thermal photon spectrum show a QGP outshining the HHG in the high-pT-region. 相似文献