共查询到20条相似文献,搜索用时 0 毫秒
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基于Nambu-Jona-Lasinio(NJL)模型讨论了有限温度、有限密度下的强子化过程,考虑夸克-反夸克对转换成两个介子的情形,其微分散射截面作为质心系能量s,温度T和化学势的函数被计算到1/Nc展开的第一阶.着重考察有限密度情形手征对称性对强子化过程的影响. 相似文献
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We discuss how the dynamics of an exploding hot fireball of quark-gluon matter impacts the actual phase transition conditions
between the deconfined and confined state of matter. We survey the chemical conditions prevailing at hadronization. 相似文献
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The transverse momentum spectra for identified hadrons at different rapidities in central Au+Au collisions at = 200 GeV are studied in a quark combination model. The results for PT spectra of π±,K±, p(p-) and for the p/π ratios in a broader PT range at midrapidity agree well with the data. The transverse momentum spectra of pions, protons and antiprotons at various rapidities y 1, η= 2.2 and y≈3.2 are calculated and compared with the data. 相似文献
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The transverse momentum spectra for identified hadrons at different rapidities in central Au+Au collisions at √^SNN= 200 GeV are studied in a quark combination model. The results for PT spectra of π^±, K^±, p(p^-) and for the p/π ratios in a broader PT range at midrapidity agree well with the data. The transverse momentum spectra of pions, protons and antiprotons at various rapidities y - 1, η= 2.2 and y ≈ 3.2 are calculated and compared with the data. 相似文献
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The clustering of sulphuric acid with base molecules is one of the main pathways of new-particle formation in the Earth's atmosphere. First step in the clustering process is likely the formation of a (sulphuric acid)1(base)1(water)n cluster. Here, we present results from direct first-principles molecular dynamics collision simulations of (sulphuric acid)1(water)0, 1 + (dimethylamine) → (sulphuric acid)1(dimethylamine)1(water)0, 1 cluster formation processes. The simulations indicate that the sticking factor in the collisions is unity: the interaction between the molecules is strong enough to overcome the possible initial non-optimal collision orientations. No post-collisional cluster break up is observed. The reasons for the efficient clustering are (i) the proton transfer reaction which takes place in each of the collision simulations and (ii) the subsequent competition over the proton control. As a consequence, the clusters show very dynamic ion pair structure, which differs from both the static structure optimisation calculations and the equilibrium first-principles molecular dynamics simulations. In some of the simulation runs, water mediates the proton transfer by acting as a proton bridge. In general, water is able to notably stabilise the formed clusters by allocating a fraction of the released clustering energy. 相似文献
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钠原子团簇的碰撞动力学 总被引:1,自引:1,他引:0
采用紧密结合的分子动力学模型,对第一个满壳附近(n=8)钠原子团簇碰撞Nan+Nan的动力学性质进行了系统性研究。对有限温度下的多次模拟事件,在各种碰撞参数与不同轰击能量时,双团簇(Nan)2的稳定性进行了研究。并发现,当质心系单原子能量为0.025eV时,对中心碰撞,(Na8)2能够存在3000fs,而对周边碰撞,(Na8)2能够存在10000fs;不管对中心碰撞还是对周边碰撞,在较低的轰击能量下,这种暂态双团簇结构具有较长的寿命;在相同的单原子轰击能量和相同的碰撞参数,(Na8)2和(Na9)2的动力学寿命没有差别,只是(Na8)2比(Na9)2的温度更低。 相似文献
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采用距离相关紧束缚的分子动力学模型 ,在不同初始温度T0 =0 .0 2K、50K、10 0K、2 0 0K、30 0K、4 0 0K时 ,对Na8 Na8在质心系轰击能量为 0 .0 12 5eV/n的中心碰撞时的反应动力学进行了研究。发现团簇碰撞动力学与初始温度密切相关。在T0 <10 0K时 ,初始温度不影响反应动力学 ,而在T0 =4 0 0K时将对反应动力学有强烈影响。 相似文献
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We propose a forward method based on PYTHIA6.4 to study the jet properties in ultra-relativistic pp collisions.In the forward method,the partonic initial states are first generated with PYTHIA6.4 and then hadronized in the Lund string fragmentation model,and finally the hadronic jets are constructed from the created hadrons.Jet properties calculated with the forward method for pp collisions at √s=7 TeV are comparable to those calculated with the usual anti-kt algorithm(backward method)in PYTHIA6.4.The comparison between the backward and forward methods may contribute to the understanding of the partonic origin of jets in the backward method. 相似文献
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Perturbative unitarization from non-linear effects is thought to deplete the gluon density for transverse momenta below the saturation scale. Such effects also modify the distribution of gluons produced in heavy-ion collisions in transverse impact parameter space. I discuss some of the consequences for the initial conditions for hydrodynamic models of heavy-ion collisions and for hard “tomographic” probes. Also, I stress the importance of realistic modelling of the fluctuations of the valence sources for the small-x fields in the impact parameter plane. Such models can now be combined with solutions of running–coupling Balitsky–Kovchegov evolution to obtain controlled predictions for initial conditions at the LHC. 相似文献
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D S Narayan 《Pramana》1974,2(5):252-258
Topological cross sections for diffractive and nondiffractive components in pp collisions are deduced on the basis of a dynamical
model proposed earlier to explain the multiplicity distribution of charged particles. The model has an important prediction
for the angular and momentum distributions of charged particles in diffractive events. 相似文献
13.
Mingrui Wei Sheng Wu Fan Li Dongju Zhang Tingting Zhang 《Combustion Theory and Modelling》2017,21(6):1189-1198
Pyrene dimerisation was successfully used to model the beginning of soot nucleation in some simulation models. However, the quantum mechanics (QM) calculations proved that the binding energy of a PAH dimer with three six-member rings was similar to that of a pyrene dimer. Meanwhile, the high concentration of phenanthrene at flame conditions indicated high probability of collisions among them. The small difference of the binding energy and high concentration indicated that PAHs structurally smaller than pyrene also could be involved in soot inception. Hence, binary collisions of phenanthrene were simulated to find out whether phenanthrene dimers can serve as soot primary nuclei or not by using non-equilibrium molecular dynamics (MD). Three temperatures, six collision orientations and 155 initial translational velocities (ITVs) were considered. The results indicated that the number of dimers with lifetime over 10 ps which can serve as soot nuclei decreased from 52 at 1000 K to 17 at 1600 K, and further to 6 at 2400 K, which means that low temperature was more favourable for phenanthrene to form soot nuclei. Meanwhile, no soot nuclei were formed at the high velocity region (HVR), compared to 43 and 9 at low and middle velocity regions (LVR and MVR), respectively, when temperature was 1000 K. Also, no soot nuclei were formed at HVR when the temperature was raised to 1600 K and 2400 K. This indicated that HVR was unfavourable for phenanthrene to form soot nuclei. The results computationally further illustrated that small PAHs such as phenanthrene could serve as soot primary nuclei, since they have similar mole fractions in some flames. This may be useful for future soot simulation models. 相似文献
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In the past two decades, the revolutionary technologies of creating cold and ultracold molecules have provided cutting-edge experiments for studying the fundamental phenomena of collision physics. To a large degree, the recent explosion of interest in the molecular collisions has been sparked by dramatic progress of experimental capabilities and theoretical methods, which permit molecular collisions to be explored deep in the quantum mechanical limit. Tremendous experimental advances in the field have already been achieved, and the authors, from an experimental perspective, provide a review of these studies for exploring the nature of molecular collisions occurring at temperatures ranging from the Kelvin to the nanoKelvin regime, as well as for applications of producing ultracold molecules. 相似文献
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We analyze the formation of fragments in O—Br reaction at different incident energies between E/A=50 MeV and 200 MeV. This study is carried out within the quantum molecular dynamics (QMD) model coupled with recently advanced
simulated annealing clusterization algorithm (SACA). For comparison, we also use the conventional minimum spanning tree (MST)
method. Our detailed study shows that the SACA can detect the final stable fragment configuration as early as 60 fin/c which
is marked by a dip in the heaviest fragment. On the other hand, the MST method needs several hundred fm/c to identify the
final stable distribution. A comparison of the charge distribution with experimental data shows that the SACA is able to reproduce
the data very nicely whereas (as reported earlier) the MST method fails to break the spectator matter into intermediate mass
fragments. Furthermore, our results with SACA method indicate the onset of multi-fragmentation around 75 MeV/A which is again
in good agreement with experimental findings. 相似文献
16.
R.C. Bernardi D.E.B. Gomes R. Gobato A.T. Ota P.G. Pascutti 《Molecular physics》2013,111(14):1437-1443
It is still controversial how local anesthetics (LAs) act upon the nervous system and how the membrane contributes to this process, since probably the most important active site of the LAs is located in the sodium channels, a trans-membrane protein. An important role of the bio-membrane would be the stabilization and orientation of local anesthetics molecules, reducing their translational and rotational degrees of freedom, which could reinforce the mechanisms which interrupt the nervous impulse. This study aims to perform a computational analysis of the LAs behaviour in the membrane, and the effect of the water/membrane interface on their stabilization and orientation. Analysis by molecular dynamics (MD) showed that the charged form of these drugs are oriented at the interface, while the neutral form can easily cross the interface, entering the membrane, in agreement with the most recent experimental results in the literature. In contrast, it is here suggested that benzocaine (BZC), which exists only in its uncharged form in physiological media, behaves like the charged anesthetics, remaining stabilized and oriented at the interface. This could explain the similar anesthetic effect of BZC and the charged forms of tetracaine (TTC) and lidocaine (LDC). 相似文献
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We present an analytic study of the physics of the glasma which is a strong classical gluon field created at early stage of high-energy heavy-ion collisions. Our analysis is based on the picture that the glasma just after the collision is made of color electric and magnetic flux tubes extending in the longitudinal direction with their diameters of the order of 1/Qs (Qs is the saturation scale of the colliding nuclei). We find that both the electric and magnetic flux tubes expand outwards and the field strength inside the flux tube decays rapidly in time. Next we investigate whether there exist instabilities against small rapidity-dependent perturbations for a fixed color configuration. We find that the magnetic background field exhibits an instability induced by the fluctuations in the lowest Landau level, and it grows exponentially in the time scale of 1/Qs. For the electric background field we find no apparent instability while the possible relation to the Schwinger mechanism for particle pair creations is suggested. 相似文献
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The properties of the relativistic helium fragments produced in interactions of 84 Kr at 1.8 A GeV and 197 Au at 10.7 A GeV in emulsion are investigated. The experimental results are compared with those obtained from various projectiles with emulsion collisions at different energies. It is found that the multiplicity distribution of helium projectile fragments (HPFs) is well described by the Koba-Nielsen-Olesen (KNO) scaling presentation. The second Mueller moment f 2 of the HPF multiplicity distribution is independent of the projectile energy for the same projectile, but it is dependent on the projectile mass number. The value of f 2 increases with the increase of projectile mass number A p . The negative value of f 2 , when A p < 69, means that the emission of HPFs is anticorrelated, but positive value of f 2 , when A p > 69, refers to that the emission of HPFs is correlated. The non-zero f 2 moment in this experiment implies the strong correlation existing between the HPFs. 相似文献
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团簇碰撞中双团簇分子(Na_9)_2的形成研究 总被引:1,自引:1,他引:0
采用紧密结合分子动力学模型 ,对Na9+Na9碰撞系统在质心系中单原子的轰击能量为Ecm/n =0 .0 0 63eV的对心碰撞进行了研究。从动力学的观点对双团簇分子 (Na9) 2 的形成给予了证明 ,结合所谓“突然冷却”技术 ,鉴别出了所形成的 (Na9) 2 ,并给出了其结构性质。 相似文献
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Federico Nguyen 《中国物理 C》2010,34(6):795-800
Studies of γγ interactions are performed with the KLOE detector, without tagging of the outgoing e^+e^-. The data sample is from an integrated luminosity of 240 pb^-1. It was collected at the φ-factory DAONE with e^+e^- beams colliding at √s ≌1 GeV, below the φ resonance peak. We present preliminary results concerning the observation of the γγ→η process and the evidence for γγ→π^0π^0 production at low π^0π^0 invariant masses. 相似文献