共查询到20条相似文献,搜索用时 31 毫秒
1.
WANG Yang-Yang ZHAO Lin-Jie YUAN Zhong-Sheng ZHANG Dan-Dan FANG Wei XU Ming-Mei 《中国物理C(英文版)》2011,35(3)
System size is more than a geometrical quantity in relativistic heavy ion collisions; it is closely related to evolution process,i.e.a different system size corresponds to a different evolution process,and whether QGP is produced depends on the system size.We propose that the system size should be under the same level when comparing the measurements from different colliding nuclei.The equivalence of the peripheral collisions of Au-Au and the central collisions of smaller nuclei is studied using the Monte Carlo method.Comparing the transverse overlapping area of the colliding nuclei,the number of participant nucleons and the number of nucleon-nucleon binary collisions in various colliding nuclei,we give an estimate of the correspondence in system size.This is helpful in the experimental comparison of the measurements from different colliding nuclei. 相似文献
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V. V. Volkov E. A. Cherepanov Sh. A. Kalandarov 《Physics of Particles and Nuclei Letters》2016,13(6):729-736
The new approach to the interpretation of the process of spontaneous fission of heavy nuclei is suggested. It is based on nuclear physics data which are obtained in heavy ion collisions. The process of spontaneous fission consists of three sequential stages: clusterization of the valent nucleons of a heavy nucleus into a light nucleus-cluster, which leads to the formation of a dinuclear system; evolution of the dinuclear system which proceeds by nucleon transfer from the heavy to light nucleus and decay of the dinuclear system from the equilibrium configuration into two fragments. 相似文献
3.
V. I. Zagrebaev V. V. Samarin 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(3):386-392
The evolution of the wave functions of valence neutrons upon collisions of heavy nuclei having energies near the Coulomb barrier has been investigated by numerical solution of the multidimensional time-dependent Schrödinger equation. It is shown that even before overcoming the barrier by nuclei the wave functions of valence neutrons are extended to their volumes with occupation of quasi-molecular states. This process results in a significant effect of neutron transfers on nuclear fusion and, in particular, in a significant increase in the probability of subbarrier fusion for certain combinations of nuclei. 相似文献
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Peter Seyboth 《Acta Physica Hungarica A》2002,15(3-4):257-268
Experiment NA49 at the Cern SPS has performed large acceptance measurements of hadron production in pp, pPb, CC, SiSi and PbPb collisions at 40 and 158 A·GeV beam energies. These data allowed a study of particle yields, spectra and correlations as well as event-by-event fluctuations of average event properties of the created hadron system. Results from central PbPb collisions are consistent with the onset of deconfinement during the early stage of the reaction in the lower SPS energy range. A new scaling property of particle production ratios was found which relates collision systems of different size and centrality. Systematics of the evolution of particle production from pp via pPb to PbPb collisions were investigated. 相似文献
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A. B. Kurepin 《Physics of Atomic Nuclei》2002,65(2):325-328
An anomalous suppression of the charmonium yield in central collisions was observed in studying charmonium production in collisions of Pb nuclei accelerated to a momentum of 158 GeV/c per nucleon with Pb target nuclei. It is shown that, in peripheral collisions, the ratio of the cross section for J/ψ production to the cross section for the Drell-Yan process decreases exponentially (as in the case of collisions of lighter nuclei) owing to the ordinary absorption of J/gy in nuclear matter. The observed threshold effect of the anomalous suppression of charmonium production agrees well with the predictions based on the assumption of Debye color screening in the formation of quark-gluon plasma. 相似文献
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采用分子动力学方法对液态金属钾凝固过程进行了模拟,根据凝固过程体系平均原子能量、原子成键类型和成团类型,以及均方位移和非Gauss参数等动力学参数的演化特征,对过冷熔体形核初期微观动力学机理进行了研究.结果表明:根据过冷液体钾结晶形核过程热力学、动力学和结构特性的演化规律, 其过冷温度区间可以分为两个明显不同的阶段,潜在结晶核心出现在过冷液体较低温区.过冷熔体钾在形核初期,二十面体团簇结构在α-弛豫阶段逐渐解体,同时具有体心立方(bcc)结构的潜在结晶核心逐步形成,其临界晶核包含约300个原子. 相似文献
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V. V. Volkov 《Physics of Atomic Nuclei》2007,70(12):2046-2053
The centrifugal fragmentation of a dinuclear system in the process of evolution toward a compound nucleus is examined. If the angular momentum in the collision of primary nuclei is quite high, centrifugal forces become dominant at the final stage of the evolution of the dinuclear system formed, causing the decay of this dinuclear system to two strongly asymmetric nuclear fragments. Experimental data in which this specific nuclear process manifests itself are presented. Centrifugal fragmentation makes it possible to reveal the cluster facet of the evolution of a dinuclear system toward a compound nucleus. The possibility of this fragmentation process is a logical consequence of the concept of a dinuclear system for the complete fusion of nuclei. 相似文献
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A new process of a nuclear excitation to discrete states in peripheral heavy ion collisions is studied. High-energy photons
are emitted by the exited nuclei with energies up to a few tens of GeV at angles of a few hundred microradians with respect
to the beam direction. We show that a two-stage process, where an electron-positron pair is produced by virtual photons emitted
by nuclei and then the electron or positron excites the nucleus, has a large cross-section. It is equal to about 5 b for CaCa
collisions. On the one hand, it produces a significant γ-rays background in the nuclear fragmentation region but, on the other
hand, it could be used for monitoring the nuclear beam intensity at the LHC. These secondary nuclear photons could be a good
signal for triggering peripheral nuclear collisions.
Received: 14 December 2001 / Accepted: 22 January 2002 相似文献
12.
J. Sollfrank P. Huovinen P. V. Ruuskanen 《The European Physical Journal C - Particles and Fields》1999,6(3):525-536
We study the different nucleus-nucleus collisions, O+Au, S+S, S+Ag, S+Au and Pb+Pb, at the CERN-SPS energy in a one-fluid
hydrodynamical approach using a parametrization based on baryon stopping in terms of the thickness of colliding nuclei. Good
agreement with measured particle spectra is achieved. We deduce the mass number scaling behaviour of the initial energy density.
We find that the equilibration time is nearly independent of the size of the colliding nuclei.
Received: 23 January 1998 / Revised version: 8 May 1998 / Published online: 12 August 1998 相似文献
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No conventional picture of nucleus-nucleus collisions has yet been able to explain the abundance of Omega and Omega; hadrons in central collisions between Pb nuclei at 158A GeV at the CERN SPS. We argue that this is evidence that they are produced as topological defects arising from the formation of disoriented chiral condensates with an average domain size of about 2 fm. 相似文献
15.
U. Müller G. Soff T. de Reus J. Reinhardt B. Müller W. Greiner 《Zeitschrift für Physik A Hadrons and Nuclei》1983,313(4):263-279
During collisions of heavy nuclei with a combined chargeZ?160 the electronic 1s-state is deeply bound due to the strong Coulomb field, forZ≧173 it even enters as a resonance the lower continuum of the Dirac-Hamiltonian. In pure Rutherford scattering no qualitative indication for the filling of a dynamically createdK-hole by the spontaneous positron creation process is predicted, but the study of heavy-ion collisions with nuclear time delay due to the attractive nuclear force promises clear signatures for the decay of the vacuum. Emphasis is laid also on the quantitative influence of the electron-electron interaction and ofE0-transitions in the giant nuclear system on positron emission, the latter treated in a classical approximation. We compare our results with recent experimental data of two different groups at GSI, Darmstadt. 相似文献
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M. El-Nadi A. Abdelsai.am A. Hussien E. A. Shaat N. Ali Moussa Z. Abou Moussa S. Kamel Kh. Abdel-Waged E. El Falaky M. Fayed 《Radiation measurements》1997,28(1-6):231-240
Data on fragmentation of 32S nuclei in emulsion at 3.7 AGeV are presented. The fragmentations are studied in terms of the impact parameter of collisions of the 32S projectiles with the different target nuclei. The fragmentation cross sections and the multiplicities of the different fragments are nearly independent of the sulfur incident energy. The fragmentation of 32S nuclei into alpha isotopes are extensively studied. The transverse momentum spectra of the emitted fragments are fitted by two Maxwell-Boltzmann distributions of different average transverse momenta. The characteristics (multiplicities and Pt-distributions) of the He-fragments produced in the central collisions are different from those emitted in the peripheral collisions. 相似文献
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M. S. Borysova Iu. A. Karpenko Yu. M. Sinyukov 《Physics of Particles and Nuclei Letters》2011,8(9):915-917
Two-particle angular correlation for charged particles emitted in Au + Au collisions at the center-of-mass of 200 MeV measured at RHIC energies revealed novel structures commonly referred to as a nearside ridge. The ridge phenomenon in relativistic A + A collisions is rooted probably in the initial conditions of the thermal evolution of the system. In this study we analyze the evolution of the bumping transverse structure of the energy density distribution caused by fluctuations of the initial density distributions that could lead to the ridge structures. We suppose that at very initial stage of collisions the typical one-event structure of the initial energy density profile can be presented as the set of longitudinal tubes, which are boost invariant in some space-rapidity region and are rather thin. These tubes have very high energy density comparing to smooth background density distribution. The transverse velocity and energy density profiles at different times of the evolution till the chemical freeze-out (at the temperature T = 165 MeV) will be reached by the system are calculated for sundry initial scenarios. 相似文献
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The nucleon exchange process between two nuclei in close proximity and its application to an explanation of fragment mass
and charge distributions in fission and in heavy ion deep inelastic collisions are reviewed. An analysis of the measured correlations
between the energy loss from relative motion and the fragment mass and charge variances in the heavy ion deep inelastic collisions
is presented. The recent data on fragment mass and charge variances as a function of the fragment kinetic energy in thermal
neutron induced fission of235U, lends added support to the hypothesis that the nucleon transport process plays a similar role both in fission and in heavy
ion deep inelastic collisions. 相似文献