共查询到20条相似文献,搜索用时 15 毫秒
1.
Feng-Shou Zhang Lie-Wen Chen Wen-Fei Li Zhi-Yuan Zhu 《The European Physical Journal A - Hadrons and Nuclei》2000,9(2):149-152
The squeeze-out flow in reactions of 124Sn + 124Sn and 124Ba + 124Ba at different incident energies for different impact parameters is investigated by means of an isospin-dependent quantum
molecular dynamics model. For the first time, it is found that the more neutron-rich system (124Sn + 124Sn) exhibits weaker squeeze-out flow. This isospin dependence of the squeeze-out flow is shown to mainly result from the isospin
dependence of nucleon-nucleon cross-section and the symmetry energy.
Received: 14 March 2000 / Accepted: 29 September 2000 相似文献
2.
3.
D. Ghosh A. Deb M. Mondal S. Bhattacharyya J. Ghosh 《The European Physical Journal A - Hadrons and Nuclei》2002,14(1):77-80
Self-affine multiplicity scaling is investigated in the framework of two-dimensional factorial moment methodology using the
concept of the Hurst exponent (H). Our investigation on experimental data of the target-evaporated slow particles emitted in 32S-AgBr interactions at 200 AGeV and 28Si-AgBr interactions at 14.5 AGeV reveals that a better power law behavior is exhibited in self-affine analysis than self-similar
analysis. This work shows a clear evidence of self-affine target fragmentation.
Received: 22 October 2001 / Accepted: 6 March 2002 相似文献
4.
By evaluating all the contributions of the intermediate states of the multiple scattering theory diagrams, we compute the
integrated stripping cross sections of collisions among light nuclei. The resulting expressions have the simple form of a
combination of total inelastic cross sections of nuclear reactions with projectile nuclei differing in the atomic mass number.
We also check the accuracy of some widely used relations in heavy ion collisions.
Received: 18 March 1998 相似文献
5.
A. Andronic J. Łukasik W. Reisdorf W. Trautmann 《The European Physical Journal A - Hadrons and Nuclei》2006,30(1):31-46
Excitation functions of flow and stopping observables for the Au+ Au system at energies from 40 to 1500MeV per nucleon are
presented. The systematics were obtained by merging the results of the INDRA and FOPI experiments, both performed at the GSI
facility. The connection to the nuclear equation of state is discussed. 相似文献
6.
J. Brachmann A. Dumitru H. Stöcker W. Greiner 《The European Physical Journal A - Hadrons and Nuclei》2000,8(4):549-552
We investigate the excitation function of quark-gluon plasma formation and of directed in-plane flow of nucleons in the energy
range of the BNL-AGS and for the E
kin
Lab = 40A GeV Pb + Pb collisions performed recently at the CERN-SPS. We employ the three-fluid model with dynamical unification of
kinetically equilibrated fluid elements. Within our model with first-order phase transition at high density, droplets of QGP
coexisting with hadronic matter are produced already at BNL-AGS energies, E
kin
Lab≃ 10A GeV. A substantial decrease of the isentropic velocity of sound, however, requires higher energies, E
kin
Lab≃ 40A GeV. We show the effect on the flow of nucleons in the reaction plane. According to our model calculations, kinematic requirements
and EoS effects work hand-in-hand at E
kin
Lab = 40A GeV to allow the observation of the dropping velocity of sound via an increase of the directed flow around midrapidity as compared to top BNL-AGS energy.
Received: 7 May 2000 / Accepted: 2 August 2000 相似文献
7.
W. Nörenberg G. Papp P. Rozmej 《The European Physical Journal A - Hadrons and Nuclei》2000,9(3):327-343
The diabatic approach to dissipative collective nuclear motion is reformulated in the local-density approximation in order
to treat the normal modes of a spherical nuclear droplet analytically. In a first application the adiabatic isoscalar modes
are studied and results for the eigenvalues of compressional (bulk) and pure surface modes are presented as function of density
and temperature inside the droplet, as well as for different mass numbers and for soft and stiff equations of state. We find
that the region of bulk instabilities (spinodal regime) is substantially smaller for nuclear droplets than for infinite nuclear
matter. For small densities below 30% of normal nuclear matter density and for temperatures below 5 MeV all relevant bulk
modes become unstable with similar growth rates. The surface modes have a larger spinodal region, reaching out to densities
and temperatures way beyond the spinodal line for bulk instabilities. Essential experimental features of multifragmentation,
like fragmentation temperatures and fragment-mass distributions (in particular the power-law behavior) are consistent with
the instability properties of an expanding nuclear droplet, and hence with a dynamical fragmentation process within the spinodal
regime of bulk and surface modes (spinodal decomposition).
Received: 4 September 2000 / Accepted: 14 November 2000 相似文献
8.
K. Wi?niewski P. Crochet N. Herrmann A. Andronic R. Averbeck A. Devismes C. Finck A. Gobbi O. Hartmann K.D. Hildenbrand 《The European Physical Journal A - Hadrons and Nuclei》2000,9(4):515-519
The ratio of K- to K+-meson yields has been measured in the systems 96Ru + 96Ru at 1.69 A GeV, 96Ru+96Zr at 1.69 A GeV, and 58Ni+58Ni at 1.93 A GeV incident beam kinetic energy. The yield ratio is observed to vary across the measured phase space. Relativistic
transport-model calculations indicate that the data are best understood if in-medium modifications of the kaons are taken
into account.
Received: 30 November 1998 / Accepted: 20 December 2000 相似文献
9.
The double differential dilepton spectrum d/(d
2
d
⊥
2) at fixed transverse mass M
⊥ allows a direct access to the vector meson spectral functions. Within a fireball model the sensitivity of d/(d
2
d
⊥
2) against variations of both the in-medium properties of mesons and the dynamics of the fireball is investigated. In contrast
to the integrated invariant-mass spectrum d/d
2, in the spectrum d/(d
2
d
⊥
2) with fixed M
⊥ the ω signal is clearly seen as bump riding on the ρ background even in case of strong in-medium modifications.[3mm]
Received: 16 November 2000 / Accepted: 16 January 2001 相似文献
10.
K. A. Chikin V. L. Korotkih A. P. Kryukov L. I. Sarycheva I. A. Pshenichnov J. P. Bondorf I. N. Mishustin 《The European Physical Journal A - Hadrons and Nuclei》2000,8(4):537-548
There exist several proposals to use Weizsäcker-Williams photons generated by ultrarelativistic heavy ions to produce exotic particles in γγ fusion reactions. To estimate the background conditions for such reactions we analyze various mechanisms of meson production in very peripheral collisions of ultrarelativistic heavy ions at RHIC and LHC energies. Besides the γγ fusion they include also electromagnetic γA interactions and strong nucleon-nucleon interactions in grazing AA collisions. All these processes are characterised by low multiplicities of produced particles. The γA an d AA events are simulated by corresponding Monte Carlo codes, RELDIS and FRITIOF. In each of these processes a certain fraction of pions is produced close to the mid-rapidity regionthat gives a background for the γγ events. The possibility of selecting the mesons produced in the γγ fusion events via different p t cut procedures is demonstrated. 相似文献
11.
W. Nörenberg G. Papp P. Rozmej 《The European Physical Journal A - Hadrons and Nuclei》2002,14(1):43-51
Results on dissipative isoscalar modes of a hot and dilute nuclear droplet are presented. As compared to the adiabatic limit
(part I), realistic dissipation yields a substantial reduction of the growth rates for all unstable modes, while the area
of spinodal instability in the (ϱ,T)-plane remains unchanged. The qualitative features of multifragmentation through spinodal decomposition as obtained in the
adiabatic limit are not significantly affected by dissipation.
Received: 10 January 2002 / Accepted: 10 February 2002 相似文献
12.
C. Beşliu A. Jipa D. Argintaru C. Argintaru R. Zaharia J. Gabriel Rican M. Iosif 《The European Physical Journal A - Hadrons and Nuclei》1998,1(1):65-75
The problem of the nuclear matter jets in nucleus-nucleus collisions at 4.5 A GeV/c is discussed. The global analysis of
experimental data, namely the sphericity tensor, is used to evidence such jets. The experimental results are compared with
those obtained in the same collisions for hydrodynamic flow and thrust. The experiments have been performed in the frame of
the SKM 200 Collaboration from JINR Dubna.
Received: 20 March 1997 / Revised version: 20 July 1997 相似文献
13.
Identification of baryon resonances in central heavy-ion collisions at energies between 1 and 2 AGeV
《The European Physical Journal A - Hadrons and Nuclei》1998,3(4):335-349
The mass distributions of baryon resonances populated in near-central collisions of Au on Au and Ni on Ni are deduced by
defolding the pt spectra of charged pions by a method which does not depend on a specific resonance shape. In addition the mass distributions
of resonances are obtained from the invariant masses of (p, π±) pairs. With both methods the deduced mass distributions are shifted by an average value of −60 MeV/c2 relative to the mass distribution of the free Δ(1232) resonance, the distributions descent almost exponentially towards mass
values of 2000 MeV/c2. The observed differences between (p, π−) and (p, π+) pairs indicate a contribution of isospin I = 1/2 resonances. The attempt to consistently describe the deduced mass distributions
and the reconstructed kinetic energy spectra of the resonances leads to new insights about the freeze out conditions, i.e.
to rather low temperatures and large expansion velocities.
Received: 26 June 1998 / Revised version: 2 September 1998 相似文献
14.
We have studied the properties of the relativistic helium fragments emitted from the projectile in the interactions of 24Mg ions accelerated at an energy of 3.7 A GeV with emulsion nuclei. The total, partial nuclear cross-sections and production rates of helium fragmentation channels in relativistic nucleus-nucleus collisions and their dependence on the mass and energy of the incident projectile nucleus are investigated. The yields of multiple helium projectile fragments disrupted from the interactions of 24Mg projectile nuclei with hydrogen H, light CNO and heavy AgBr groups of target emulsion nuclei are discussed and they indicate that the breakup mechanism of the projectile seems to be independent of the target mass. Limiting fragmentation behavior of fast-moving helium fragments is observed in both the projectile and target nuclei. The multiplicity distributions of helium projectile fragments emitted in the interactions of 24Mg projectile nuclei with the different target nuclei of the emulsion are well described by the KNO scaling presentation. The mean multiplicities of the different charged secondary particles, normally defined shower, grey and black ( ns, ng and nb) emitted in the interactions of 3.7 A GeV 24Mg with the different groups of emulsion nuclei at different ranges of projectile fragments are decreasing when the number of He fragments stripped from projectile increases. These values of ni ( i = s, g, b and h particles) in the events where the emission of fast helium fragments were accompanied by heavy fragments having Z 3 seem to be constant as the He multiplicity increases, and exhibit a behavior independent of the He multiplicity. 相似文献
15.
R. Andrade F. Grassi Y. Hama T. Kodama O. Socolowski jr. B. Tavares 《The European Physical Journal A - Hadrons and Nuclei》2006,29(1):23-26
Elliptic flow at RHIC is computed event by event with NeXSPheRIO. Reasonable agreement with experimental results on v
2(η) is obtained. Various effects are studied as well: reconstruction of impact parameter direction, freeze-out temperature,
equation of state (with or without crossover), emission mechanism. 相似文献
16.
17.
B. Kämpfer O.P. Pavlenko S. Zschocke 《The European Physical Journal A - Hadrons and Nuclei》2003,17(1):83-87
QCD sum rules predict that the change of the strange quark condensate 〈ˉss〉 in hadron matter at finite baryon density causes a shift of the peak position of the di-electron spectra from φ-meson decays.
Due to the expansion of hadron matter in heavy-ion collisions, the φ peak suffers a smearing governed by the interval of density
in the expanding fireball, which appears as an effective broadening of the di-electron spectrum in the φ region. The emerging
broadening is sensitive to the in-medium change of 〈ˉss〉. This allows to probe directly in-medium modifications of 〈ˉss〉 via di-electron spectra in heavy-ion collisions at SIS energies with HADES.
Received: 22 November 2002 / Accepted: 30 January 2003 / Published online: 29 April 2003 相似文献
18.
19.
M. B. Tsang R. Bougault R. Charity D. Durand W. A. Friedman F. Gulminelli A. Le Fèvre Al. H. Raduta Ad. R. Raduta S. Souza W. Trautmann R. Wada 《The European Physical Journal A - Hadrons and Nuclei》2006,30(1):129-139
The results from ten statistical multifragmentation models have been compared with each other using selected experimental
observables. Even though details in any single observable may differ, the general trends among models are similar. Thus, these
models and similar ones are very good in providing important physics insights especially for general properties of the primary
fragments and the multifragmentation process. Mean values and ratios of observables are also less sensitive to individual
differences in the models. In addition to multifragmentation models, we have compared results from five commonly used evaporation
codes. The fluctuations in isotope yield ratios are found to be a good indicator to evaluate the sequential decay implementation
in the code. The systems and the observables studied here can be used as benchmarks for the development of statistical multifragmentation
models and evaporation codes.
An erratum to this article is available at . 相似文献
20.
A formalism for anisotropic fluid dynamics is proposed. It is designed to describe boost-invariant systems with anisotropic pressure. Such systems are expected to be produced at the early stages of relativistic heavy-ion collisions, when the timescales are too short to achieve equal thermalization of transverse and longitudinal degrees of freedom. The approach is based on the energy–momentum and entropy conservation laws, and may be regarded as a minimal extension of the boost-invariant standard relativistic hydrodynamics of the perfect fluid. We show how the formalism may be used to describe the isotropization of the system (the transition from the initial state with no longitudinal pressure to the final state with equal longitudinal and transverse pressure). 相似文献