共查询到20条相似文献,搜索用时 15 毫秒
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《Nuclear Physics A》1988,487(1):175-194
Heavy-ion fusion and deep inelastic reactions have been studied for symmetric systems in a classical dynamical model with deformation and necking as the collective shape coordinates. The calculated fusion excitation functions (for compound nucleus formation) are in good agreement with the experimental results from the evaporation residue measurements. It is observed that “nuclear molecules” are formed for not too heavy systems. The calculated reaction time for collisions of very heavy ions like 238U + 238U is found to be ~10−21 sec only and thus the width of the positron spectra observed in these reactions can not be explained in the light of quantum electrodynamics. The extra-extra push energies for fusion of heavy nuclei have also been studied. 相似文献
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Abbott T Akiba Y Beavis D Bloomer MA Bond PD Chasman C Chen Z Chu YY Cole BA Costales JB Crawford HJ Cumming JB Debbe R Duek E Engelage J Fung SY Gushue S Hamagaki H Hansen O Hayano RS Hayashi S Haustein PE Homma S Huang HZ Ikeda Y Juricic I Kang J Katcoff S Kaufman S Kimura K Kitamura K Kurita K Ledoux RJ LeVine MJ Miake Y Morse RJ Moskowitz B Nagamiya S Olness J Parsons CG Remsberg LP Sakurai H Sarabura M Stankus P Steadman SG Stephans GS Sugitate T Tannenbaum MJ van Dijk JH Videbaek F 《Physical review letters》1993,70(10):1393-1396
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Physics of Atomic Nuclei - Various flow effects of nuclear and hadronic origin are investigated in nucleus-nucleus collisions. Nuclear emulsion data collected from 84Kr + Ag/Br interaction at an... 相似文献
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G.H. Liu Y.G. Ma X.Z. Cai D.Q. Fang W.Q. Shen W.D. Tian K. Wang 《Physics letters. [Part B]》2008,663(4):312-316
Hard photon emitted from energetic heavy ion collisions is of very interesting since it does not experience the late-stage nuclear interaction, therefore it is useful to explore the early-stage information of matter phase. In this work, we have presented a first calculation of azimuthal asymmetry, characterized by directed transverse flow parameter F and elliptic asymmetry coefficient v2, for proton–neutron bremsstrahlung hard photons in intermediate energy heavy-ion collisions. The positive F and negative v2 of direct photons are illustrated and they seem to be anti-correlated to the corresponding free proton's flow. 相似文献
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T. Gaitanos C. Fuchs H.H. Wolter A. Faessler 《The European Physical Journal A - Hadrons and Nuclei》2001,12(4):421-433
We investigate differential in-plane and out-of-plane flow observables in heavy-ion reactions at intermediate energies from
0.2-2 AGeV within the framework of relativistic BUU transport calculations. The mean field is based on microscopic Dirac-Brueckner-Hartree-Fock
(DB) calculations. We apply two different sets of DB predictions, those of ter Haar and Malfliet and more recent ones from
the Tübingen group, which are similar in general but differ in details. The latter DB calculations exclude spurious contributions
from the negative-energy sector to the mean field which results in a slightly softer equation of state and a less repulsive
momentum dependence of the nucleon-nucleus potential at high densities and high momenta. For the application to heavy-ion
collisions in both cases non-equilibrium features of the phase space are taken into account on the level of the effective
interaction. The systematic comparison to experimental data favours the less repulsive and softer model. Relative to non-relativistic
approaches one obtains larger values of the effective nucleon mass. This produces a sufficient amount of repulsion to describe
the differential flow data reasonably well.
Received: 8 January 2001 / Accepted: 12 November 2001 相似文献
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Brill D Ahner W Baltes P Barth R Bormann C Cieslak M Debowski M Grosse E Henning W Koczon P Kohlmeyer B Miskowiec D Müntz C Oeschler H Pöppl H Pühlhofer F Sartorius S Schicker R Senger P Shin Y Speer J Stein J Stiebing K Stock R Ströbele H Völkel K Wagner A Walus W 《Physical review letters》1993,71(3):336-339
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D. Brill P. Beckerle C. Bormann E. Schwab Y. Shin H. Ströbele P. Baltes C. Müntz H. Oeschler C. Sturm A. Wagner R. Barth M. Cieslak M. Dȩbowski E. Grosse P. Koczoń M. Mang D. Miśkowiec R. Schicker P. Senger B. Kohlmeyer F. Pühlhofer J. Speer K. Völkel W. Waluś 《Zeitschrift für Physik A Hadrons and Nuclei》1997,357(2):207-213
Triple differential cross-sections of midrapidity pions from 209Bi+209Bi collisions were measured with the Kaon Spectrometer at SIS at incident energies of 400, 700 and 1000 AMeV. The azimuthal emission pattern of the pions has been investigated in dependence of beam energy and impact parameter. An enhanced emission of pions perpendicular to the reaction plane is observed. The strength of the anisotropy increases with beam energy and pion transverse momentum. In contrast to the nucleons the anisotropy varies only little with the impact parameter. No difference in the behaviour of positive and negative pions is observed. 相似文献
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Kang Seog Lee U. Heinz E. Schnedermann 《Zeitschrift fur Physik C Particles and Fields》1990,48(3):525-541
The particle transverse momentum spectra recently measured in relativistic heavy-ion collisions at CERN and BNL are analysed within an expanding fireball model. All the particle spectra at a given beam energy can be reproduced simultaneously with a single set of intensive parameters for the initial state of the fireball. As typical freeze-out parameters in this beam energy region we find a freeze-out temperatureT f?110 MeV for most hadrons, and an average transverse expansion velocity at freeze-out of 〈v/c〉?0.4–0.45. The striking enhancement at transverse momentap T<200 MeV/c in the CERN pion data cannot be fully explained by the existence of transverse flow. 相似文献
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P. Bürgy G. Bonani E. Morenzoni M. Stöckli Ch. Stoller M. Suter W. Wölfli 《Zeitschrift für Physik A Hadrons and Nuclei》1981,300(1):105-106
The dependence of molecular X-ray emission on the azimuthal angle in heavy ion collisions has been measured as a function of the impact parameter in the collision systems F-Al and Cl-Cl at projectile energies of 20 and 48 MeV respectively. The values of the observed azimuthal anisotropies agree with dynamical calculations of molecular orbital X-ray emission, but they are at variance with predictions of the kinematic dipole model. 相似文献
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I. P. Lokhtin S. V. Petrushanko L. I. Sarycheva A. M. Snigirev 《Physics of Atomic Nuclei》2002,65(5):943-952
The question is investigated of whether an azimuthal asymmetry in the hadron-jet spectra can arise because of rescattering and energy losses of partons produced via hard processes in a dense quark-gluon matter formed in the region of the initial nuclear overlap in collisions characterized by a nonzero value of the impact parameter. Methods are discussed for determining the reaction-plane angle in ultrarelativistic heavy-ion collisions with the aid of the flux of semihard particles. 相似文献
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Wang S Lisa MA Albergo S Bieser F Brady FP Caccia Z Cebra DA Chacon AD Chance JL Choi Y Costa S Elliott JB Gilkes ML Hauger JA Hirsch AS Hjort EL Insolia A Justice M Keane D Kintner J Lindenstruth V Liu H Matis HS McMahan M McParland C Olson DL Partlan MD Porile NT Potenza R Rai G Rasmussen J Ritter HG Romanski J Romero JL Russo GV Scharenberg RP Scott A Shao Y Srivastava BK Symons TJ Tincknell ML Tuvè C Warren PG Weerasundara D Wieman HH Wolf KL 《Physical review letters》1996,76(21):3911-3914
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We present a possible collective gluon emission effect based upon a string-like scenario (available if the QCD vacuum works like a color-superconductor type II, i.e. when the color force fields work like vortex-lines) and provide some detailed predictions on the Cronin effect, as well as on an increased (mini)jet production in the center of phase-space in high energy heavy ion collisions. 相似文献
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M.B. Tsang Z. ChajeckiD. Coupland P. DanielewiczF. Famiano R. HodgesM. Kilburn F. LuW.G. Lynch J. WinkelbauerM. Youngs Y.X. Zhang 《Progress in Particle and Nuclear Physics》2011,66(2):400-404
Constraints on the equation of state (EoS) for symmetric matter (equal neutron and proton numbers) have been extracted from energetic collisions of heavy ions over a range of energies. Collisions of neutron-deficient and neutron-rich heavy ions now provide initial constraints on the EoS of neutron-rich matter at subsaturation densities from isospin diffusions and neutron proton ratios. This article reviews the experimental constraints on the density dependence of symmetry energy at subsaturation density. 相似文献
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The collision dynamics of 96Mo + 96Mo at 55 A MeV is simulated by solving numerically the Boltzmann-Uehling-Uhlenbeck (BUU) transport equation for the one-body phase-space distribution-function of nucleons with and without Coulomb interaction. A scatter-plot of the one-body density distribution shows an initial compression, subsequent homogeneous expansion, a breaking into “fragments”, a very slow creeping expansion up to a freeze-out and in the case of included Coulomb-interaction a Coulomb-explosion. In the calculation which included Coulomb-interaction the overall shape of the ensemble of dense fragments is spherical. The fragments are created over the entire volume of the dense part of the source and not at the surface only. In the simulation without Coulomb interaction a doughnut-like shape may develop. 相似文献
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William D. Myers 《Nuclear Physics A》1978,296(1):177-188
A model is developed for high-energy heavy-ion collisions that treats the variation across the overlap region of the target and projectile in the amount of energy and momentum that is deposited. The expression for calculating any observable takes the form of a sum over a series of terms, each one of which consists of a geometric, a kinematic, and a statistical factor. The geometrical factors for a number of target projectile systems are tabulated. 相似文献