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1.
A. Lang B. Blättel W. Cassing V. Koch U. Mosel K. Weber 《Zeitschrift für Physik A Hadrons and Nuclei》1991,340(3):287-295
Within a covariant BUU-approach we simulate heavyion collisions at various bombarding energies from 400 MeV/u to 1 GeV/u. We evaluate locally the energymomentum tensorT
v
(x), and extract pressures, energydensities and temperatures. The connection of these thermodynamical quantities to experimental observables and their sensitivity to the equation of state is discussed. Furthermore, we investigate the question of local equilibration and evaluate the entropy produced in these reactions.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday. Work supported by BMFT and GSI Darmstadt 相似文献
2.
G. G. Adamian R. V. Jolos A. K. Nasirov 《Zeitschrift für Physik A Hadrons and Nuclei》1994,347(3):203-210
In the single-particle approach a partition of the excitation energy between the reaction products in deep inelastic collisions of heavy ions are investigated. The role of the particle-hole excitations and the nucleon exchange is considered. The ratio of the projectile excitation energy to the total excitation energy for the reactions238U(1468 MeV)+124Sn,238U(1398 MeV)+110Pd,56Fe(505MeV)+165Ho,74Ge (629 MeV)+165Ho and68Ni(880 MeV)+197Au is calculated. The results of calculations are in good agreement with the experimental data.We are grateful to Dr. N.V. Antonenko for valuable discussions. This work was supported partly by the Russian Minister for Education and Research under the Grant N2-61-13-28. 相似文献
3.
S. A. Bass C. Hartnack H. Stöcker W. Greiner 《Zeitschrift für Physik A Hadrons and Nuclei》1995,352(2):171-174
We present a microscopic calculation of neutronsqueeze-out in relativistic heavy ion collisions at beam energies betweeen 400 and 1000 MeV/nucleon. After demonstrating the importance of the correct isospin treatment for the neutron to proton ratio, our main emphasis is put on the investigation of the properties of neutronsqueeze-out. Thesqueeze-out ratio increases monotonously with the transverse momentum of the neutrons. This ratio is independent of the incident beam energy if plotted versusp
t
/p
proj
. Most importantly, we observe a strong dependence on the nuclear equation of state and momentum dependent interaction.Supported by GSI, BMFT and DFG 相似文献
4.
Relativistic corrections for the elastic scattering of heavy ions in the sub Coulomb regime are given. The case of two identical particles is treated especially. The deviation from the Rutherford (Mott) cross section is calculated by using the Todorov equation and the Darwin Hamiltonian, resp. It is shown, that both approches lead to the same results for small kinetic energies. Furthermore we discuss the applicability of the WKB method for calculating the phase shifts and the possibility of using a classical perturbative approach in the case of nonidentical particles. 相似文献
5.
U. Katscher D. H. Rischke J. A. Maruhn W. Greiner I. N. Mishustin L. M. Satarov 《Zeitschrift für Physik A Hadrons and Nuclei》1993,346(3):209-216
A new multi-fluid model is constructed for describing high-energy heavy-ion collisions. It is assumed that two baryonic fluids formed by the projectile and target nucleons produce a third hadronic fluid via inelastic nucleon-nucleon collisions. The production and expansion dynamics of the hadronic fluid are investigated in detail. Two equations of state for this fluid are considered: one corresponding to an ideal gas of pions and resonances and another one corresponding to an interacting hadron gas described by the relativistic mean-field model. The effects of freeze-out and non-zero pion chemical potential are investigated. The rapidity and transverse momentum spectra of secondary pions are compared with the experimental data forS + S collisions at 200 GeV/nucleon.The authors thank J. Schaffner for his most valuable assistance in the application of the mean-field model. The authors are also grateful to H. Sorge and A. Jahns for fruitful discussions. This work was supported by the Gesellschaft für Schwerionenforschung (GSI) and the Bundesministerium für Forschung und Technologie (BMFT). 相似文献
6.
The transverse energy distribution in ultra-relativistic heavy-ion collisions has been obtained as a convolution over the number of projectile and target participants. The latter is computed using the geometrical overlap model as a function of impact parameter. The data from 10 A GeV to 200 A GeV heavy ion beams on various targets in different pseudo-rapidity domains have been successfully described. 相似文献
7.
A. Badalá R. Barbera A. Palmeri G. S. Pappalardo F. Riggi A. C. Russo 《Zeitschrift für Physik A Hadrons and Nuclei》1993,344(4):455-467
Several global variables were tested with the aim to determine the impact parameter in nucleus-nucleus collisions producing pions at incident energies around 100 MeV/nucleon. The experimental set-up includes the MEDEA multidetector, part of which is used as a
0 spectrometer, and an additional hodoscope of plastic scintillators to cover very forward angles. A statistical model was used to generate bothinclusive and pion-triggered events. Selection ofwell measured events was made through the measured total parallel momentum. Among the different global variables which were tested, the average parallel velocity was seen to give the best correlation with the impact parameter. 相似文献
8.
D. Lambrecht T. Blaich T. W. Elze H. Emling H. Freiesleben K. Grimm W. Henning R. Holzmann J. G. Keller H. Klingler J. V. Kratz R. Kulessa S. Lange Y. Leifels E. Lubkiewicz E. F. Moore W. Prokopowicz R. Schmidt C. Schütter H. Spies K. Stelzer J. Stroth E. Wajda W. Waluś M. Zinser E. Zude 《Zeitschrift für Physik A Hadrons and Nuclei》1994,350(2):115-120
We investigate the beam energy dependence of neutron and proton squeeze-out in collisions of197Au+197Au atE/A=400—800 MeV. The azimuthal anisotropy that describes the enhanced emission of mid-rapidity neutrons perpendicular to the reaction plane rises strongly with the transverse momentum of the neutrons. This dependence of the azimuthal anisotropy follows a universal curve — independent of beam energy — if the neutron momenta are measured in fractions of the projectile momentum per mass unit. Analogously, the kinetic energy spectra of mid-rapidity neutrons exhibit a universal behaviour as a function of the kinetic energy of the projectile.
The members of the FOPI-collaboration: J.P. Alard, Z. Basrak, N. Bastid, I.M. Belayev, M. Bini, R. Bock, A. Buta, R. aplar, C. Cerruti, N. Cindro, J.P. Coffin, M. Crouau, P. Dupieux, J. Erö, Z.G. Fan, P. Fintz, Z. Fodor, R. Freifelder, L. Fraysse, S. Frolov, A. Gobbi, Y. Grigorian, G. Guillaume, N. Herrmann, K.D. Hildenbrand, S. Hölbling, O. Houari, S.C. Jeong, M. Jorio, F. Jundt, J. Kecskemeti, P. Koncz, Y. Korchagin, R. Kotte, M. Krämer, C. Kuhn, I. Legrand, A. Lebedev, C. Maguire, V. Manko, T. Matulewicz, G. Mgebrishvili, J. Mösner, D. Moisa, G. Montarou, P. Morel, W. Neubert, A. Olmi, G. Pasquali, D. Pelte, M. Petrovici, G. Poggi, F. Rami, W. Reisdorf, A. Sadchikov, D. Schüll, Z. Seres, B. Sikora, V. Simion, S. Smolyankin, U. Sodan, N. Taccetti, K. Teh, R. Tezkratt, M. Trzaska, M.A. Vasiliev, P. Wagner, J.P. Wessels, T. Wienold, Z. Wilhelmi, D. Wohlfarth, A.V. Zhilin. 相似文献
9.
L. Münchow 《Zeitschrift für Physik A Hadrons and Nuclei》1992,343(1):43-46
Heavy ion reactions at intermediate energies are mostly described by the VUU equations. Using methods of quantum statistics we derive a useful relation between the width of s.p. states and the density — density correlation function. Near the point of instability from this relation there follows the increase of the collision integral and enhanced equilibration.The author thanks Yu. Kalinovsky, R. Nazmitdinov and M. Di Toro for valuable discussions. 相似文献
10.
M. Crippa E. Gadioli P. Vergani G. Ciavola C. Marchetta M. Bonardi 《Zeitschrift für Physik A Hadrons and Nuclei》1994,350(2):121-129
The excitation functions for production of 21 isotopes and isomers of Au, Pt, Ir, Os and Re in the interaction of12C with181Ta from 54 to 98 MeV incident energy have been measured by the activation technique. The analysis of these data allows one to estimate the reaction cross-section and the cross-sections for complete fusion of12C and the incomplete fusion of8Be and fragments with tantalum. 相似文献
11.
G. Perrin H. Dabrowski G. Duhamel-Chrétien D. Lebrun P. de Saintignon R. Bougault D. Durand A. Genoux-Lubain C. Le Brun J. F. Lecolley M. Louvel 《Zeitschrift für Physik A Hadrons and Nuclei》1992,342(2):199-202
Low energy
+ and
– production cross sections have been measured in16O at 65 MeV/u and84Kr at 60 MeV/u induced reactions on7Li,12C,27Al,108Ag and197Au. The results are compared with a previous measurement obtained with16O at 93 MeV/u. Large deviations are observed between light and heavy ion data. At variance with16O, the ratios
–/
+ are independent of the target in the Krypton case. A change in the regime of the projectile-target mass scaling of cross-sections is observed with the heaviest projectile.Experiments performed at GANIL facility, F-14032 Caen, France 相似文献
12.
H. Keller V. Borrel D. Guillemaud-Mueller A. C. Mueller F. Pougheon O. Sorlin P. Baumann F. Didierjean A. Huck A. Knipper G. Walter R. Anne D. Bazin M. Lewitowicz M. G. Saint-Laurent G. Marguier 《Zeitschrift für Physik A Hadrons and Nuclei》1994,348(1):67-68
Beta-coincident-rays were measured from implanted44V and42Sc nuclei. These were selected after58Ni+nickel reactions by means of the LISE3 spectrometer at GANIL. The production of the isomeric states was identified by detecting their typical-delayed-ray cascades. From the intensities of the detected-lines the ratio between isomer and ground-state production of44V follows to be 1 to 3.0(4).on leave of absence from GSI Darmstadt. 相似文献
13.
W. Ahner P. Baltes Ch. Bormann D. Brill R. Brockmann M. Cieślak E. Grosse W. Henning P. Koczoń B. Kohlmeyer W. Konrad D. Miśkowiec Ch. Müntz H. Oeschler H. Pöppl W. Prokopowicz F. Pühlhofer R. Renfordt A. Sandoval S. Sartorius R. Schicker E. Schwab P. Senger Y. Shin J. Stein K. Stiebing R. Stock H. Ströbele K. Völkel A. Wagner W. Waluś 《Zeitschrift für Physik A Hadrons and Nuclei》1991,341(1):123-124
Subthreshold kaon production in197
Au+197
Au collisions at 1.0 GeV/u has been investigated with the Kaon Spectrometer at SIS. At
lab
=44±4 we found aK
+/p ratio of>3 · 10–4 for the momentum range 650 MeV/c to 1150 MeV/c.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday 相似文献
14.
R. Bock K. G. R. Doss H. H. Gutbrod K. -H. Kampert B. Kolb I. Lund H. R. Schmidt T. Siemiarczuk W. Wiślicki 《Zeitschrift für Physik A Hadrons and Nuclei》1992,343(3):293-299
We report transverse,R
T
, and longitudinal,R
L
, source sizes extracted from two-pion interferometry analysis in the Au+Au and Nb + Nb interactions at 650 A MeV. For the Nb+Nb interactions, both,R
T
andR
L
, do not exceed the niobium nucleus radius. In the case of Au+Au collisions, the transverse size is larger than the longitudinal one being about 12 fm for the selection ofP
+ < 120=" mev/c.=" we=" also=" corroborate=" the=" existence=" of=" the=" previously=" reported=" specific=" three-pion=">One of us (T.S.) wishes to thank Professor M.I. Podgoretsky and Professor R.M. Weiner for interesting discussions and comments. We also wish to acknowledge remarks of Dr. B. Lörstad. 相似文献
15.
We report the first measurement of the total charge-loss cross section tot=em+nuc and partial cross sections (for Z=1, 2, ..., 9) of 11.4 A GeV197Au nuclei in various targets. The large Coulomb barrier for Au reduces the electromagnetic contribution em in a Pb target to only 18% of nuc, compared with 70% for 14.5 A GeV28Si and 120% for 200 A GeV32S. With em taken to be Z
T
1.8
, nuc can be fitted with nuc=(A
P
1/3
+A
T
1/3
–b)2, with b=0.83 and =59 mb, essentially the same as found at energies of 1 to 2 A GeV. Electromagnetic partial cross sections for Z=1 exceed 40 mb in the Pb, Sn, Cu, and Fe targets and are substantial for larger values ofZ in the heavier targets.We are indebted to D. Beavis and the staff of the Alternating Gradient Synchrotron at Brookhaven National Laboratory for producing the beam of 11.4 A GeV Au ions, to D. Snowden-Ifft for his efforts in developing the automated scanning system, and to S. Hirzebruch for a useful discussion. This work was supported in part by the Office of Energy Research, Office of High Energy and Nuclear Physics, Division of High Energy Physics, of the Department of Energy under contract No. DEAC03-76SF00098. 相似文献
16.
L. Harzheim M. G. Huber B. C. Metsch 《Zeitschrift für Physik A Hadrons and Nuclei》1991,340(4):399-410
The production of pions in nuclear collisions is analyzed in terms of a microscopic reaction model, where the free energy of the entrance channel is transferred to the final channel through the coupling of the relative motion to the internal excitation of N*-resonances. Such a model allows quite naturally for a consistent analysis of the exclusive and the inclusive production of pions. It turns out that the pionic fusion cross section is determined predominantly by the spectroscopic parentage between the initial target projectile combination and the final nucleus, whereas the inclusive part is dominated by the energy dependence of the phase space factor, i.e. by the number of the degrees of freedom which are relevant in a given kinematical situation. This model is applied to the analysis of available experimental data from threshold to the (1232)-region. A consistent analysis of both the inclusive and the exclusive part of the pion spectrum is presented.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday 相似文献
17.
A. Schröter E. Berdermann H. Geissel A. Gillitzer J. Homolka P. Kienle W. Koenig B. Povh F. Schumacher H. Ströher 《Zeitschrift für Physik A Hadrons and Nuclei》1994,350(2):101-113
Subthreshold ¯p andK
– and energetic
– production was studied in Ne + NaF, Cu, Sn and Bi, and in Ni + Ni collisions with incident energies between 1.6 and 2 GeV/u. The measured cross sections indicate a dominant contribution of baryonic resonances. This is also consistent with a generalized scaling behaviour of the cross sections with the energy available in the collision and the energy necessary to produce particles as observed with Ne induced reactions. Deviations from scaling especially pronounced in the Ni-Ni system will be discussed in terms of absorption effects. The flat slope of the excitation function for ¯p production can be related to a reduced production threshold caused by a reduction of the antiproton mass in the dense and heated medium by about 100—150 MeV/c2. A similar in-medium mass reduction is also indicated forK
– mesons. An increased ¯p reabsorption probability for the heavier systems is concluded from the comparison of the ¯p yields in Ne + NaF, Ne + Sn and Ni + Ni collisions.Dedicated to Professor Klaus Dietrich on the occasion of his 60th birthday. 相似文献
18.
A. J. Cole A. Chabane M. Charvet P. Désesquelles A. Giorni D. Heuer A. Lleres J. B. Viano 《Zeitschrift für Physik A Hadrons and Nuclei》1995,353(3):279-287
We present an analysis which aims at explaining the similarities (and differences) which exist between a simple bond percolation process on a cubic lattice and the fragmentation of highly excited atomic nuclei. Emphasis is placed on discussing percolation in terms of concepts which are well known in nuclear physics such asQ-value and particle emission thresholds. Similarities and differences between the bond percolation process and nuclear fragmentation are discussed. An approximate expression for the microcanonical partition sum (number of microstates) corresponding to any given percolation partition is shown to provide a good starting point for predicting fragment size distributions.Communicated by: X. Campi 相似文献
19.
K. Knoche L. Sprute W. Behrmann E. Mordhorst W. Scobel M. Strecker B. Cramer B. Gebauer D. Hilscher U. Jahnke E. Schwinn 《Zeitschrift für Physik A Hadrons and Nuclei》1992,342(3):319-327
Energy spectra and multiplicities of neutrons from the reaction system 838 MeV32S projectiles on197Au have been measured in coincidence with binary fragmentations. Neutron detection was performed simultaneously in a 4 scintillator sphere and by time-of-flight. The linear momentum transfer (LMT) and the excitation energyE
CN
*
are deduced with the folding angle technique. Neutron multiplicities are compared for consistency and discussed as a measure of LMT andE
CN
*
. The saturation ofM
4
(E
CN
*
) beyondE
CN
*
400 MeV seen for several systems of high fissility (x0.8) is attributed to the spreading of the folding angle distribution and the increasing competition of charged particle evaporation. 相似文献
20.
R. Gentner D. Bellm L. Lassen A. Oberstedt A. Giorni A. Lleres J. -B. Viano B. Cheynis B. Chambon D. Drain 《Zeitschrift für Physik A Hadrons and Nuclei》1993,347(2):117-122
The closely associated phenomena of preequilibrium emission and evaporation residue formation in fusion-like reactions were studied in central collisions between40Ar andnatCa at 30 MeV/u. Heavy reaction products were taken in coincidence with neutrons and light charged particles. The preequilibrium neutron data agree very well with predictions of a quantal phase-space model which, in addition to the mean field, takes two-body collisions properly into account. Preequilibrium emission ends in thermally equilibrated hot nuclei with an average excitation energy of about 6 MeV/u. The combined results show a striking interrelation between the missing mass and light-particle multiplicities: the mass difference between the full compound mass and the observed residues can be explained quantitatively by the emission of only neutrons and light charged particles withZ2 during the entire course of energy dissipation.Supported by the German Bundesministerium für Forschung und Technologie (BMFT) under contract 06 HD 983I 相似文献