共查询到20条相似文献,搜索用时 15 毫秒
1.
A.B. Larionov W. Cassing M. Effenberger U. Mosel 《The European Physical Journal A - Hadrons and Nuclei》2000,7(4):507-518
The proton–charged pion correlated emission is studied in the reactions Au (1.06 AGeV) + Au, Ni (1.06 and 1.93 AGeV) + Ni
and Ni (1.97 AGeV) + Cu within the BUU approach. The associated invariant mass distributions are shifted to smaller energies
with respect to the free Δ(1232) mass distribution due to kinematical reasons. We find that the existing and partly conflicting
experimental data do not allow to draw definite conclusions on the in-medium modification of the Δ(1232).
Received: 18 October 1999 / Revised version: 4 February 2000 相似文献
2.
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
3.
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
4.
Bhaskar De S. Bhattacharyya 《The European Physical Journal A - Hadrons and Nuclei》2001,10(4):387-393
The average phase space density (APSD) of the particles produced in high energy nuclear collisions at ultrarelativistic energies
has here been theoretically estimated on the basis of some particular models for particle production spectra. The model-based
values so obtained have been compared with the very recent experimental results in the field on the relevant observable and
also with the calculated results obtained by some other models. Based on such comparisons, the present work indicates very
strongly that Hagedorn's model has a sound potentiality to achieve a competitive status in its capability to deal with the
data on the APSD factor in heavy-ion collisions. The impact and implications of all this have also been emphasised here in
the end.
Received: 14 November 2000 / Accepted: 19 April 2001 相似文献
5.
Antiproton (ˉp) and antilambda (ˉΛ) production has been measured for minimum bias in p+A collisions and central A1+ A2 collisions at the CERN-SPS by the collaborations NA35/49 and NA44. The measurements are extrapolated from rapidity distributions
to absolute minimum bias cross sections. It is shown that the ˉp cross sections divided by A1· A2 follow an exponential trend as a function of a characteristic length obtained from a Glauber type absorption model, while
the ˉΛ cross sections divided by A1· A2 are constant. The exponential trend also holds for ˉp production at the lower energies of the Brookhaven AGS. A discussion of the physics interpretation of the established trends
in terms of an effective absorption cross section is presented.
Received: 15 July 1999 / Revised version: 10 November 1999 相似文献
6.
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
7.
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
8.
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
9.
W. Broniowski W. Florkowski B. Hiller 《The European Physical Journal A - Hadrons and Nuclei》2000,7(2):287-291
We calculate the width for the ω→ππ decay in nuclear matter in a hadronic model including mesons, nucleons and Δ isobars.
We find a substantial width of the longitudinally polarized ω modes, reaching ∼100 MeV for mesons moving suitably fast with
respect to the nuclear medium.
Received: 7 June 1999 / Revised version: 14 October 1999 相似文献
10.
H. Sakurai 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):49-53
Recent studies on nuclear structure by using radioactive isotope beams available at the RIKEN projectile-fragment separator
(RIPS) are introduced. Special emphasis is given to two selected experiments from recent programs that highlight studies on
the magicity loss observed for very neutron-rich nuclei beyond N = 20 in the “island-of-inversion” region; the particle stability of 31F, and the low-lying excited states of 34Mg.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
11.
12.
G.I. Lykasov W. Cassing A. Sibirtsev M.V. Rzjanin 《The European Physical Journal A - Hadrons and Nuclei》1999,6(1):71-81
We calculate the elastic and inelastic ωN→ωN, →πN, →ρN, →ρπN, →ππN, →σN reactions within a boson exchange approximation where the ωρπ coupling constant and form factor are fixed by the reaction
πN→ωN in comparison to the experimental data. We find rather large ωN cross sections at low relative momenta of the ω-meson which
leads to a substantial broadening of the ω-meson width in nuclear matter. The implications of the ωN final state interactions are studied for ω production in 12C +12C, 40Ca +40Ca and 58Ni +58Ni reactions at about 2 · A GeV within the HSD transport approach; the drastic changes of the transverse mass spectra relative
to a general m
T-scaling (for π0 and η mesons) might be controlled experimentally by the TAPS Collaboration.
Received: 28 April 1999 / Revised version: 7 June 1999 相似文献
13.
J.E. Amaro M.B. Barbaro J.A. Caballero T.W. Donnelly A. Molinari 《The European Physical Journal A - Hadrons and Nuclei》2002,15(4):421-427
The impact of Hartree-Fock correlations on the nuclear momentum distribution is studied in a fully relativistic one-boson-exchange
model. Hartree-Fock equations are exactly solved to first order in the coupling constants. The renormalization of the Dirac
spinors in the medium is shown to affect the momentum distribution, as opposed to what happens in the non-relativistic case.
The unitarity of the model is shown to be preserved by the present renormalization procedure.
Received: 7 June 2002 / Accepted: 24 September 2002 / Published online: 10 December 2002
RID="a"
ID="a"e-mail: juan@nucle.us.es
Communicated by G. Orlandini 相似文献
14.
C.A. Gagliardi A. Azhari V. Burjan F. Carstoiu V. Kroha A.M. Mukhamedzhanov A. Sattarov X. Tang L. Trache R.E. Tribble 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):227-232
Peripheral transfer reactions can be used to determine asymptotic normalization coefficients (ANCs). These coefficients, which
specify the normalization of the tail of the nuclear overlap function, determine S-factors for direct capture reactions at astrophysical energies. A variety of proton transfer reactions involving both stable
and radioactive beams have been used to measure ANCs. Tests have demonstrated that ANCs determined from proton transfer reactions
can be used to calculate astrophysical direct capture rates to within 9%. The 10B(7Be, 8B)9Be and 14N(7Be, 8B)13C reactions have been used to measure the ANC appropriate for determining the 7Be(p,γ)8B rate, and the 14N(11C, 12N)13C reaction has been used to measure the ANC required to calculate the 11C(p,γ)12N rate.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
15.
J. Pluta K. Wosińska Z. Basrak G. Bizard B. Benoit P. Désesquelles O. Dorvaux D. Durand B. Erazmus F. Hanappe B. Jakobsson C. Lebrun F.R. Lecolley R. Lednicky P. Leszczyński K. Mikhailov K. Miller B. Noren T. Pawlak M. Przewłocki Ö. Skeppstedt A. Staranowicz A. Stavinskiy L. Stuttgé B. Tamain 《The European Physical Journal A - Hadrons and Nuclei》2000,9(1):63-68
16.
D. Pierroutsakou A. Boiano A. De Rosa M. Di Pietro G. Inglima M. La Commara Ruhan Ming B. Martin R. Mordente A. Ordine F. Rizzo V. Roca M. Romoli M. Sandoli F. Soramel L. Stroe M. Trotta E. Vardaci 《The European Physical Journal A - Hadrons and Nuclei》2003,17(1):71-76
The 32S + 100Mo and 36S + 96Mo fusionlike reactions were studied at incident energy of E
lab = 298 MeV and 320 MeV, respectively, with the aim of probing the influence of the entrance channel charge asymmetry on the
dipole γ-ray emission. The excitation energy and spin distribution of the compound nucleus created in these reactions were
identical, the only difference being associated with the unequal charge asymmetry of the two entrance channels. High-energy
γ-rays were detected in an array of 9 seven-pack BaF2 clusters. Coincidence with fusionlike residues detected in four PPAC ensured the selection of central reaction events. By
studying the differential γ-ray multiplicity associated with the two reactions it was shown that the dipole strength excited
in the compound nucleus increases with the entrance channel charge asymmetry. From the linearized spectra, the increase of
the GDR γ-ray intensity was found to be ∼ 25% for the more charge asymmetric system. The results are discussed and compared
with those of previous data obtained at different incident energies.
Received: 21 October 2002 / Accepted: 23 December 2002 / Published online: 1 April 2003 相似文献
17.
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
18.
H. Toki 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):177-180
We critically review the present relativistic mean-field theory from the viewpoint of missing pions. We introduce the interesting
experimental data on pionic states taken at RCNP. These data seem to suggest the occurrence of pion condensation in the nuclear
surface. Qualitative discussion is made on the consequence of surface pion condensation on Gamow-Teller transitions and spin
response functions and others. The radioactive ion beams are the tools of studying the unstable nuclei, which have extended
nuclear surfaces. We shall start with radioactive ion beams the nuclear surface science, which includes the surface pion condensation
as the important ingredient in addition to spin-orbit splitting and surface pairing.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
19.
Synthesis and decay properties of superheavy atoms in nuclear reactions induced by stable and radioactive ion beams 总被引:2,自引:0,他引:2
Yu. Oganessian 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):135-141
This talk consists of two parts. The first one presents the results of investigations performed in 1998-2000 in Dubna on the
synthesis of superheavy nuclei in reactions induced by 48Ca ions. The radioactive decay properties of the nuclei, indicating a considerable increase in the α-decay and spontaneous
fission half-lives of the isotopes of elements 110-116 when approaching the closed neutron shell at N = 184, are given. In the second part the possible ways of advancing into the region of more neutron-rich nuclei, using stable
and radioactive ion beams, are discussed. Since so far no intense radioactive ion beams are available, some experiments with
stable beams are considered as a test for the suggested ideas.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
20.
M.Y.H. Farag 《The European Physical Journal A - Hadrons and Nuclei》2001,12(4):405-411
Glauber's theory has been adopted to calculate the total heavy-ion reaction cross-sections at high energies. At relatively
low energies, Glauber's total reaction cross-section has been modified in order to take into account the Coulomb field effect
and is called modified Glauber model I. In addition to the Coulomb field effect, the nuclear effect has also been taken into
account in the Glauber model and is called modified Glauber model II. An analytical expression for the transparency function
for heavy-ion reactions, involving the nuclear densities of the colliding ions and the nucleon-nucleon cross- section, has
been obtained within the framework of the modified Glauber models I and II. The transparency and the total reaction cross-sections
of the 12C + 12C collisions are calculated at different bombarding energies. The obtained results are in good agreement with the experimental
data and with previous theoretical calculations.
Received: 26 January 2001 / Accepted: 15 October 2001 相似文献