共查询到20条相似文献,搜索用时 15 毫秒
1.
We study soft hadron production in relativistic heavy-ion collisions in a wide range of reaction energy, 4.8 GeV <
< 200 GeV, and make predictions about yields of particles using the statistical hadronization model. In fits to experimental
data, we obtain both the statistical parameters as well as physical properties of the hadron source. We identify the properties
of the fireball at the critical energy threshold, 6.26 GeV <
< 7.61 GeV, marking for higher energies the hadronization of an entropy-rich phase. In terms of the chemical composition,
one sees a phase which at low energy is chemically under-saturated, and which turns into a chemically over-saturated state
persisting up to the maximum accessible energy. Assuming that there is no change in physical mechanisms in the energy range
15 >
≥200 GeV, we use continuity of particle yields and statistical parameters to predict the hadron production at
= 62.4 GeV, and obtain total yields of hadrons at
= 130 GeV. We consider, in depth, the pattern we uncover within the hadronization condition, and discuss possible mechanisms
associated with the identified rapid change in system properties at
. We propose that the chemically over-saturated 2 + 1 flavor hadron matter system undergoes a 1st-order phase transition. 相似文献
2.
Transverse-energy and charged-particle pseudorapidity densities at midrapidity and their ratio, dET/d|mid/dNch/d|mid, are evaluated in a statistical model with longitudinal and transverse flows for the wide range of colliders, from AGS to RHIC at
= 200 GeV. Evaluations are done at freeze-out parameters obtained from independent fits to observed particle yields and pT spectra. Decays of hadron resonances are treated thoroughly and are included in derivations of dET/d|mid and dNch/d|mid. The predictions of the model agree well with the experimental data. However, some (explicable) overestimation of the ratio has been observed. 相似文献
3.
4.
5.
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
6.
K. Wosińska J. Pluta F. Hanappe L. Stuttge J. C. Angelique B. Benoit E. de Goes Brennand G. Bizard J. Colin G. Costa P. Desesquelles O. Dorvaux D. Durand B. Erazmus S. Kuleshov R. Lednicky M. Marques Th. Materna K. Mikhailov G. Papatheofanous T. Pawlak A. Staranowicz A. Stavinskiy B. Tamain A. Vlasov L. Vorobyev 《The European Physical Journal A - Hadrons and Nuclei》2007,32(1):55-59
The measurement of the two-particle correlation function for different particle species allows to obtain information about
the development of the particle emission process: the space-time properties of emitting sources and the emission time sequence
of different particles. The single-particle characteristics and two-particle correlation functions for neutral and charged
particles registered in forward direction are used to determine that the heavy fragments (deuterons and tritons) are emitted
in the first stage of the reaction (pre-equilibrium source) while the majority of neutrons and protons originates from the
long-lived quasi-projectile. The emission time sequence of protons, neutrons and deuterons has been obtained from the analysis
of non-identical particle correlation functions. 相似文献
7.
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
8.
B. K. Srivastava 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):862-867
The study of correlations and fluctuations can provide evidence for the production of the quark-gluon plasma (QGP) in relativistic
heavy-ion collisions. Various theories predict that the production of a QGP phase in relativistic heavy-ion collisions could
produce significant event-by-event correlations and fluctuations in transverse momentum, multiplicity, etc. Some of the recent
results using STAR at RHIC will be presented along with results from other experiments at RHIC. The focus is on forward-backward
multiplicity correlations, balance function, charge and transverse-momentum fluctuations, and correlations. 相似文献
9.
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
10.
11.
D. Prorok 《The European Physical Journal A - Hadrons and Nuclei》2006,29(1):127-128
The transverse energy and the charged-particle multiplicity at midrapidity are evaluated in a single-freeze-out model for
different centrality bins at RHIC at
= 130 and 200GeV. The predictions of the model are done at the freeze-out parameters determined earlier from measured particle
yields and pT spectra. The results agree qualitatively well with the experimental data. 相似文献
12.
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
13.
We study the π± spectra obtained in 2, 4, 6 and 8A GeV Au - Au collisions within the thermal model. We find that the main features of the data can be well described after we
include the pions from the decay of the Δ -resonance with medium mass modification. 相似文献
14.
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
15.
We discuss how the dynamics of an exploding hot fireball of quark-gluon matter impacts the actual phase transition conditions
between the deconfined and confined state of matter. We survey the chemical conditions prevailing at hadronization. 相似文献
16.
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
17.
Evidence is presented that diffusion drives colliding many-particle systems at relativistic energies from the initial δ–functions
in rapidity towards the equilibrium distribution. Analytical solutions of a linear Fokker-Planck equation represent rapidity
spectra for participant protons in central heavy-ion collisions at SPS-energies accurately. Thermal equilibrium in the interaction
region is not attained, nonequilibrium features persist and can account for the broad rapidity spectra.
Received: 24 November 1998 / Revised version: 20 February 1999 相似文献
18.
M. Gonçalves M. Chiapparini L. Castro E.C. de Oliveira S.B. Duarte E.L. Medeiros 《The European Physical Journal A - Hadrons and Nuclei》2000,7(3):435-440
The effect of multiparticle correlations on resonance and pion populations, in relativistic nuclear reactions, is calculated
in the context of an intranuclear cascade model which includes N-body (N > 2) collisional processes. The resonance-matter
population present in the highly-compressed phase of nucleus-nucleus collisions is investigated, in reactions between different
intermediate-mass nuclear systems.
Received: 29 December 1998 / Revised version: 20 December 1999 相似文献
19.
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
20.
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