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[show abstract]
[hide abstract]
ABSTRACT: The implications of parton rearrangement processes on the dynamics of ultra-relativistic heavyion collisions have been investigated.
A microscopic transport approach, namely the quark gluon string model (QGSM) which has been extended for a locally density-dependent
partonic rearrangement and fusion procedure served as the tool for this investigations. The model emulates effectively the
dynamics of a strongly coupled quark plasma and final hadronic interactions. Main QGSM results on anisotropic flow components
v
1 and v
2 at top RHIC energy are compiled. Predictions for the pseudorapidity dependence of directed and elliptic flow in Pb+Pb collisions
under LHC conditions are presented.
KeywordsUltra-relativistic heavy-ion collisions–microscopic quark gluon string model–rearrangement of partons–directed and elliiptic flow
Indian Journal of Physics and Proceedings of the Indian Association for the Cultivation of Science -New Series- 04/2012; 84(12):1777-1781. · 0.38 Impact Factor
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J. Knoll,
J. Randrup, C. Fuchs,
J. Aichelin,
M. Bleicher,
E. Bratkovskaya,
W. Cassing,
P. Danielewicz,
Y. Ivanov,
B. Kämpfer,
C.-M. Ko,
A. Larionov,
H. Petersen,
V. Toneev
[show abstract]
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ABSTRACT: 1
Introduction
2
Cascade models
3
Kinetic transport models
4
Many-body models
5
Fluid dynamics
6
Characteristic results
7
Status, perspectives and challenges
03/2011: pages 531-680;
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J Knoll,
J Randrup, C Fuchs,
J Aichelin,
M Bleicher,
E Bratkovskaya,
W Cassing,
P Danielewicz,
Y Ivanov,
B Kämpfer,
others
The CBM Physics Book. 01/2011;
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Lect.Notes Phys. 01/2011; 814:531-680.
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E E Zabrodin,
I C Arsene,
J Bleibel,
M Bleicher,
L V Bravina,
G Burau,
Amand Faessler, C Fuchs,
M S Nilsson,
K Tywoniuk,
H Stöcker
[show abstract]
[hide abstract]
ABSTRACT: Two microscopic models, UrQMD and QGSM, are used to extract the effective equation of state (EOS) of locally equilibrated nuclear matter produced in heavy-ion collisions at energies from 11.6 A GeV to 160 A GeV. Analysis is performed for the fixed central cubic cell of volume V = 125 fm3 and for the expanding cell that followed the growth of the central area with uniformly distributed energy. For all reactions the state of local equilibrium is nearly approached in both models after a certain relaxation period. The EOS has a simple linear dependence P = c2sε with 0.12 ≤ c2s ≤ 0.145. Heavy resonances are shown to be responsible for deviations of the c2s(T) and c2s(μB) from linear behavior. In the T–μB and T–μS planes the EOS has also almost linear dependence and demonstrates kinks related not to the deconfinement phase transition but to inelastic freeze-out in the system.
Journal of Physics G Nuclear and Particle Physics 05/2009; 36(6):064065. · 4.18 Impact Factor
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E. Zabrodin,
I. C. Arsene,
J. Bleibel,
M. Bleicher,
L. V. Bravina,
G. Burau,
Amand Faessler, C. Fuchs,
M. S. Nilsson,
K. Tywoniuk,
H. Stoecker
[show abstract]
[hide abstract]
ABSTRACT: Two microscopic models, UrQMD and QGSM, are used to extract the effective equation of state (EOS) of locally equilibrated nuclear matter produced in heavy-ion collisions at energies from 11.6 AGeV to 160 AGeV. Analysis is performed for the fixed central cubic cell of volume V = 125 fm**3 and for the expanding cell that followed the growth of the central area with uniformly distributed energy. For all reactions the state of local equilibrium is nearly approached in both models after a certain relaxation period. The EOS has a simple linear dependence P/e = c_s**2 with 0.12 < c_s**2 < 0.145. Heavy resonances are shown to be responsible for deviations of the c_s**2(T) and c_s**2(mu_B) from linear behavior. In the T-mu_B and T-mu_S planes the EOS has also almost linear dependence and demonstrates kinks related not to the deconfinement phase transition but to inelastic freeze-out in the system. Comment: SQM2008 proceedings, 6 pages
02/2009;
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[show abstract]
[hide abstract]
ABSTRACT: We report on a self-consistent calculation of the in-medium spectral functions of the rho and omega mesons at finite baryon density. The corresponding in-medium dilepton spectrum is generated and compared with HADES data. We find that an iterative calculation of the vector meson spectral functions provides a reasonable description of the experimental data. Comment: Talk given at International School of Nuclear Physics, 30th Course, "Heavy Ion Collisions from the Coulomb Barrier to the Quark Gluon Plasma", Erice, Italy, 16-24 Sep 2008
Progress in Particle and Nuclear Physics 11/2008; 62:479. · 2.61 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The sigma meson production in p + 12C and p + 40Ca reactions at the incident energy Ep = 1.5 GeV is investigated within the Quantum Molecular Dynamics model. The simulation results indicate a distinctive A dependence of the sigma production, that is, the increase of A is followed by an increase of the production cross sections. We find that the σ meson production in proton-induced reactions is strongly medium-dependent, and the produced σ mesons decaying in a denser medium experience a stronger mass shift towards lower masses. This mass shift is an experimentally accessible observable in the final state pion pairs, which do not suffer from reabsorption by the surrounding nucleons. It is pointed out that the ratio of measured sigma cross sections as a function of the sigma invariant-mass from various reactions is a good probe to explore the existence of the σ meson in a dense nuclear environment.
Communications in Theoretical Physics 10/2008; 50(3):725. · 0.75 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The implications of parton rearrangement processes on the dynamics of
ultra-relativistic heavy-ion collisions have been investigated. A microscopic
transport approach, namely the quark gluon string model (QGSM) which has been
extended for a locally density-dependent partonic rearrangement and fusion
procedure served as the tool for this investigations. The model emulates
effectively the dynamics of a strongly coupled quark plasma and final hadronic
interactions. Main QGSM results on anisotropic flow components v1 and v2 at top
RHIC energy are compiled. Predictions for the pseudorapidity dependence of
directed and elliptic flow in Pb+Pb collisions under LHC conditions are
presented.
05/2008;
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[show abstract]
[hide abstract]
ABSTRACT: The in-medium spectral functions of $\rho$ and $\omega$ mesons and the broadening of the nucleon resonances at finite baryon density are calculated self-consistently by combining a resonance dominance model for the vector meson production with an extended vector meson dominance model. The influence of the in-medium modifications of the vector meson properties on the dilepton spectrum in heavy-ion collisions is investigated. The dilepton spectrum is generated for the C+C reaction at 2.0$A$ GeV and compared with recent HADES Collaboration data. The collision dynamics is then described by the T\"ubingen relativistic quantum molecular dynamics transport model. We find that an iterative calculation of the vector meson spectral functions that takes into account the broadening of the nucleon resonances due to their increased in-medium decay branchings is convergent and provides a reasonable description of the experimental data in the mass region $0.45\leq M \leq 0.75$ GeV. On the other side, the theoretical calculations slightly underestimate the region $m_\pi\leq M \leq 0.4$ GeV. Popular in-medium scenarios such as a schematic collisional broadening and dropping vector mesons masses are discussed as well.
Physical Review C 05/2008; 78:034910. · 3.31 Impact Factor
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L. Bravina,
I. Arsene,
J. Bleibel,
M. Bleicher,
G. Burau,
Amand Faessler, C. Fuchs,
M. S. Nilsson,
H. Stoecker,
K. Tywoniuk,
E. Zabrodin
[show abstract]
[hide abstract]
ABSTRACT: Two microscopic models, UrQMD and QGSM, were employed to study the formation of locally equilibrated hot and dense nuclear matter in heavy-ion collisions at energies from 11.6 AGeV to 160 AGeV. Analysis was performed for the fixed central cubic cell of volume V = 125 fm**3 and for the expanding cell which followed the growth of the central area with uniformly distributed energy. To decide whether or not the equilibrium was reached, results of the microscopic calculations were compared to that of the statistical thermal model. Both dynamical models indicate that the state of kinetic, thermal and chemical equilibrium is nearly approached at any bombarding energy after a certain relaxation period. The higher the energy, the shorter the relaxation time. Equation of state has a simple linear dependence P = a(sqrt{s})*e, where a = c_s**2 is the sound velocity squared. It varies from 0.12 \pm 0.01 at E_{lab} = 11.6 AGeV to 0.145 \pm 0.005 at E_{lab} = 160 AGeV. Change of the slope in a(sqrt{s}) behavior occurs at E_{lab} = 40 AGeV and can be assigned to the transition from baryon-rich to meson-dominated matter. The phase diagrams in the T - mu_B plane show the presence of kinks along the lines of constant entropy per baryon. These kinks are linked to the inelastic (i.e. chemical) freeze-out in the system.
05/2008;
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[show abstract]
[hide abstract]
ABSTRACT: The phase-space paths introduced by Cheuk-Yin Wong in Phys. Rev.C25, 1460 (1982) and discussed recently in the literature can be used for calculation of evolution of the Wigner function to first order in the time increments only. The first-order solutions are helpful to determine the phase-space Green function in the framework of the phase-space path integral method.
Physical Review C 10/2007; 76:059801. · 3.31 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: In quantum mechanics, systems can be described in phase space in terms of the Wigner function and the star-product operation. Quantum characteristics, which appear in the Heisenberg picture as the Weyl's symbols of operators of canonical coordinates and momenta, can be used to solve the evolution equations for symbols of other operators acting in the Hilbert space. To any fixed order in the Planck's constant, many-body potential scattering problem simplifies to a statistical-mechanical problem of computing an ensemble of quantum characteristics and their derivatives with respect to the initial canonical coordinates and momenta. The reduction to a system of ordinary differential equations pertains rigorously at any fixed order in ħ. We present semiclassical expansion of quantum characteristics for many-body scattering problem and provide tools for calculation of average values of time-dependent physical observables and cross sections. The method of quantum characteristics admits the consistent incorporation of specific quantum effects, such as non-locality and coherence in propagation of particles, into the semiclassical transport models. We formulate the principle of stationary action for quantum Hamilton's equations and give quantum-mechanical extensions of the Liouville theorem on conservation of the phase-space volume and the Poincaré theorem on conservation of 2p-forms. The lowest order quantum corrections to the Kepler periodic orbits are constructed. These corrections show the resonance behavior.
Annalen der Physik 09/2007; 16(9):587 - 614. · 0.84 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Dileptons represent a unique probe for nuclear matter under extreme conditions reached in heavy-ion collisions. They allow the study of meson properties, like mass and decay width, at various density and temperature regimes. We use the extended vector meson dominance (eVMD) model developed in Tübingen to determine the in-medium properties of the ρ and ω vector mesons by computing their in-medium spectral functions. Contributions to the in-medium self-energies due to excitation of nucleonic resonances are supplemented by non-resonant Compton scattering and σ meson exchange terms. Dilepton spectra for C+C heavy-ion collisions at 1.0 and 2.0 AGeV within spectral function approach and the traditional Brown-Rho scalling/collisional broaden-ing scenario are computed and compared. Finally, a preliminary comparison with the available HADES collaboration experimental data for C+C at 2.0 AGeV is presented, revealing an impor-tant discrepancy in the 0.2-0.7 GeV invariant mass region.
PoS. 02/2007; CPOD07:036.
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[show abstract]
[hide abstract]
ABSTRACT: We present Dirac-Brueckner-Hartree-Fock calculations for isospin asymmetric nuclear matter which are based on improved approximations schemes. The potential matrix elements have been adapted for isospin asymmetric nuclear matter in order to account for the proton-neutron mass splitting in a more consistent way. The proton properties are particularly sensitive to this adaption and its consequences, whereas the neutron properties remains almost unaffected in neutron rich matter. Although at present full Brueckner calculations are still too complex to apply to finite nuclei, these relativistic Brueckner results can be used as a guidance to construct a density dependent relativistic mean field theory, which can be applied to finite nuclei. It is found that an accurate reproduction of the Dirac-Brueckner-Hartree-Fock equation of state requires a renormalization of these coupling functions. Comment: 34 pages, 9 figures, submitted to Eur. Phys. J. A
12/2006;
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[show abstract]
[hide abstract]
ABSTRACT: The implications of parton recombination processes on the dynamics of ultrarelativistic heavy-ion reactions are investigated. To do so, the quark-gluon string transport model has been extended for partonic recombination and fusion processes. Parton recombination leads to short equilibration times and improves significantly on the theoretical description of measured directed and elliptic flow, i.e., v_1 and v_2, distributions in Au+Au collisions at sqrt(s) = 200 GeV, in particular what concerns their pseudorapidity dependence. The shape of v_2(eta) is found to be closely related to fast thermalization.
11/2006;
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T. Klähn,
D. Blaschke,
S. Typel,
E. N. E. van Dalen,
A. Faessler, C. Fuchs,
T. Gaitanos,
H. Grigorian,
A. Ho,
E. E. Kolomeitsev,
M. C. Miller,
G. Röpke,
J. Trümper,
D. N. Voskresensky,
F. Weber,
H. H. Wolter
[show abstract]
[hide abstract]
ABSTRACT: A new scheme for testing nuclear matter equations of state (EoSs) at high densities using constraints from neutron star (NS) phenomenology and a flow data analysis of heavy-ion collisions is suggested. An acceptable EoS shall not allow the direct Urca process to occur in NSs with masses below 1.5M⊙, and also shall not contradict flow and kaon production data of heavy-ion collisions. Compact star constraints include the mass measurements of 2.1±0.2M⊙ (1σ level) for PSR J0751+1807 and of 2.0±0.1M⊙ from the innermost stable circular orbit for 4U 1636–536, the baryon mass—gravitational mass relationships from Pulsar B in J0737–3039 and the mass-radius relationships from quasiperiodic brightness oscillations in 4U 0614+09 and from the thermal emission of RX J1856–3754. This scheme is applied to a set of relativistic EoSs which are constrained otherwise from nuclear matter saturation properties. We demonstrate on the given examples that the test scheme due to the quality of the newly emerging astrophysical data leads to useful selection criteria for the high-density behavior of nuclear EoSs.
Phys. Rev. C. 09/2006; 74(3).
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[show abstract]
[hide abstract]
ABSTRACT: It is a well known fact that Dirac phenomenology of nuclear forces predicts the existence of large scalar and vector mean fields in matter. To analyse the relativistic self-energy in a model independent way, modern high precision nucleon-nucleon ($NN$) potentials are mapped on a relativistic operator basis using projection techniques. This allows to compare the various potentials at the level of covariant amplitudes were a remarkable agreement is found. It allows further to calculate the relativistic self-energy in nuclear matter in Hartree-Fock approximation. Independent of the choice of the nucleon-nucleon interaction large scalar and vector mean fields of several hundred MeV magnitude are generated at tree level. In the framework of chiral EFT these fields are dominantly generated by contact terms which occur at next-to-leading order in the chiral expansion. Consistent with Dirac phenomenology the corresponding low energy constants which generate the large fields are closely connected to the spin-orbit interaction in $NN$ scattering. The connection to QCD sum rules is discussed as well.
08/2006;
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[show abstract]
[hide abstract]
ABSTRACT: We consider the role of rescattering of secondary kaons on the dilepton branching ratio of the phi meson. In-medium mass modifications and broadening of kaons and phi mesons are taken into account. We find in the framework of a Bjorken scenario for the time evolution of the expanding fireball that the phi yield from dimuons is moderately or at least only slightly enhanced compared to that from kaon-antikaon pairs. The relation to experimental yields measured by the NA49, NA50 and CERES Collaborations at CERN SPS and the PHENIX Collaboration at RHIC is discussed. Comment: 6 pages with 2 figures, accepted for publication in Eur. Phys. J. A
05/2006;
-
[show abstract]
[hide abstract]
ABSTRACT: In quantum mechanics, systems can be described in phase space in terms of the
Wigner function and the star-product operation. Quantum characteristics, which
appear in the Heisenberg picture as the Weyl's symbols of operators of
canonical coordinates and momenta, can be used to solve the evolution equations
for symbols of other operators acting in the Hilbert space. To any fixed order
in the Planck's constant, many-body potential scattering problem simplifies to
a statistical-mechanical problem of computing an ensemble of quantum
characteristics and their derivatives with respect to the initial canonical
coordinates and momenta. The reduction to a system of ordinary differential
equations pertains rigorously at any fixed order in $\hbar$. We present
semiclassical expansion of quantum characteristics for many-body scattering
problem and provide tools for calculation of average values of time-dependent
physical observables and cross sections. The method of quantum characteristics
admits the consistent incorporation of specific quantum effects, such as
non-locality and coherence in propagation of particles, into the semiclassical
transport models. We formulate the principle of stationary action for quantum
Hamilton's equations and give quantum-mechanical extensions of the Liouville
theorem on the conservation of phase-space volume and the Poincar\'e theorem on
the conservation of $2p$ forms. The lowest order quantum corrections to the
Kepler periodic orbits are constructed. These corrections show the resonance
behavior.
05/2006;
