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ABSTRACT: The dynamical development of expanding Quark-gluon Plasma (QGP) flow is
studied in a 3+1D fluid dynamical model with a globally symmetric, initial
condition. We minimize fluctuations arising from complex dynamical processes at
finite impact parameters and from fluctuating random initial conditions to have
a conservative fluid dynamical background estimate for the statistical
distributions of the thermodynamical parameters. We also avoid a phase
transition in the equation of state, and we let the matter supercool during the
expansion.
Then central Pb+Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV are studied in an
almost perfect fluid dynamical model, with azimuthally symmetric initial state
generated in a dynamical flux-tube model. The general development of
thermodynamical extensives are also shown for lower energies.
We observe considerable deviations from a thermal equilibrium source as a
consequence of the fluid dynamical expansion arising from a least fluctuating
initial state.
05/2012;
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ABSTRACT: Heavy ion reactions and other collective dynamical processes are frequently described by different theoretical approaches for the different stages of the process, like initial equilibration stage, intermediate locally equilibrated fluid dynamical stage and final freeze-out stage. For the last stage the best known is the Cooper-Frye description used to generate the phase space distribution of emitted, non-interacting, particles from a fluid dynamical expansion/explosion, assuming a final ideal gas distribution, or (less frequently) an out of equilibrium distribution. In this work we do not want to replace the Cooper-Frye description, rather clarify the ways how to use it and how to choose the parameters of the distribution, eventually how to choose the form of the phase space distribution used in the Cooper-Frye formula. Moreover, the Cooper-Frye formula is used in connection with the freeze-out problem, while the discussion of transition between different stages of the collision is applicable to other transitions also. More recently hadronization and molecular dynamics models are matched to the end of a fluid dynamical stage to describe hadronization and freeze-out. The stages of the model description can be matched to each other on spacetime hypersurfaces (just like through the frequently used freeze-out hypersurface). This work presents a generalized description of how to match the stages of the description of a reaction to each other, extending the methodology used at freeze-out, in simple covariant form which is easily applicable in its simplest version for most applications. Comment: 9 pages, 2 figures
06/2010;
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ABSTRACT: We review how flow observables of ultra-relativistic heavy-ion collisions are influenced by the initial condition, the description of the fluid dynamical (FD) stage and freeze-out (FO). We discuss the effects of the resolution of the FD treatment, the arising smoothing and numerical viscosity, as well as the consequences of final FO. This final FO stage includes confinement and simultaneous formation of constituent quarks. From the energy and momentum conservation at the FO stage pressure change and flow velocity may occur, which further modifies the observables.
Journal of Physics G Nuclear and Particle Physics 05/2009; 36(6):064032. · 4.18 Impact Factor
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PoS. 01/2009;
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ABSTRACT: In this talk I summarize recent findings around the description of axial vector mesons as dynamically generated states from the interaction of pseudoscalar mesons and vector mesons, dedicating some attention to the two $K_1(1270)$ states. Then I review the generation of open and hidden charm scalar and axial states, and how some recent experiment supports the existence of the new hidden charm scalar state predicted. I present recent results showing that the low lying $1/2^+$ baryon resonances for S=-1 can be obtained as bound states or resonances of two mesons and one baryon in coupled channels. Then show the differences with the S=0 case, where the $N^*(1710)$ appears also dynamically generated from the two pion one nucleon system, but the $N^*(1440)$ does not appear, indicating a more complex structure of the Roper resonance. Finally I shall show how the state X(2175), recently discovered at BABAR and BES, appears naturally as a resonance of the $\phi K \bar{K}$ system. Comment: Lectures delivered at the Fourth DAE-BRNS workshop on Hadron Physics, Aligarh, India, Feb. 2008
06/2008;
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ABSTRACT: In this talk I summarize recent findings made on the description of axial vector mesons as dynamically generated states from the interaction of peseudoscalar mesons and vector mesons, dedicating some attention to the two $K_1(1270)$ states. Then I review the generation of open and hidden charm scalar and axial states. Finally, I present recent results showing that the low lying $1/2^+$ baryon resonances for S=-1 can be obtained as bound states or resonances of two mesons and one baryon in coupled channels dynamics.
01/2008;
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ABSTRACT: In this presentation I explain our framework for dynamically generating resonances from the meson meson interaction. Our model generates many poles in the T-matrix which are associated with known states, while at the same time new states are predicted.
12/2007;
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E. Oset,
M. Döring, D. Strottman,
D. Jido,
M. Napsuciale,
K. Sasaki,
C. A. Vaquera-Araujo,
M. Kaskulov,
E. Hernandez,
H. Nagahiro,
S. Hirenzaki
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ABSTRACT: In these lectures I will show some results obtained with the chiral unitary approach applied to the photo and electroproduction of mesons. The results for photoproduction of $\eta \pi^0 p$ and $K^0 \pi^0 \Sigma^+$, together with related reactions will be shown, having with common denominator the excitation of the $\Delta(1700)$ resonance which is one of those dynamically generated in the chiral unitary approach. Then I will show results obtained for the $e^+ e^- \to \phi f_0(980)$ reaction which reproduce the bulk of the data except for a pronounced peak, giving support to a new mesonic resonance, X(2175). Results will also be shown for the electromagnetic form factors of the $N^*(1535)$ resonance, also dynamically generated in this approach. Finally, I will show some results on the photoproduction of the $\omega$ in nuclei, showing that present experimental results claiming a shift of the $\omega$ mass in the medium are tied to a particular choice of background and are not conclusive. One the other hand, the same experimental results show unambiguously a huge increase of the $\omega$ width in the nuclear medium.
12/2007;
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ABSTRACT: We briefly expose our model for generating open and hidden charm resonances and present the most interesting results.
11/2007;
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ABSTRACT: In this talk I present recent developments in the field of hadronic physics and hadrons in the nuclear medium. I review the unitary chiral approach to meson baryon interaction and address the topics of the two dynamically generated $\Lambda(1405)$ resonances, with experiments testing it, the $\Lambda(1520)$ and $\Delta(1700)$ resonances, plus the $\Lambda(1520)$, $\Sigma(1385)$ and $\omega$ in the nuclear medium.
03/2007;
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ABSTRACT: We will study open and hidden charm scalar meson resonances within two different models. The first one is a direct application of a chiral Lagrangian already used to study flavor symmetry breaking in Skyrme models. In another approach to the problem a SU(4) symmetric Lagrangian is built and the symmetry is broken down to SU(3) by identifying currents where heavy mesons are exchanged and suppressing those. Unitarization in couple channels leads to dynamical generation of resonances in both models, in particular a new hidden charm resonance with mass 3.7 GeV is predicted. The small differences between these models and with previous works will be discussed.
01/2007;
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ABSTRACT: Using a chiral unitary approach for meson‐baryon scattering in the strangeness zero sector, where the N∗(1535) and Δ∗(1700) resonances are dynamically generated, we study the reactions γp → π0ηp and γp → π0K0Σ+ at photon energies at which the final states are produced close to threshold. Among several reaction mechanisms, we find the most important is the excitation of the Δ∗(1700) state which subsequently decays into a pseudoscalar meson and the N∗(1535). Hence, the reaction provides useful information with which to test current theories of the dynamical generation of the low‐lying 1/2− and 3/2− states. Predictions are made for cross sections and invariant mass distributions which can be compared with forthcoming experiments at ELSA. © 2006 American Institute of Physics
AIP Conference Proceedings. 07/2006; 842(1):449-451.
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ABSTRACT: We make a study of the π−p→K0π0Λ, π+p→K+π+Λ, , K+π+Σ0, K+π0Σ+, and ηπ+p reactions, in which the basic dynamics is given by the excitation of the Δ∗(1700) resonance which subsequently decays into KΣ∗(1385) or Δ(1232)η. In a similar way we also study the γp→K0π+Λ, K+π−Σ+, K+π+Σ−, K0π0Σ+, and ηπ0p related reactions. The cross sections are proportional to the square of the coupling of Δ∗(1700) to Σ∗K (Δη) for which there is no experimental information but which is provided in the context of coupled channels chiral unitary theory where the Δ∗(1700) is dynamically generated. Within present theoretical and experimental uncertainties one can claim a global qualitative agreement between theory and experiment. We provide a list of items which need to be improved in order to make further progress along these lines.
Physics Letters B. 02/2006;
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ABSTRACT: Using a chiral unitary approach for meson-baryon scattering in the strangeness zero sector, where the $N^*(1535)$ and $\Delta^*(1700)$ resonances are dynamically generated, we study the reactions $\gamma p \to \pi^0 \eta p$ and $\gamma p \to \pi^0 K^0 \Sigma^+$ at photon energies at which the final states are produced close to threshold. Among several reaction mechanisms, we find the most important is the excitation of the $\Delta^*(1700)$ state which subsequently decays into a pseudoscalar meson and the $N^*(1535)$. Hence, the reaction provides useful information with which to test current theories of the dynamical generation of the low-lying $1/2^-$ and $3/2^-$ states. Predictions are made for cross sections and invariant mass distributions which can be compared with forthcoming experiments at ELSA.
11/2005;
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ABSTRACT: Using a chiral unitary approach for meson-baryon scattering in the strangeness zero sector, where the $N^*(1535)$ resonance is dynamically generated, we study the reactions $\gamma p \to \pi^0 \eta p$ and $\gamma p \to \pi^0 K^0 \Sigma^+$ at photon energies at which the final states are produced close to threshold. Among several reaction mechanisms, we find the most important is the excitation of the $\Delta^*(1700)$ state which subsequently decays into a pseudoscalar meson and a baryon belonging to the $\Delta(1232)$ decuplet. Hence, the reaction provides useful information with which to test current theories of the dynamical generation of the low-lying $3/2^-$ states. The first reaction is shown to lead to sizable cross sections and the $N^*(1535)$ resonance shape is seen clearly in the $\eta p$ invariant mass distribution. The same dynamical model is shown to lead to much smaller cross sections at low energies in the second reaction. Predictions are made for cross sections and invariant mass distributions which can be compared with forthcoming experiments at ELSA. Comment: 22 pages, 22 figures
10/2005;
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ABSTRACT: Different approaches to describe initial stages of relativistic heavy ion collisions are discussed qualitatively and quantitatively. An Effective String Rope Model is presented for heavy ion collisions at RHIC energies. Our model takes into account baryon recoil for both target and projectile, arising from the acceleration of partons in an effective field, produced in the collision. The typical field strength (string tension) for RHIC energies is about 5-12 GeV/fm, what allows us to talk about ``string ropes''. The results show that a QGP forms a tilted disk, such that the direction of the largest pressure gradient stays in the reaction plane, but deviates from both the beam and the usual transverse flow directions. The produced initial state can be used as an initial condition for further hydrodynamical calculations. Such initial conditions lead to the creation of third flow component. Comment: 47 pages, 14 figures. Minor changes were made, style was changed to "elsart". Paper is accepted to Nucl. Phys. A
02/2002;
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ABSTRACT: A model for energy, pressure and flow velocity distributions at the beginning of relativistic heavy ion collisions is presented, which can be used as initial condition for hydrodynamical calculations. The results show that QGP forms a tilted disk, such that the direction of the largest pressure gradient stays in the reaction plane, but deviates from both the beam and the usual transverse flow directions. Such initial condition may lead to the creation of "antiflow" or "third flow component".
10/2000;
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ABSTRACT: The relativistic extension of non-relativistic hydrodynamics suffers from notorious difficulties. In non-relativistic hydrodynamics where difficulties also abound, it has proved a useful supplement to study lattice models which can imitate viscous uid ow. In this paper we construct a relativistic spacetime lattice and construct a dynamics of points, thus a relativistic cellular automaton over it, to model relativistic uid ow. A simple example is also explicitly studied, and some numerical results with figures are shown in the last section.
Acta Physica Hungarica 10/1999; 9(1):67-98.
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ABSTRACT: Within a relativistic hydrodynamic framework, we use four different equations of state of nuclear matter to compare to experimental
spectra from CERN/SPS experiments NA44 and NA49. Freeze-out hypersurfaces and Bose-Einstein correlation functions for identical
pion pairs are discussed. We find that two-pion Bose-Einstein interferometry measures the relationship between the temperature
and the energy density in the equation of state during the late hadronic stage of the fireball expansion. Little sensitivity
of the light-hadron data to a quark-gluon plasma phase-transition is seen.
European Physical Journal C 09/1999; 10(3):483-486. · 3.63 Impact Factor
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[show abstract]
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ABSTRACT: Within a relativistic hydrodynamic framework, we use four different equations
of state of nuclear matter to compare to experimental spectra from CERN/SPS
experiments NA44 and NA49. Freeze-out hypersurfaces and Bose-Einstein
correlation functions for identical pion pairs are discussed. We find that
two-pion Bose-Einstein interferometry measures the relationship between the
temperature and the energy density in the equation of state during the late
hadronic stage of the fireball expansion. Little sensitivity of the
light-hadron data to a quark-gluon plasma phase-transition is seen.
09/1998;
