arXiv subjects

D. Strottman

Publications and source records attributed to D. Strottman.

34 records · Page 2Linked to original sources

arXiv2004

Possible production of exotic baryonia in relativistic heavy-ion collisions

Properties of a hypothetical baryonium with the quark content ($uds\ov{u}\ov{d}\ov{s}$) are discussed. The MIT bag model predicts its mass to be unexpectedly low, approximately 1210 MeV. Possible hadronic decay modes of this state are analyzed. Ultrarelativistic heavy-ion collisions provide favorable conditions for the formation of such particles from the baryon-free quark-gluon plasma. We estimate multiplicities of such exotic baryonia on the basis of a simple thermal model.

hep-ph↗

arXiv2002

Effective String Rope Model for the initial stages of Ultra-Relativistic Heavy Ion Collisions

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.

hep-ph↗

arXiv2001

Multi Module Model for Ultra-Relativistic Heavy Ion Collisions

The Multi Module Model for Ultra-Relativistic Heavy Ion Collisions at RHIC and LHC energies is presented. It uses the Effective String Rope Model for the calculation of the initial stages of the reaction; the output of this model is used as the initial state for the subsequent one-fluid calculations. It is shown that such an initial state leads to the creation of the third flow component. The hydrodynamical evolution of the energy density distribution is also presented.

hep-ph↗

arXiv2000

The source of elliptic flow and initial conditions for hydrodynamical calculations

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".

nucl-th↗

arXiv1998

Bose-Einstein Correlations and the Equation of State of Nuclear Matter

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.

nucl-th↗

arXiv1998

Time-dependent properties of proton decay from crossing single-particle metastable states in deformed nuclei

A dynamical study of the decay of a metastable state by quantum tunneling through an anisotropic, non separable, two-dimensional potential barrier is performed by the numerical solution of the time-dependent Schrodinger equation. Initial quasi- stationary proton states are chosen in the framework of a deformed Woods-Saxon single-particle model. The decay of two sets of states corresponding to true and quasi levels-crossing is studied and the evolution of their decay properties as a function of nuclear deformation is calculated around the crossing point. The results show that the investigation of the proton decay from metastable states in deformed nuclei can unambiguously distinguish between the two types of crossing and determine the structure of the nuclear states involved.

nucl-th↗

arXiv1998

Various Models for Pion Probability Distributions from Heavy-Ion Collisions

Various models for pion multiplicity distributions produced in relativistic heavy ion collisions are discussed. The models include a relativistic hydrodynamic model, a thermodynamic description, an emitting source pion laser model, and a description which generates a negative binomial description. The approach developed can be used to discuss other cases which will be mentioned. The pion probability distributions for these various cases are compared. Comparison of the pion laser model and Bose-Einstein condensation in a laser trap and with the thermal model are made. The thermal model and hydrodynamic model are also used to illustrate why the number of pions never diverges and why the Bose-Einstein correction effects are relatively small. The pion emission strength $η$ of a Poisson emitter and a critical density $η_c$ are connected in a thermal model by $η/n_c = e^{-m/T} < 1$, and this fact reduces any Bose-Einstein correction effects in the number and number fluctuation of pions. Fluctuations can be much larger than Poisson in the pion laser model and for a negative binomial description. The clan representation of the negative binomial distribution due to Van Hove and Giovannini is discussed using the present description. Applications to CERN/NA44 and CERN/NA49 data are discussed in terms of the relativistic hydrodynamic model.

nucl-th↗

arXiv1998

Predictions for sqrt{s} = 200 A*GeV Au+Au Collisions from Relativistic Hydrodynamics

The relativistic hydrodynamical model HYLANDER-C is used to give estimates for single inclusive particle momentum spectra in $\sqrt{s}$ = 200 $GeV/nucleon$ Au+Au collisions that will be investigated experimentally in the near future. The predictions are based on initial conditions that the initial fireball has a longitudinal extension of 1.6 $fm$ and an initial energy density of 30.8 $GeV/fm^3$ as obtained from a cascade model. For the collision energy considered here, different stopping scenarios are explored for the first time. Our calculations give particle yields of the order of 10,000 to 20,000 charged particles per event.

nucl-th↗

arXiv1997

Relativistic flows on a spacetime lattice

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 fluid flow. 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 fluid flow. A simple example is also explicitly studied, and some numerical results with figures are shown in the last section.

physics.flu-dyn↗

arXiv1997

The Equation of State of Nuclear Matter in Heavy Ion Collisions at CERN-SPS Energies from the Viewpoint of Relativistic Hydrodynamics

We present refits of single inclusive cross section data of mesons and baryons for central 158 $AGeV$ Pb+Pb collisions measured by the NA44 and NA49 Collaborations. In the theoretical approach we use the relativistic hydrodynamical code HYLANDER-C. We investigate several equations of state in their capability to describe the measured single inclusive momentum distributions. Based on the obtained fits we present results of the calculated Bose-Einstein correlation functions of identical pion pairs and discuss their features in comparison to measurements.

nucl-th↗

arXiv1997

On the Equation of State of Nuclear Matter in 158A GeV Pb+Pb Collisions

Within a hydrodynamical approach we investigate the sensitivity of single inclusive momentum spectra of hadrons in 158A GeV Pb+Pb collisions to three different equations of state of nuclear matter. Two of the equations of state are based on lattice QCD results and include a phase transition to a quark-gluon plasma. The third equation of state has been extracted from the microscopic transport code RQMD under the assumption of complete local thermalization. All three equations of state provide reasonable fits to data taken by the NA44 and NA49 Collaborations. The initial conditions before the evolution of the fireballs and the space-time evolution pictures differ dramatically for the three equations of state when the same freeze-out temperature is used in all calculations. However, the softest of the equations of state results in transverse mass spectra that are too steep in the central rapidity region. We conclude that the transverse particle momenta are determined by the effective softness of the equation of state during the fireball expansion.

nucl-th↗

arXiv1997

The Linear Correlation Coefficient vs. the Cross Term in Bose-Einstein Correlations

We investigate the nature of the new cross term for Gaussian parameterizations of Bose-Einstein correlations of identical particles emitted from purely chaotic hadron sources formed by relativistic heavy ion collisions. We find that this additional parameter in the so-called Bertsch parameterization can be expressed in terms of a linear ``out-longitudinal'' correlation coefficient for emission of bosons and two already known ``radius'' parameters, $R_l$ and $R_o$. The linear correlation coefficient is of kinematical nature and can be used to determine the widths of longitudinal momentum distributions.

nucl-th↗

arXiv1996

The Effects of Bose-Condensates on Single Inclusive Spectra and Bose-Einstein Correlations

The implications of the formation of a Bose condensate on one- and two-particle spectra are studied for ultrarelativistic nucleus-nucleus collisions in the framework of a hydrodynamic description. It is found that single particle spectra are considerably enhanced at low momenta. The Bose-Einstein correlation function has an intercept below two. For pion pairs in the central region a two-component structure may appear in the correlation function, which is different from that found in quantum optics. The chaoticity parameter is strongly momentum dependent.

nucl-th↗

arXiv1996

Hydrodynamical analysis of symmetric nucleus-nucleus collisions at CERN/SPS energies

We present a coherent theoretical study of ultrarelativistic heavy-ion data obtained at the CERN/SPS by the NA35/NA49 Collaborations using 3+1-dimensional relativistic hydrodynamics. We find excellent agreement with the rapidity spectra of negative hadrons and protons and with the correlation measurements in two experiments: $S+S$ at 200 $AGeV$ and $Pb+Pb$ at 160 $AGeV$ (preliminary results). Within our model this implies that for $Pb+Pb$ ($S+S$) a quark-gluon-plasma of initial volume 174 $fm^3$ (24 $fm^3$) with a lifetime 3.4 $fm/c$ (1.5 $fm/c$) was formed. It is found that the Bose-Einstein correlation measurements do not determine the maximal effective radii of the hadron sources because of the large contributions from resonance decay at small momenta. Also within this study we present an NA49 acceptance corrected two-pion Bose-Einstein correlation function in the invariant variable, $Q_{inv}$.

hep-ph↗

arXiv1995

Hydrodynamical analysis of single inclusive spectra and Bose-Einstein correlations for $Pb+Pb$ at 160 AGeV

We present the first analysis of preliminary data for $Pb+Pb$ at 160 $AGeV$ using 3+1-dimensional relativistic hydrodynamics. We find excellent agreement with the rapidity spectra of negative hadrons and the correlation measurements. The data indicates a large amount of stopping; $65\%$ of the invariant energy of the collision is thermalized and $73\%$ of the baryons are contained in the central fireball. Within our model this implies that a quark-gluon-plasma of lifetime 3.4 $fm/c$ was formed.

hep-ph↗

arXiv1993

Bose-condensation through resonance decay

We show that a system described by an equation of state which contains a high number of degrees of freedom (resonances) can create a considerable amount of superfluid (condensed) pions through the decay of short-lived resonances, if baryon number and entropy are large and the dense matter decouples from chemical equilibrium earlier than from thermal equilibrium. The system cools down faster in the presence of a condensate, an effect that may partially compensate the enhancement of the lifetime expected in the case of quark-gluon-plasma formation.

nucl-th↗