Dynamical Features Of Nuclei And Finite Fermi Systems - Proceedings Of The International Workshop

Dynamical Features Of Nuclei And Finite Fermi Systems - Proceedings Of The International Workshop
Author: X Vinas
Publisher: World Scientific
Total Pages: 522
Release: 1994-07-05
Genre:
ISBN: 9814552402

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These proceedings address the new emerging questions in nuclear dynamics such as fluctuations, nuclear multifragmentation, transport theories and particle production in heavy-ion reactions. Parts of the proceedings are also devoted to the physics of metallic and atomic clusters where, quite often, nuclear concepts and techniques are applied.

Measurement of Non-flow Correlations and Elliptic Flow Fluctuations in Au+Au Collisions at Relativistic Heavy Ion Collider

Measurement of Non-flow Correlations and Elliptic Flow Fluctuations in Au+Au Collisions at Relativistic Heavy Ion Collider
Author: Burak Han Alver
Publisher:
Total Pages: 108
Release: 2010
Genre:
ISBN:

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Measurements of collective flow and two-particle correlations have proven to be effective tools for understanding the properties of the system produced in ultrarelativistic nucleus-nucleus collisions at the Relativistic Heavy Ion Collider (RHIC). Accurate modeling of the initial conditions of a heavy ion collision is crucial in the interpretation of these results. The anisotropic shape of the initial geometry of heavy ion collisions with finite impact parameter leads to an anisotropic particle production in the azimuthal direction through collective flow of the produced medium. In "head-on" collisions of Copper nuclei at ultrarelativistic energies, the magnitude of this "elliptic flow" has been observed to be significantly large. This is understood to be due to fluctuations in the initial geometry which leads to a significant anisotropy even for most central Cu+Cu collisions. This thesis presents a phenomenological study of the effect of initial geometry fluctuations on two-particle correlations and an experimental measurement of the magnitude of elliptic flow fluctuations which is predicted to be large if initial geometry fluctuations are present. Two-particle correlation measurements in Au+Au collisions at the top RHIC energies have shown that after correction for contributions from elliptic flow, strong azimuthal correlation signals are present at A0 = 0 and A0 ~ 120. These correlation structures may be understood in terms of event-by-event fluctuations which result in a triangular anisotropy in the initial collision geometry of heavy ion collisions, which in turn leads to a triangular anisotropy in particle production. It is observed that similar correlation structures are observed in A Multi-Phase Transport (AMPT) model and are, indeed, found to be driven by the triangular anisotropy in the initial collision geometry. Therefore "triangular flow" may be the appropriate description of these correlation structures in data. The measurement of elliptic flow fluctuations is complicated by the contributions of statistical fluctuations and other two-particle correlations (non-flow correlations) to the observed fluctuations in azimuthal particle anisotropy. New experimental techniques, which crucially rely on the uniquely large coverage of the PHOBOS detector at RHIC, are developed to quantify and correct for these contributions. Relative elliptic flow fluctuations of approximately 30-40% are observed in 6-45% most central Au+Au collisions at s NN= 200 GeV. These results are consistent with the predicted initial geometry fluctuations.

Momentum-integrated Elliptic Flow and Transverse Collision Geometry in Ultrarelativistic Nucleus-nucleus Collisions

Momentum-integrated Elliptic Flow and Transverse Collision Geometry in Ultrarelativistic Nucleus-nucleus Collisions
Author: Peter Kirk Walters
Publisher:
Total Pages: 164
Release: 2013
Genre:
ISBN:

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"Ultrareletivistic nuclear collisions at the Relativistic Heavy-Ion Collider have produced a high temperature, high energy density medium consisting of a strongly interacting plasma of quarks and gluons. This extreme state of matter provides a testing ground for quantum chromodynamics. Previous studies of gold-gold collisions over a wide range of beam energies revealed many properties of the produced medium. However, these studies were restricted to relatively large colliding systems which resulted in large collision volumes; it is therefore important to investigate what role the size of the collision volume plays in the evolution of the source, particularly as the source volume becomes vanishingly small. This can be achieved with symmetric copper-copper collisions, which offer access to a range of system sizes from [approximately] 10 participating nucleons up through volumes comparable to those created in gold-gold collisions. Collective behaviors of the produced particles in heavy-ion collisions can provide useful probes into the state of the medium produced, including its degree of thermalization and its properties. The elliptic flow, an anisotropy in the azimuthal distribution of the produced particles that is strongly correlated to the initial transverse geometry of the colliding nuclei, is one such collective motion that has proven to be a very useful observable for studying heavy-ion collisions. This is because it exhibits fairly large magnitudes in the systems being studied and is sensitive to the strength of the partonic interactions in-medium. The PHOBOS experiment, which can measure the positions of produced charged particles with high precision over nearly the full solid angle, is well-suited to study the elliptic flow and its evolution over an extended range along the beam direction. The elliptic flow from copper-copper collisions at center-of-mass energies of 22.4, 62.4, and 200GeV per nucleon pair are presented as a function of pseudorapidity and system size. The appearance of unexpected behaviors in the smaller system prompted a re-examination of the role of the collision geometry on the production of elliptic flow. Studies using Monte-Carlo Glauber simulations found that the fluctuating spatial configurations of the component nucleons in the colliding nuclei could result in significant variation of the shape of the nuclear overlap on an event-by-event basis, and that these fluctuations become important for small systems. The eccentricity, a quantity that characterizes the ellipticity of the nuclear overlap in the transverse plane, is redefined to account for these fluctuations as the participant eccentricity. It is found that the event-by-event fluctuations of the participant eccentricity are able to fully account for the observed elliptic flow in the smaller system. The participant eccentricity is used to normalize the measured elliptic flow across different colliding systems to a common initial geometry so that a direct comparison of the properties of the produced medium can be made. It is found that the produced medium evolves smoothly from systems of [approximately] 10 participant nucleons to systems involving more than 350 nucleons and for collision energies from 19.6 to 200GeV per nucleon pair. This smooth evolution of the elliptic flow is also observed as a function of pseudorapidity in all the systems studied. After accounting for the initial geometry, no indication of the identity of the original colliding system is observed"--Page vi-vii.

INIS Atomindex

INIS Atomindex
Author:
Publisher:
Total Pages: 682
Release: 1995
Genre: Nuclear energy
ISBN:

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Energy Research Abstracts

Energy Research Abstracts
Author:
Publisher:
Total Pages: 1284
Release: 1987
Genre: Power resources
ISBN:

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Equilibration, Compression and Flow at the Bevalac

Equilibration, Compression and Flow at the Bevalac
Author:
Publisher:
Total Pages:
Release: 1984
Genre:
ISBN:

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This paper presents data acquired in the past two years by the Streamer Chamber group and the Plastic Ball group. The paper presents evidence that at Bevalac energies, head-on nuclear collisions result in stopping; it presents evidence for collective flow of the interacting nuclei; it presents evidence that a substantial part of the energy is tied up in compressional energy at the high density phase of the collision; finally, it presents recent data concerning aspects of the collisions such as interaction volume, particle ratios and temperatures. At the meeting at Bielefeld two years ago, it was not possible to make definitive statements about most of these subjects: the progress in the intervening period has been remarkable. 17 references, 14 figures, 1 table.