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Creating high energy density in nuclei with energetic antiparticles

Description: The possibility of creating a phase change in nuclear matter using energetic antiprotons and antideuterons is examined. It is found that energy densities of the order of 2 GeV/c can be obtained for periods of approx.2 fm/c with the proper experimental selection of events. 10 refs., 7 figs.
Date: January 1, 1986
Creator: Gibbs, W.R.
Partner: UNT Libraries Government Documents Department

Effective temperatures in complete fusion for the system {sup 58}Ni + {sup 58}Ni at 500 MeV bombarding energy

Description: Triple coincidences between complex fragments with Z > 3, light charged particles and {gamma} transitions have been measured for the system {sup 58}Ni+{sup 58}Ni at 500 MeV incident energy. To this end the HILI detector and a 19 pack BaF{sub 2} cluster made of 19 crystals of TAPS geometry have been used. Effective temperatures have been obtained from the ratios of the bound excited level cross sections to the ground states ones for C. N and 0 evaporated after complete fusion of {sup 58}Ni +{sup 58}Ni at 500 MeV incident energy. The dependence of the effective temperature on the charged light particle multiplicity has been investigated.
Date: December 1, 1996
Creator: D`Onofrio, A.; Campajola, L.; Inglima, G. & Roca, V.
Partner: UNT Libraries Government Documents Department

Energy Spectra of Fragments from Silver and Uranium Bombarded with5.0 GeV Protons

Description: In this third paper in a series in which the characteristics of nuclear fragments produced in the interaction of 5 GeV protons with Ag and U targets were studied by means of dE/dx-E measurements with semiconductor detector telescopes new information was obtained on the energy spectra of light fragments. One set of measurements on fragments from a Ag target involved the use of a two-element telescope incorporating a {Delta}E detector as thin as 16 {micro}m. A new algorithm for processing the {Delta}E and E data to extract particle identification was developed and the resulting particle spectra showed superior resolution for the elements from Li(Z = 3) to S (Z = 16). Segments of the energy spectra of each of these elements were measured at 20{sup o} and, for many of them, also at 45{sup o}, 90{sup o}, 135{sup o} and 160{sup o} to the beam direction. By use of 3-element telescopes and absorbers the high energy part of the energy spectrum for isotopes of He, Li, Be, B, and C ejected from Ag and U targets was measured at 20{sup o}. The measurements extended beyond 300 MeV for {sup 6}Li and {sup 7}Li and to 400 MeV for {sup 7}Be. A distinct high-energy component was found in these cases. The suitability of nuclear evaporation as a description of the emission of the low-energy fragments was tested with two simple theoretical models, one specifying isotropic fragment emission from a moving nucleus at a fixed nuclear temperature and one specifying isotropic fragment emission from a set of moving nuclei with a Maxwellian distribution of excitation energies and forward momenta. The second could describe rather well all the 90{sup o} data, provided a Coulomb barrier 0.4 that of the classical tangent spheres barrier was used. However, the measured intensity in the forward direction ...
Date: August 1, 1972
Creator: Korteling, Ralph G.; Toren, C.R. & Hyde, Earl K.
Partner: UNT Libraries Government Documents Department

(Experimental physics at Yale University: Research proposal and budget Proposal, 1 January 1992--31 December 1996)

Description: This report reviews the following topics: nuclear and quark matter; correlated pairs from heavy ion collisions-search for new low mass resonances coupled to electron-positron collisions; proposed light ion research program; experimental nuclear astrophysics (explosive nucleosynthesis); search for rare decay modes and rare processes in nuclei; and nuclear spectroscopy at the extremes of spin, isospin, and temperature. (LSP).
Date: January 1, 1992
Partner: UNT Libraries Government Documents Department

[Experimental physics at Yale University: Research proposal and budget Proposal, 1 January 1992--31 December 1996]

Description: This report reviews the following topics: nuclear and quark matter; correlated pairs from heavy ion collisions-search for new low mass resonances coupled to electron-positron collisions; proposed light ion research program; experimental nuclear astrophysics (explosive nucleosynthesis); search for rare decay modes and rare processes in nuclei; and nuclear spectroscopy at the extremes of spin, isospin, and temperature. (LSP).
Date: July 1, 1992
Partner: UNT Libraries Government Documents Department

Finite-temperature corrections in the dilated chiral quark model

Description: We calculate the finite-temperature corrections in the dilated chiral quark model using the effective potential formalism. Assuming that the dilaton limit is applicable at some short length scale, we interpret the results to represent the behavior of hadrons in dense and hot matter. We obtain the scaling law, f{sub {pi}}(T)/f{sub {pi}} = m{sub Q}(T)/m{sub Q} {approx_equal} m{sub {sigma}}(T)/m{sub {sigma}}while we argue, using PCAC, that pion mass does not scale within the temperature range involved in our Lagrangian. It is found that the hadron masses and the pion decay constant drop faster with temperature in the dilated chiral quark model than in the conventional linear sigma model that does not take into account the QCD scale anomaly. We attribute the difference in scaling in heat bath to the effect of baryonic medium on thermal properties of the hadrons. Our finding would imply that the AGS experiments (dense and hot matter) and the RHIC experiments (hot and dilute matter) will ``see`` different hadron properties in the hadronization exit phase.
Date: March 1, 1995
Creator: Kim, Y.; Lee, Hyun Kyu & Rho, M.
Partner: UNT Libraries Government Documents Department

Hot nuclei -- Landau theory, thermal fluctuations and dissipation

Description: The basic ideas and theoretical methods used in the description of hot nuclei are reviewed. In particular, a macroscopic approach to shape transitions is discussed in the framework of the Landau theory in which the quadrupole shape degrees of freedom play the role of the order parameters. This theory describes the universal features of the nuclear shape evolution with temperature and spin. A unified description of fluctuations in all five quadrupole degrees of freedom is introduced and plays an important role in the calculation of physical observables. A macroscopic approach to the giant dipole resonance (GDR) in hot nuclei is developed. With all parameters fixed by the zero temperature nuclear properties, the theory predicts both the GDR cross-section and angular anisotropy of the {gamma}-rays in very good agreement with recent experiments. The intrinsic shape fluctuations are the main cause for the resonance broadening at higher temperatures, while the orientation fluctuations are responsible for the observed attenuation in the angular anisotropy. Dissipation at finite temperature is discussed in the framework of a Langevin-like equation describing the time-dependent shape fluctuations. Non-adiabatic effects may cause motional narrowing of the resonance.
Date: January 1, 1990
Creator: Alhassid, Y.
Partner: UNT Libraries Government Documents Department

Hot nuclei -- Landau theory, thermal fluctuations and dissipation

Description: The basic ideas and theoretical methods used in the description of hot nuclei are reviewed. In particular, a macroscopic approach to shape transitions is discussed in the framework of the Landau theory in which the quadrupole shape degrees of freedom play the role of the order parameters. This theory describes the universal features of the nuclear shape evolution with temperature and spin. A unified description of fluctuations in all five quadrupole degrees of freedom is introduced and plays an important role in the calculation of physical observables. A macroscopic approach to the giant dipole resonance (GDR) in hot nuclei is developed. With all parameters fixed by the zero temperature nuclear properties, the theory predicts both the GDR cross-section and angular anisotropy of the {gamma}-rays in very good agreement with recent experiments. The intrinsic shape fluctuations are the main cause for the resonance broadening at higher temperatures, while the orientation fluctuations are responsible for the observed attenuation in the angular anisotropy. Dissipation at finite temperature is discussed in the framework of a Langevin-like equation describing the time-dependent shape fluctuations. Non-adiabatic effects may cause motional narrowing of the resonance.
Date: December 31, 1990
Creator: Alhassid, Y.
Partner: UNT Libraries Government Documents Department

Initial State Temperature and Degrees of Freedom in SPS A+A Collisions

Description: A dramatic rise in the heat capacity <font face="symbol">e</font>T<sup>4</sup> of high-temperature nuclear/QGP matter has been a long-standing prediction in high-energy heavy-ion physics, but is difficult to verify directly. Initial-state energy densities, measured through calorimetery, and limits on initial-state temperature, inferred through measurement of high-P<sub>T</sub> direct photons, can be combined to provide a nearly model-independent lower limit on the beat capacity of initial-state matter in A+A collisions at the CERN-SPS. This is the most direct evidence to date for the rise in the heat capacity, and the implied new degrees of freedon, in high-temperature nuclear matter.
Date: March 20, 1999
Creator: Stankus, P.
Partner: UNT Libraries Government Documents Department

Interactions of 100 MeV/nucleon /sup 40/Ar with uranium

Description: Fragments produced in the interactions of 100 MeV/nucleon /sup 40/Ar projectiles with a uranium target were measured at energies from 10 to 130 MeV/nucleon at angles from 10 to 170/sup 0/. Nuclei with charge 5 less than or equal to Z less than or equal to 10 were observed. The data can roughly be divided into two groups, corresponding to central and pripheral collisions. The central collision data can be fit with a thermal model that uses two recoiling sources. The source velocities are consistent with predictions of the fireball and target explosion models, but the source temperatures inferred from the data are higher than one would expect on the basis of energy and momentum conservation. These results are similar to those obtained in previous studies at beam energies of 400 and 500 MeV/nucleon. The data also follow the pattern of a universal curve of invariant cross section vs momentum. The projectile fragmentation data are also fit by two thermal sources. There are indications that the observed temperatures are higher than one would expect on the basis of other projectile fragmentation studies. The projectile fragmentation data are studied in terms of a simple friction model. Order-of-magnitude estimates show that the data may be consistent with the model, but further development, calculation, and experimentation are necessary to check the validity of the model at this beam energy. A preliminary investigation is made of the possibility that the projectile may pick up one or more target nucleons before it fragments. This process leads to widening of the distributions at large momentum transfers. Much of the spectrum can be described by falling exponentials in energy in the emitting frames. It is concluded that the observed spectrum is due to nonthermal sources as the temperatures derived from the slopes of the exponentials are greater ...
Date: December 1, 1979
Creator: Frankel, K.A.
Partner: UNT Libraries Government Documents Department

Light-particle emission as a probe of dissipation and deexcitation mechanisms in heavy-ion reactions. [Approximately 8. 5 MeV/nucl]

Description: The relevance of studies of light-particle emission associated with damped nuclear reactions for investigating properties of the reaction mechanism, in particular of the energy dissipation mechanism, is discussed. Processes of instantaneous particle emission are reviewed, as related to heavy-ion reactions. Methods are outlined concerning information on the conditions of the intermediate nuclear system at scission revealed in the processes of statistical particle evaporation from the reaction fragments. They are employed in studies of neutron emission in the damped reactions /sup 165/Ho+/sup 56/Fe and /sup 165/Ho+/sup 136/Xe, yielding evidence for a rapid thermalization and a relaxation of the mass-to-charge asymmetry of the system. Progress is reported for attempts to achieve a unified description of energy dissipation, nucleon exchange, and particle emission in damped nuclear reactions. 19 figures, 1 table.
Date: December 1, 1979
Creator: Schroeder, W.U.
Partner: UNT Libraries Government Documents Department

Physics at RHIC (Relativistic Heavy Ion Collider): What do we want to know, and what do we want to measure

Description: The main features of nuclear collisions that are to be measured at the Relativistic Heavy Ion Collider (RHIC) are briefly surveyed. The main questions to be addressed in studying such collisions are stated, along with some possible experimental ways of addressing these questions. The features of relativistic heavy ion collisions discussed are: macroscopic size and collective behavior, energy density, thermal equilibrium, initial temperature, chemical equilibrium, color deconfinement, and plasma expansion and hadronization. (LEW)
Date: January 1, 1987
Creator: Satz, H.
Partner: UNT Libraries Government Documents Department

Reaction mechanisms and production of exotic nuclei using 200 MeV/n /sup 40/Ar. [213 and 205 MeV, cross sections, yields]

Description: In order to study the reaction mechanism, carbon and thorium targets were bombarded by 213 MeV/n /sup 40/Ar ions. Energy spectra were measured at 0 to 4/sup 0/. The /sup 34/S energy spectrum distribution widths can be related to the nuclear temperature giving a value of 9.6 + 1.1 MeV. The measured isotope production cross sections for the carbon target are also given. The yields of very neutron-rich nuclei resulting from the fragmentation of /sup 40/Ar at 205 MeV/n were also measured, and the projected spectra are discussed. 2 references. (JFP)
Date: January 1, 1979
Creator: Westfall, G.D.
Partner: UNT Libraries Government Documents Department

Stochastic resonance in a periodically modulated dissipative nuclear dynamics

Description: A fission decay of highly excited periodically driven compound nuclei is considered in the framework of Langevin approach. The authors have used residual-time distribution (RTD) as the tool for studying of dynamic features in a presence of periodic perturbation. The structure of RTD essentially depends on the relation between Kramers decay rate and the frequency {omega} of the periodic perturbation. In particular, intensity of the first peak in RTD has a sharp maximum at certain nuclear temperature depending on {omega}. This maximum should be considered as first-hand manifestation of stochastic resonance in nuclear dynamics.
Date: February 1, 2001
Creator: Berezovoy, V.P.
Partner: UNT Libraries Government Documents Department

Superdeformed nuclei: Shells-vs-liquid drop, pairing-vs-thermal excitations, triaxial-vs-octupole shapes, super-superdeformation

Description: Mechanisms influencing the behavior of superdeformed nuclei are studied using several well established nuclear structure techniques. In particular: pairing, thermal excitation, shell and liquid-drop mechanisms are considered. The effects of quadrupole and hexadecapole (both axial and non-axial), and octupole deformation degrees of freedom are studied. Most of the results are illustrated using the case of /sup 152/Dy nucleus in which a superdeformed band extending up to I approx. 60 h-bar has been found in experiment. Some comparisons between /sup 152/Dy and the nuclei in the neighborhood are given. Calculations show that pairing ''de-aligns'' typically 6 to 8 units of angular momentum, as compared to the corresponding rigid rotation. This takes place for spins extending up to the highest limit, and thus diminishes the effective moments of inertia. Predicted octupole shape susceptibility is extremely large, significantly stronger than the susceptibilities known in the ground-states of many Actinide nuclei. Consequences of this result for the near-constancy of the dynamical moments of inertia are pointed out. Nuclear level densities calculated in function of spin, excitation energy and deformation explain the ''unusual'' side feeding pattern of the /sup 152/Dy superdeformed states. Predictions of super-superdeformed nuclear states (axis ratio varying between 2:1 and 3:1 or more) are given and exemplified for Erbium nuclei. Finally, the problem of superdeformation stability and the influence of increased collective inertia on a barrier penetration are examined. An analytical expression for the effective inertia parameter is obtained and its derivation outlined. 35 refs., 9 figs.
Date: January 1, 1987
Creator: Dudek, J.
Partner: UNT Libraries Government Documents Department