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Nuclear matter phase diagram from compound nucleus decay  [cached]
Moretto L.G.,Elliott J.B.,Lake P.T.,Phair L.
EPJ Web of Conferences , 2012, DOI: 10.1051/epjconf/20122108009
Abstract: The finite size of nuclei and the Coulomb interaction make it difficult to describe systems interacting through the strong force into thermodynamic terms. Our task is to extract the phase diagram of the theoretical infinite symmetrical uncharged nuclear matter from experiments of nuclear collisions where the systems are neither infinite, symmetrical, nor uncharged. Decay yields from such experiments are translated into coexistence densities and pressures by use of Fisher's droplet model. This method is tested on model systems such as the Ising model and a system of particles interacting via the Lennard-Jones potential. The specific problems inherent to nuclear reactions are considered. These include finite size effects, Coulomb repulsion, and the lack of a physical vapor in contact with a decaying system. Experimental data of compound nucleus experiments are studied within this framework, which is also shown to extend to higher energy reactions. Finally, the phase diagram of nuclear matter is extracted.
Coulomb energy of axially deformed nucleus  [PDF]
Ning Wang,Xuexin Yu,Min Liu
Physics , 2010, DOI: 10.1142/S0217732311034487
Abstract: We previously proposed a formula for calculating the Coulomb energy of spherical nucleus with Wood-Saxon charge distribution. In this work, the analytical formula is extended for description of the Coulomb energy of nucleus with beta2 deformation.
Geometry of the Vapor Liquid Coexistence in the Gibbs Space  [PDF]
Eduardo Pi?a
Physics , 2011,
Abstract: The phase coexistence is illuminated with geometric views of the thermodynamic variables, according to Gibbs' choices. Quantities and relations between them are obtained. The existence of the edge of regression with tangents coincident with the straight lines connecting the coexistence points of phase equilibrium is stressed. A geometric approach to the critical point leads to estimation of the values of the critical exponents for the angles formed by the coexistence curve and the straight lines with the principal direction along the minimal curvature.
Energy dependence of nucleus-nucleus potential close to the Coulomb barrier  [PDF]
Kouhei Washiyama,Denis Lacroix
Physics , 2008, DOI: 10.1103/PhysRevC.78.024610
Abstract: The nucleus-nucleus interaction potentials in heavy-ion fusion reactions are extracted from the microscopic time-dependent Hartree-Fock theory for mass symmetric reactions $^{16}$O${}+^{16}$O, $^{40}$Ca${}+^{40}$Ca, $^{48}$Ca${}+^{48}$Ca and mass asymmetric reactions $^{16}$O$ +^{40,48}$Ca, $^{40}$Ca${}+^{48}$Ca, $^{16}$O+$^{208}$Pb, $^{40}$Ca+$^{90}$Zr. When the center-of-mass energy is much higher than the Coulomb barrier energy, potentials deduced with the microscopic theory identify with the frozen density approximation. As the center-of-mass energy decreases and approaches the Coulomb barrier, potentials become energy dependent. This dependence signs dynamical reorganization of internal degrees of freedom and leads to a reduction of the "apparent" barrier felt by the two nuclei during fusion of the order of $2-3 %$ compared to the frozen density case. Several examples illustrate that the potential landscape changes rapidly when the center-of-mass energy is in the vicinity of the Coulomb barrier energy. The energy dependence is expected to have a significant role on fusion around the Coulomb barrier.
Aspects of Coulomb Dissociation and Interference in Peripheral Nucleus-Nucleus Collisions  [PDF]
Joakim Nystrand,Anthony J. Baltz,Spencer R. Klein
Physics , 2002,
Abstract: Coherent vector meson production in peripheral nucleus-nucleus collisions is discussed. These interactions may occur for impact parameters much larger than the sum of the nuclear radii. Since the vector meson production is always localized to one of the nuclei, the system acts as a two-source interferometer in the transverse plane. By tagging the outgoing nuclei for Coulomb dissociation it is possible to obtain a measure of the impact parameter and thus the source separation in the interferometer. This is of particular interest since the life-time of the vector mesons are generally much shorter than the impact parameters of the collisions.
Liquid-vapor coexistence in square-well fluids: an RHNC study  [PDF]
Achille Giacometti,Giorgio Pastore,Fred Lado
Physics , 2009, DOI: 10.1080/00268970902889642
Abstract: We investigate the ability of the reference hypernetted-chain integral equation to describe the phase diagram of square-well fluids with four different ranges of attraction. Comparison of our results with simulation data shows that the theory is able to reproduce with fairly good accuracy a significant part of the coexistence curve, provided an extrapolation procedure is used to circumvent the well-known pathologies of the pseudo-spinodal line, which are more severe at reduced width of the attractive well. The method provides a useful approach for a quick assessment of the location of the liquid-vapor coexistence curve in this kind of fluid and serves as a check for the more complex problem of anisotropic "patchy" square-well molecules.
Coulomb Sums and Modification of Nucleons in The Atomic Nucleus  [PDF]
A. Yu. Buki
Physics , 2012,
Abstract: Experimental values of Coulomb sums for q > 2 fm^(-1) are considered. Assuming that a part of nucleons is modified in the nucleus, an approach is offered, in the framework of which the calculation is in agreement with the experimental data. It gives the nuclear matter density value, above which the nucleon changes its properties. The radius of a modified proton is estimated, the possibilities for a further investigation into its properties are discussed.
Multiple shape coexistence in the nucleus $^{80}$Zr  [PDF]
Tomás R. Rodríguez,J. Luis Egido
Physics , 2011, DOI: 10.1016/j.physletb.2011.10.003
Abstract: We study the low-lying energy spectrum of the rp-process waiting point nucleus 80Zr with state-of-the-art beyond mean field methods with the Gogny D1S interaction. Symmetry restoration and configuration mixing of axial and triaxial shapes are included in the calculations. Five 0+ states corresponding to different nuclear shapes are obtained below 2.25 MeV and several rotational and {\gamma}- bands built upon them are identified. Nevertheless, these states do not modify the {\beta}-decay half-life having a negligible effect in the rp-process. A good agreement with the available experimental data is obtained.
Primakoff production of $π^0$, $η$ and $η'$ in the Coulomb field of a nucleus  [PDF]
Murat M. Kaskulov,Ulrich Mosel
Physics , 2011, DOI: 10.1103/PhysRevC.84.065206
Abstract: Photoproduction of neutral pseudoscalar mesons $\pi^0,\eta(547)$ and $\eta'(958)$ in the Coulomb field of an atomic nucleus is studied using a model which describes the Primakoff and nuclear parts of the production amplitude. At high energies the nuclear background is dominated by the exchange of $C$-parity odd Regge trajectories. In the coherent production the isospin filtering makes the $\omega(782)$ a dominant trajectory. The calculations are in agreement with $\pi^0$ data from JLAB provided the photon shadowing and final state interactions of mesons are taken into account. The kinematic conditions which allow to study the Primakoff effect in $\eta$ and $\eta'$ photoproduction off nuclei are further discussed. We also give predictions for the higher energies available at the JLAB upgrade.
Asymmetry of the vapor-liquid coexistence curve: the asymptotic behavior of the "diameter"  [PDF]
M. Ya. Sushko,O. M. Babiy
Physics , 2009,
Abstract: We analyze, without resort to any model field-mixing scheme, the leading temperature-dependent term in the "diameter" of the coexistence curve asymptotically close to the vapor-liquid critical point. For this purpose, we use a simple non-parametric equation of state which we develop by meeting several general requirements. Namely, we require that the desired equation (1) lead to correct asymptotic behavior for a limited number of the fluid's parameters along selected thermodynamic paths, (2) reveal a Van der Waals loop below the critical point, and (3) be consistent with a rigorous definition of the isothermal compressibility in the critical region. For the temperature interval in question, the proposed equation approximates experimental data with an accuracy comparable to those given by Schofield's parametric equation and by other authors' equations. The desired term is obtained by applying the Maxwell rule to the equation and can be represented as D_{2 \beta} | \tau |^{2 \beta}, where | \tau | = | T - T_{c} | / T_{c}, and \beta is the critical exponent for the order parameter. The amplitude D_{2 \beta} is determined explicitly for the volume-temperature and entropy-temperature planes.
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