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Isospin Effect on the Process of Multifragmentation and Dissipation at Intermediate Energy Heavy Ion Collisions  [PDF]
Jian-Ye Liu,Yan-Fang Yang,Wei Zuo,Shun-Jin Wang,Qiang Zhao,Wen-Jun Guo,Bo Chen
Physics , 2001, DOI: 10.1103/PhysRevC.63.054612
Abstract: In the simulation of intermediate energy heavy ion collisions by using the isospin dependent quantum molecular dynamics, the isospin effect on the process of multifragmentation and dissipation has been studied. It is found that the multiplicity of intermediate mass fragments $N_{imf}$ for the neutron-poor colliding system is always larger than that for the neutron-rich system, while the quadrupole of single particle momentum distribution $Q_{zz}$ for the neutron-poor colliding system is smaller than that of the neutron-rich system for all projectile-target combinations studied at the beam energies from about 50MeV/nucleon to 150MeV/nucleon. Since $Q_{zz}$ depends strongly on isospin dependence of in-medium nucleon-nucleon cross section and weakly on symmetry potential at the above beam energies, it may serve as a good probe to extract the information on the in-medium nucleon-nucleon cross section. The correlation between the multiplicity $N_{imf}$ of intermediate mass fragments and the total numer of charged particles $N_c$ has the behavior similar to $Q_{zz}$, which can be used as a complementary probe to the in-medium nucleon-nucleon cross section.
Reaction Dynamics and Multifragmentation in Fermi Energy Heavy Ion Reactions  [PDF]
R. Wada,T. Keutgen,K. Hagel,Y. G. Ma,J. Wang,M. Murray,L. Qin,P. Smith,J. B. Natowitz,R. Alfarro,J. Cibor,M. Cinausero,Y. El Masri,D. Fabris,E. Fioretto,A. Keksis,M. Lunardon,A. Makeev,N. Marie,E. Martin,A. Martinez-Davalos,A. Menchaca-Rocha,G. Nebbia,G. Prete,V. Rizzi,A. Ruangma,D. V. Shetty,G. Souliotis,P. Staszel,M. Veselsky,G. Viesti,E. M. Winchester,S. J. Yennello,Z. Majka,A. Ono
Physics , 2003, DOI: 10.1103/PhysRevC.69.044610
Abstract: The reaction systems, 64Zn + 58Ni, 64Zn + 92Mo, 64Zn + 197Au, at 26A, 35A and 47A MeV, have been studied both in experiments with a 4$\pi$ detector array, NIMROD, and with Antisymmetrized Molecular Dynamics model calculations employing effective interactions corresponding to soft and stiff equations of state (EOS). Direct experimental observables, such as multiplicity distributions, charge distributions, energy spectra and velocity spectra, have been compared in detail with those of the calculations and a reasonable agreement is obtained. The velocity distributions of $\alpha$ particles and fragments with Z >= 3 show distinct differences in calculations with the soft EOS and the stiff EOS. The velocity distributions of $\alpha$ particle and Intermediate Mass Fragments (IMF's) are best described by the stiff EOS. Neither of the above direct observables nor the strength of the elliptic flow are sensitive to changes in the in-medium nucleon-nucleon (NN) cross sections. A detailed analysis of the central collision events calculated with the stiff EOS revealed that multifragmentation with cold fragment emission is a common feature predicted for all reactions studied here. A possible multifragmentation scenario is presented; after the preequilibrium emission ceases in the composite system, cold light fragments are formed in a hotter gas of nucleons and stay cold until the composite system underdoes multifragmentation. For reaction with 197Au at 47A MeV a significant radial expansion takes place. For reactions with 58Ni and 92Mo at 47A MeV semi-transparency becomes prominent. The differing reaction dynamics drastically change the kinematic characteristics of emitted fragments. This scenario gives consistent explanations for many existing experimental results in the Fermi energy domain.
The study of multifragmentation around transition energy in intermediate energy heavy-ion collisions  [PDF]
Karan Singh Vinayak,Suneel Kumar
Physics , 2011, DOI: 10.1103/PhysRevC.83.034614
Abstract: Fragmentation of light charged particles is studied for various systems at different incident energies between 50 and 1000 MeV/nucleon. We analyze fragment production at incident energies above, below and at transition energies using the isospin dependent quantum molecular dynamics(IQMD) model. The trends observed for the fragment production and rapidity distributions depend upon the incident energy, size of the fragments, composite mass of the reacting system as well as on the impact parameter of the reaction. The free nucleons and light charged particles show continous homogeneous changes irrespective of the transition energies indicating that there is no relation between the transition energy and production of the free as well as light charged particles.
Multifragmentation and Symmetry Energy Studied with AMD  [PDF]
Akira Ono
Physics , 2006, DOI: 10.1063/1.2710595
Abstract: The antisymmetrized molecular dynamics (AMD) simulations suggest that the isospin composition of fragments produced dynamically in multifragmentation reactions is basically governed by the symmetry energy of low-density uniform nuclear matter rather than the symmetry energy for the ground-state finite nuclei. After the statistical secondary decay of the excited fragments, the symmetry energy effect still remains in the fragment isospin composition, though the effect in the isoscaling parameter seems a very delicate problem.
Photon statistics and dynamics of Fluorescence Resonance Energy Transfer  [PDF]
Andrew J. Berglund,Andrew C. Doherty,Hideo Mabuchi
Physics , 2002, DOI: 10.1103/PhysRevLett.89.068101
Abstract: We report high time-resolution measurements of photon statistics from pairs of dye molecules coupled by fluorescence resonance energy transfer (FRET). In addition to quantum-optical photon antibunching, we observe photon bunching on a timescale of several nanoseconds. We show by numerical simulation that configuration fluctuations in the coupled fluorophore system could account for minor deviations of our data from predictions of basic Forster theory. With further characterization we believe that FRET photon statistics could provide a unique tool for studying DNA mechanics on timescales from 10^-9 to 10^-3 s.
Dynamical effects in multifragmentation at intermediate energies  [PDF]
J. Colin,D. Cussol,J. Normand,N. Bellaize,B. Borderie,R. Bougault,B. Bouriquet,A. M. Buta,J. L. Charvet,A. Chbihi,R. Dayras,D. Durand,J. D. Frankland,E. Galichet,D. Guinet,B. Guiot,S. Hudan,P. Lautesse,F. Lavaud,N. Le Neindre,O. Lopez,L. Manduci,J. Marie,L. Nalpas,M. Parlog,P. Pawlowski,E. Plagnol,M. F. Rivet,E. Rosato,R. Roy,J. C. Steckmeyer,B. Tamain,A. Van Lauwe,E. Vient,M. Vigilante,C. Volant,J. P. Wieleczko
Physics , 2003, DOI: 10.1103/PhysRevC.67.064603
Abstract: The fragmentation of the quasi-projectile is studied with the INDRA multidetector for different colliding systems and incident energies in the Fermi energy range. Different experimental observations show that a large part of the fragmentation is not compatible with the statistical fragmentation of a fully equilibrated nucleus. The study of internal correlations is a powerful tool, especially to evidence entrance channel effects. These effects have to be included in the theoretical descriptions of nuclear multifragmentation.
Non-Linear Mean Field Dynamics in the Nuclear Spinodal Zone  [PDF]
G. F. Burgio,M. Baldo,A. Rapisarda
Physics , 1993, DOI: 10.1016/0370-2693(94)90247-X
Abstract: We demonstrate, by numerical simulations, that the dynamics of nuclear matter mean field inside the spinodal region is chaotic. Spontaneous symmetry-breaking - no explicit fluctuating term is considered - occurs leading to wild unpredictable density fluctuations. A proper recipe to calculate an average Lyapunov exponent in this multidimensional phase space is introduced. The latter is calculated for different values of the density in order to characterize in a quantitative way the chaotic and regular regions. It is argued that the mean field chaoticity can be the main mechanism of the nuclear multifragmentation occurring in the intermediate energy reactions.
Dynamics of Logamediate and Intermediate Scenarios in the Dark Energy Filled Universe  [PDF]
Piyali Bagchi Khatua,Ujjal Debnath
Physics , 2010, DOI: 10.1007/s10773-010-0617-6
Abstract: We have considered a model of two component mixture i.e., mixture of Chaplygin gas and barotropic fluid with tachyonic field. In the case, when they have no interaction then both of them retain their own properties. Let us consider an energy flow between barotropic and tachyonic fluids. In both the cases we find the exact solutions for the tachyonic field and the tachyonic potential and show that the tachyonic potential follows the asymptotic behavior. We have considered an interaction between these two fluids by introducing a coupling term. Finally, we have considered a model of three component mixture i.e., mixture of tachyonic field, Chaplygin gas and barotropic fluid with or without interaction. The coupling functions decays with time indicating a strong energy flow at the initial period and weak stable interaction at later stage. To keep the observational support of recent acceleration we have considered two particular forms (i) Logamediate Scenario and (ii) Intermediate Scenario, of evolution of the Universe. We have examined the natures of the recent developed statefinder parameters and slow-roll parameters in both scenarios with and without interactions in whole evolution of the universe.
Modification of surface energy in nuclear multifragmentation  [PDF]
A. S. Botvina,N. Buyukcizmeci,M. Erdogan,J. Lukasik,I. N. Mishustin,R. Ogul,W. Trautmann
Physics , 2006, DOI: 10.1103/PhysRevC.74.044609
Abstract: Within the statistical multifragmentation model we study modifications of the surface and symmetry energy of primary fragments in the freeze-out volume. The ALADIN experimental data on multifragmentation obtained in reactions induced by high-energy projectiles with different neutron richness are analyzed. We have extracted the isospin dependence of the surface energy coefficient at different degrees of fragmentation. We conclude that the surface energy of hot fragments produced in multifragmentation reactions differs from the values extracted for isolated nuclei at low excitation. At high fragment multiplicity, it becomes nearly independent of the neutron content of the fragments.
Ratio of shear viscosity to entropy density in multifragmentation of Au + Au  [PDF]
C. L. Zhou,Y. G. Ma,D. Q. Fang,S. X. Li,G. Q. Zhang
Physics , 2012, DOI: 10.1209/0295-5075/98/66003
Abstract: The ratio of the shear viscosity ($\eta$) to entropy density ($s$) for the intermediate energy heavy-ion collisions has been calculated by using the Green-Kubo method in the framework of the quantum molecular dynamics model. The theoretical curve of $\eta/s$ as a function of the incident energy for the head-on Au+Au collisions displays that a minimum region of $\eta/s$ has been approached at higher incident energies, where the minimum $\eta/s$ value is about 7 times Kovtun-Son- Starinets (KSS) bound (1/4$\pi$). We argue that the onset of minimum $\eta/s$ region at higher incident energies corresponds to the nuclear liquid gas phase transition in nuclear multifragmentation.
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