73697199
Elliptical flow and isospin effects in heavy-ion collisions at intermediate energies
The elliptical flow of fragments is studied for different systems at incident energies between 50 and 1000 MeV/nucleon using Isospin-dependent Quantum Molecular Dynamics (IQMD) Model. Our findings reveal that elliptical flow shows a transition from positive (in-plane) to negative (out-of-plane) value in the mid-rapidity region at certain incident energy, known as transition energy. This transition energy is found to depend on the model ingredients, size of the fragments, composite mass of the reacting system as well as on the impact parameter of the reaction. A reasonable agreement is observed for the excitation function of elliptical flow between the data and our calculations. Interestingly, the transition energy is found to exhibit a power law mass dependence.
118406564
Effect of the symmetry energy on nuclear stopping and its relation to the production of light charged fragments
We present a complete systematics (excitation function, impact parameter, system size, isospin asymmetry, and equations of state dependences) of global stopping and fragment production for heavy-ion reactions in the energy range between 50 and 1000 MeV/nucleon in the presence of symmetry energy and an isospin-dependent cross section. It is observed that the degree of stopping depends weakly on the symmetry energy and strongly on the isospin-dependent cross section. However, the symmetry energy and isospin-dependent cross section has an effect of the order of more than 10% on the emission of light charged particles (LCP's). It means that nuclear stopping and LCP's can be used as a tool to get the information of an isospin-dependent cross section. Interestingly, the LCP's emission in the presence of symmetry energy is found to be highly correlated with the global stopping.
117335698
Effect of isospin dependent cross-section on nuclear stopping
Nuclear stopping in heavy ion collisions (HIC) has been studied by means of rapidity distribution and asymmetry of nucleon momentum distribution. It is an important quantity in determining the outcome of a reaction. Fen Fu {\it et al.,} \cite{2} calculate both the radial flow and the degree of nuclear stopping in Pb + Pb and Ni + Ni at 0.4, 0.8 and 1.2 GeV/neucleon. They found that the expansion velocity as well as the degree of nuclear stopping are higher in the heavier system at all energies.
116891254
Production of light and intermediate mass fragments using various clusterization algorithms
For the present analysis we simulate the reaction 129Xe 54+197Au79 at E=50 MeV/nucleon respectively[3]. This reaction is simulated at different impact parameters using hard equation of state. The stored phase space is then analyzed by using MST, MSTP and MSTB algorithms. MSTB and MSTP identifies the free nucleons as early as possible. In the two cases, a check in the form of binding energy and momentum cut helps to identify the fragments quite early. The normal MST takes quite a long time to identify the stable fragments which are residual of excited fragments.
118085314
Rapidity distribution dependence of the transition energy in heavy-ion collisions
For the present analysis, simulations are carried out for thousand of events for the reaction of 79Au197 + 79Au197 at semi-central geometry using a hard equation of state. The whole of the analysis is performed for light charged particles (LCP's). The transition from in-plane to out-of-plane is observed only when the mid-rapidity region is included in the rapidity bin otherwise no transition is observed. The transition energy is found to be strongly dependent on the size of the rapidity bin. The transition energy is parameterized with a straight line interpolation.
119288476
Influence of charge asymmetry and isospin dependent cross-section on nuclear stopping
Using the isospin dependent quantum molecular dynamics model, we study the effect of charge asymmetry and isospin dependent cross-section on nuclear stopping and multiplicity of free nucleons and LMF’s. Simulations were carried out for the reactions 124 Xm + 124 Xm, where m varies from 47 to 59 and for 40 Yn+ 40 Yn, where n varies from 14 to 23. Our study shows that nuclear stopping as well as the production of LMF’s depend strongly on the isospin of the cross-section.
117647469
Non-Equilibrium Dynamics in a New Inflation Model and Cosmological Perturbations
15856484
Geometric construction of elliptic integrable systems and N=1* superpotentials
We show how the elliptic Calogero-Moser integrable systems arise from a symplectic quotient construction, generalising the construction for A_{N-1} by Gorsky and Nekrasov to other algebras. This clarifies the role of (twisted) affine Kac-Moody algebras in elliptic Calogero-Moser systems and allows for a natural geometric construction of Lax operators for these systems. We elaborate on the connection of the associated Hamiltonians to superpotentials for N=1* deformations of N=4 supersymmetric gauge theory, and argue how non-perturbative physics generates the elliptic superpotentials. We also discuss the relevance of these systems and the associated quotient construction to open problems in string theory. In an appendix, we use the theory of orbit algebras to show the systematics behind the folding procedures for these integrable models.
116887728
Sensitivity of elliptical flow in intermediate energy heavy-ion collisions
The detailed analysis of excitation function of elliptical flow by taking into account the nature of equation of state, nucleon-nucleon cross sections as well as momentum dependent interactions is performed within Quantum Molecular Dynamics (QMD)model. All the observables are found to sensitive towards the elliptical flow. The transition energy is found to be decrease with increase in the size of the fragment in the presence of static equation of state as well as with large cross sections, while, trend gets opposite when momentum dependent interactions are included. At last, the experimental data is verified with static hard equation of state in the presence of large cross sections.
16189897
PHENOMENOLOGICAL IMPLICATIONS OF A CLASS OF LEPTON MASS MATRICES
Phenomenological implications of a class of lepton mass matrices with parallel texture structure have been examined and phenomenologically interesting constraints on charged lepton and neutrino mass matrix parameters have been obtained.
15287891
Anomalous pseudoscalar-photon vertex in and out of equilibrium
The anomalous pseudoscalar-photon vertex is studied in real time in and out of equilibrium in a constituent quark model. The goal is to understand the in-medium modifications of this vertex, exploring the possibility of enhanced isospin breaking by electromagnetic effects as well as the formation of neutral pion condensates in a rapid chiral phase transition in peripheral, ultrarelativistic heavy-ion collisions. In equilibrium the effective vertex is afflicted by infrared and pinch singularities that require hard thermal loop and width corrections of the quark propagator. The resumed effective equilibrium vertex vanishes near the chiral transition in the chiral limit. In a strongly out of equilibrium chiral phase transition we find that the chiral condensate drastically modifies the quark propagators and the effective vertex. The ensuing dynamics for the neutral pion results in a potential enhancement of isospin breaking and the formation of {pi}{sup 0} condensates. While the anomaly equation and the axial Ward identity are not modified by the medium in or out of equilibrium, the effective real-time pseudoscalar-photon vertex is sensitive to low energy physics. (c) 2000 The American Physical Society.