62827271
To Study the effects of isospin cross section on mass asymmetric nuclear reactions
We studied the effect of cross section on mass asymmetric systems. The mass asymmetry of a reaction can be defined by the asymmetry parameter {\eta} = |(AT - AP)/(AT + AP)|; [1] where AT and AP are the masses of the target and projectile, respectively. The {\eta} = 0 corresponds to the symmetric reactions, whereas non-zero values of {\eta} define different asymmetries of a reaction. Reactions include 208Pb82 + 208Pb82 having {\eta} = 0, 40Ca20 + 208Pb82 having {\eta} = 0.6 and 12C6 + 197Au79 having {\eta} = 0.8 This work has been carried out within the frame work of isospin dependent quantum molecular dynamics (IQMD) model.
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.
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.
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.
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.
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.
118403162
αdecay chains study for the recently observed superheavy elementZ=117within the isospin cluster model
The recently observed $\alpha$-decay chains $^{293-294}117$ were produced by the fusion reactions with target $^{249}Bk$ and projectile $^{48}Ca$ at Dubna in Russia. The reported cross-sections for the mentioned reaction are $\sigma=0.5(+1.1,-0.4)$pb and $\sigma$=1.3(+1.5,-0.6)$pb$ at $E^{*}=35MeV$ and $E^{*}=39MeV$, respectively. The Q-values of $\alpha$-decay and the half-lives $Log_{10}T^{\alpha}_{1/2}$(s) are calculated for the $\alpha$-decay chains of $^{293-294}117$ nuclei, within the framework of Isospin Cluster Model (ICM). In the ICM model the proximity energy is improved by using the isospin dependent radius of parent, daughter and alpha particle. The binding energy $B(A_{i}, Z_{i})$ (i=1,2) of any nucleus of mass number A and atomic number Z was obtained from a phenomenological and more genaralized BW formula given by \cite{samanta02}. The calculated results in ICM are compared with the experimental results and other theoretical Macro-Microscopic(M-M), RMF(with NL3 and SFU Gold forces parameter) model calculations. The estimated values of $\alpha$-decay half-lives are in good agreement with the recent data. The ICM calculation is in favor of the persence of magic number at N=172.
122105491
Charge-current commutator in the framework of analytic regularization
We calculate the charge-current commutator using analytic regularization and show that it is same as that obtained by dimensional regularization on the dimensionality shell.
119254035
The cluster-core model for the halo structure of light nuclei at the drip lines
Nuclei at both the neutron- and proton-drip lines are studied. In the cluster?core model, the halo structure of all the observed and proposed cases of neutron- or proton-halos is investigated in terms of simple potential energy surfaces calculated as the sum of binding energies, Coulomb repulsion, nuclear proximity attraction and the centrifugal potential for all the possible cluster+core configurations of a nucleus. The clusters of neutrons and protons are taken to be unbound, with additional Coulomb energy added for proton-clusters. The model predictions agree with the available experimental studies but show some differences with the nucleon separation energy hypothesis, particularly for proton-halo nuclei. Of particular interest are the halo structures of 11N and 20Mg. The calculated potential energy surfaces are also useful to identify the new magic numbers and molecular structures in exotic nuclei. In particular, N = 6 is a possible new magic number for very neutron-deficient nuclei, but N = 2, Z = 2 and Z = 8 seem to remain magic even for such nuclei, near the drip line.
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.
14488849
Inflaton decay in de Sitter spacetime
We study the decay of scalar fields, in particular the inflaton, into lighter scalars in a de Sitter spacetime background. After providing a practical definition of the rate, we focus on the case of an inflaton interacting with a massless scalar field either minimally or conformally coupled to the curvature. The evolution equation for the expectation value of the inflaton is obtained to one loop order in perturbation theory and the decay rate is recognized from the solution. We find the remarkable result that this decay rate displays an equilibrium Bose-enhancement factor with an effective temperature given by the Hawking temperature H/2{pi}, where H is the Hubble constant. This contribution is interpreted as the {open_quotes}stimulated emission{close_quotes} of bosons in a thermal bath at the Hawking temperature. In the context of new inflation scenarios, we show that inflaton decay into conformally coupled massless fields slows down the rolling of the expectation value. Decay into Goldstone bosons is also studied. Contact with stochastic inflation is established by deriving the Langevin equation for the coarse-grained expectation value of the inflaton field to one-loop order in this model. We find that the noise is Gaussian and correlated (colored) and its correlations are related tomore » the dissipative ({open_quotes}decay{close_quotes}) kernel via a generalized fluctuation-dissipation relation. {copyright} {ital 1997} {ital The American Physical Society}« less