Search results

Filter

Filetype

Your search for "*" yielded 530841 hits

Medium polarization effects on the superuidity of finite nuclei and of the inner crust of neutron stars

We review recent progress made in understanding the role of medium polarization on superuidity in finite nuclei and in the inner crust of neutron stars. The interweaving of collective and quasiparticle degrees of freedom is treated within the framework of Nuclear Field Theory, propagating the basic renormalization processes through the Nambu-Gor’kov equations. It is then possible to obtain quantit

Coherence and the Successive Contribution in Two-Neutron Transfer reactions

In this short letter we briefly address two important points of two-neutron transfer reactions, namely the successive nature of the process and the role of pairing correlations during this sequential transfer. The discussion is made within the 2-step DWBA formalism. The calculations were carried out making use of software specifically developed for this purpose, which includes successive, simultan

Quantitative study of coherent pairing modes with two-neutron transfer : Sn isotopes

Pairing rotations and pairing vibrations are collective modes associated with a field, the pair field, which changes the number of particles by two. Consequently, they can be studied at profit with the help of two-particle transfer reactions in superfluid and in normal nuclei, respectively. The advent of exotic beams has opened, for the first time, the possibility to carry out such studies in medi

Calculation of the transition from pairing vibrational to pairing rotational regimes between magic nuclei Sn100 and Sn132 via two-nucleon transfer reactions

Absolute values of two-particle transfer cross sections along the Sn-isotopic chain are calculated. They agree with measurements within errors and without free parameters. Within this scenario, the predictions concerning the absolute value of the two-particle transfer cross sections associated with the excitation of the pairing vibrational spectrum expected around the recently discovered closed sh

Investigation of the self activity and high energy γ-rays response of a 1" × 1" and 3" × 3" LaBr3:Ce scintillators

The properties of a cylindrical 1" × 1" and 3" × 3" LaBr3:Ce scintillators (Brillance 380) have been investigated. The first crystal has been analyzed in terms of its self activity due to unstable contaminants emitting a and β particles eventually followed by γ-rays. Coincidence measurements between LaBr3:Ce signals and γ-rays in a HPGe detector were made. The second crystal has been irradiated wi

Quasiparticle renormalization and pairing correlations in spherical superfluid nuclei

Within the framework of nuclear field theory (NFT), the spectrum of atomic nuclei is described in terms of collective and quasiparticle degrees of freedom, that is, of elementary modes of excitation that are directly related to experiment and of their coupling, whose strength and form factors are the basic ingredients entering in the calculations of absolute cross sections of inelastic and of one-

Dyson treatment of NFT medium polarization processes in superfluid nuclei

We discuss the solution of the Dyson equation (also known as the Nambu-Gor'kov equation) for the case of medium polarization Nuclear Field Theory (NFT) processes in nuclei, and apply it to the nucleus 120Sn. Starting from a mean field obtained with the Sly4 effective nucleon-nucleon force, (mk = 0.7), we renormalize the single-particle states and the pairing interaction through the coupling to col

Reaction mechanism of two-neutron transfer in DWBA

We present a brief introduction to the second order DWBA reaction formalism which we have used to perform the theoretical analysis of two-nucleon transfer reactions induced both by heavy and light ions. We also show an example of such a calculation, emphasizing the connection between the structure aspects of the problem and the resulting predicted two-neutron transfer cross section. The calculatio

Nuclear surface dynamics and pairing correlations

We solve the Nambu-Gor'kov equations in 120Sn, demonstrating that the coupling of quasiparticles with collective surface vibrations renormalizes the low-lying part of the nuclear spectrum and influences pairing correlations in a substantial way.

Two-particle transfer cross sections and nuclear superfluidity

The six measured ASn(p,t)A-2Sn(gs) transfer absolute differential cross sections (A = 112, 116, 118, 120, 122, and 124) are calculated within the framework of DWBA taking into account successive, simultaneous and non-orthogonality contributions, and making use of BCS spectroscopic amplitudes which reproduce the overall distortion of the Fermi distribution around εF . Theory provides an overall acc

Dynamical processes in the structure of halo nuclei and their experimental evidence

High polarizability and halo phenomena are strongly correlated, as evidenced by the qualitative changes of the nuclear spectrum which arise taking into account the dynamical coupling of the valence neutrons with the collective vibrations of the system. Direct experimental evidence of their role in the induced pairing interaction binding the halo neutrons of 11Li to the core 9Li is provided by the

Cooper pair transfer in nuclei

The second-order distorted wave Born approximation implementation of two-particle transfer direct reactions which includes simultaneous and successive transfer, properly corrected by non-orthogonality effects, is tested with the help of controlled nuclear structure and reaction inputs against data spanning the whole mass table, and showed to constitute a quantitative probe of nuclear pairing corre

Contribution of Nuclear Field Theory medium effects to the pairing gap

We calculate the different contributions to the pairing gap for the case of the superfluid nucleus 120Sn, making use of the Dyson equation (also known as the Nambu-Gor'kov equation in the case of superfluid systems) to propagate leading medium polarization Nuclear Field Theory (NFT) processes to all orders. Starting from a mean field obtained with the SLy4 effective force (mk ≈ 0.7), we renormaliz

A parametric study on cavitation flow through steam trap valves under high pressure difference

Steam trap valves are mainly used in thermal power systems to pour out condensate water and keep steam inside. While flowingthrough steam trap valves, the condensate water is easy to reach cavitation, which may cause serious damage to the pipingsystem. In this paper, in order to suppress cavitation inside steam trap valves, effects of valve body geometrical parametersincluding orifice diameter, in

Effect of droplet superficial velocity on mixing efficiency in liquid-liquid droplet flow

Enhancement of mixing efficiency in droplets is of great importance to extend the industrial applications of the liquid-liquid twophase flow in micro-scale. In this paper, mixing efficiency in droplets is investigated via the VOF (volume of fluid) method coupledwith UDS (user defined scalar) model. The cross-shaped T junction with a square cross-section is designed and used for dropletformation. D