Search

We study the di-neutron correlations in the super neutron-rich nucleus 7H with the AMD triple-S (AMD superposition of selected snapshots). 7H is the most neutron-rich nucleus in the neutron ratio to the proton (N/Z = 6). And the strong di-neutron correlations are expected due to the weak binding properties. In this paper, the mixing of di-neutron cluster components is estimated by calculating the squared overlap with the di-neutron condensate type wave function. The calculated results show significant mixing of di-neutron (t + 2n + 2n) components (70 ~ 80%). [ABSTRACT FROM AUTHOR]

Understanding the structure of very neutron-rich nuclei is critical to developing reliable and robust models of the nucleus. For nuclei near the neutron drip-line, where the neutron removal energy approaches zero, several features of nuclear structure are much more important than they are in stable nuclei. The neutron pairing energy becomes comparable to the neutron removal energy and nuclei with odd neutron numbers tend to be unbound while their even neighbors remain bound. Additionally, shell effects can be greatly altered by the absence of protons in the same valence orbitals occupied by the neutrons. The lack of the stabilizing influence of protons in similar orbits allows for the tensor interaction between these weakly bound neutrons and the core nucleons to alter the energies of single particle levels. These changes lead to the disappearance of well-known magic numbers and the appearance of new sub-shell closures that have the requisite properties of a magic number: enhanced stability, a large excitation energy for the first excited state, and spherical shape. [ABSTRACT FROM AUTHOR]

As was found in our previous study, the presence of the thermal peak in neutron spectra measured by the 3He ionization chamber makes it difficult to use its complete response function in an unfolding process. In order to significantly reduce the thermal peak counting rate, an active method of rejecting low energy neutrons (<180 eV) based on their time-of-flight has been developed and tested. The method required a modification of the proton accelerator beam line to produce short pulses of protons. The ratio of the number of detection events above thermal peak to the number of events scored in the thermal peak has been improved by a factor of 5. [ABSTRACT FROM AUTHOR]

To extract the nuclear structure function of light nuclei like 3He and 3H, the convolution of proton and neutron structure functions in the conventional approach could not explain the modification of nuclear structure functions of these nuclei because of some nuclear medium effects. There are some models that have some success to explain the modification of nuclear structure functions in limited x range. So in this investigation the quark exchange model is considered to extract the nuclear medium effect of this phenomenon (quark exchange effect) for nuclear structure functions of 3He and 3H nuclei. The Fermi motion part of the nuclear structure functions for these nuclei is extracted by taking the GRV’s neutron and proton structure functions in the conventional approach. So the nuclear structure functions and the EMC ratios of 3He and 3H nuclei are calculated by considering both Fermi motion and the nuclear medium effect of quark exchange. Finally the extracted results are compared with available data. [ABSTRACT FROM AUTHOR]

A model for estimating proton SEU cross sections from heavy-ion test data has been extended to include 14 MeV neutrons. Accuracy is less consistent for neutrons, but predictions can still be used for upper bounds. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Physics is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Neutrons and light charged particles produced in 62.9MeV proton-induced reactions on208Pb were measured during a single experiment performed at the CYCLONE facility in Louvain-la-Neuve (Belgium). Two independent experimental set-ups were used to extract double differential cross-sections for neutrons, protons, deuterons, tritons,3He and alpha-particles. Charged particles were detected using a set of Si- Si- CsI telescopes from 25° to 155°, by step of 10 degrees. Neutrons were measured using shielded DeMoN counters, liquid NE213 scintillators, at 24°, 35°, 55°, 80° and 120°. These data allowed the determination of angle differential, energy differential and total production cross-sections. A comparison with theoretical calculations (MCNPX, FLUKA and TALYS) has been performed. It shows that the neutron and proton production rates are well predicted by MCNPX, using the INCL4 option. All the other codes underestimate the neutron production whereas they overestimate the proton one. For composite particles, which represent 17% of the charged particle total reaction cross-section, neither the shape nor the amplitude of the cross-sections are correctly predicted by the models. [ABSTRACT FROM AUTHOR]

A numerical analysis of the polarization vector of τ's produced through quasielastic ντ and $\bar{\nu}_\tau$ interactions with nucleons is given with two models for vector electromagnetic form factors of proton and neutron. The impact of G parity violating axial and vector second-class currents is investigated by applying a simple heuristic model for the induced scalar and tensor form factors. [ABSTRACT FROM AUTHOR]

Results of WNR continuous spectrum irradiations are compared to mono-energetic proton and neutron data according to the JEDEC-JESD89 test procedure. A good correlation between these two methods is found particularly when 500 MeV proton cross-section is used instead of the one at 150 MeV. The increased contribution of the low energy part of the spectrum for modern devices is also discussed. Finally, the influence of front side and back side irradiations is studied at different energies and for several devices from 0.8 μm to 0.18 μm technologies. [ABSTRACT FROM AUTHOR]

Charge form factors corresponding to proton density distributions in exotic nuclei, such as 6,8He, 11Li, 17,19B and 14Be are calculated and compared. The results can be used as tests of various theoretical models for the exotic nuclei structure in possible future experiments using a colliding electron-exotic nucleus storage ring. The result of such a comparison would show the effect of the neutron halo or skin on the proton distributions in exotic nuclei. [ABSTRACT FROM AUTHOR]

Single-particle separation energies of protons or neutrons in nuclei near the closed shells are examined in the chains of isotopes or isotones. From the observed dependences we determine spins and parities of the single-particle orbitals and their sequence in nuclei far from the stability line, where direct experimental information on single-particle characteristics is not available at present. [ABSTRACT FROM AUTHOR]

We have performed shell model calculations for 134Te, 130,134Sn, and 132,134Sb using a realistic effective interaction derived from the CD-Bonn nucleon-nucleon potential. The calculated results are compared with the available experimental data. The main aim of this study was to put to a comprehensive test our realistic effective interaction in the A = 132 region. A very good agreement is obtained for all the five nuclei considered. [ABSTRACT FROM AUTHOR]

Differential cross-sections for quasi-free π0 photoproduction from the proton and neutron bound in the deuteron have been measured for Eγ 200-400 MeV at θγlab = 136.2° using the Glasgow photon tagger at MAMI, the Mainz 48 cm ø × 64 cm NaI(Tl) photon detector and the Göttingen SENECA recoil detector. For the proton measurements made with both liquid-deuterium and liquid-hydrogen targets allow direct comparison of "free" π0 photoproduction cross-sections as extracted from the bound-proton data with experimental free cross-sections which are found to be in reasonable agreement below 320 MeV. At higher energies the "free" cross-sections extracted from quasi-free data are significantly smaller than the experimental free cross-sections and theoretical predictions based on multipole analysis. For the first time, "free" neutron cross-section have been extracted in the Δ-region. They are also in agreement with the predictions from multipole analysis up to 320 MeV and significantly smaller at higher photon energies. [ABSTRACT FROM AUTHOR]

It is imperative that lattice QCD serve to develop our understanding of hadron structure and, where possible, to guide the interpretation of experimental data. There is now a great deal of effort directed at the calculation of the electroweak form factors of the nucleon, where for example, measurements at Jefferson Laboratory have recently revealed surprising behaviour in the ratio GE/GM. While, for the present, calculations within the framework of lattice QCD are limited to relatively large quark mass, there has been considerable progress in our understanding of how to extrapolate to the chiral limit. Here we report the results of the application of these techniques to the most recent form factor data from the QCDSF Collaboration. The level of agreement with all of the form factors, for Q² below 1 GeV², is already impressive. [ABSTRACT FROM AUTHOR]

The influences of the neutron-to-proton ratio N/Z of fissioning systems on particle emission for isotopic sources of 189,202,212Po and for isobaric sources of 202Tl, 202Po and 202Fr are investigated within the framework of Smoluchowski equation. It is shown that the multiplicity of emitted particles shows a strong dependence on the N/Z ratio of the fissioning sources. Calculations also show that when the N/Z ratio of a fissioning system becomes large, charged-particle emission becomes no longer sensitive to viscosity strength, which means that for those systems with larger N/Z ratio, protons and γ-particles are not good probes of extracting the value of the viscosity coefficient in fission. [ABSTRACT FROM AUTHOR]

β-decay half-lives around 78Ni and 132Sn are studied with proton-neutron Quasiparticle Random Phase Approximation on the basis of Skyrme-Hartree-Fock (SHF) method. We take into account tensor force correlation in calculating the ground and excited states and find it improves the half-life of 132Sn. However, the Q value is still underestimated. We also discuss that half-lives do not strongly depend on type of particle-particle interaction in isospin T = 0 channel. [ABSTRACT FROM AUTHOR]

We present the results of fully self-consistent RPA calculation for low-frequency negative-parity modes built on superdeformed states in the 40Ca region. The RPA calculation was carried out using the mixed representation on the three-dimensional Cartesian mesh in a box. The SD shell structure provides a very favorable situation for octupole shape fluctuations, and we show that the coherent excitation of protons and neutrons play an important role in the emergence of strongly collective octupole vibrations buit on the SD states in the N = Z nuclei, 32S, 36Ar, 40Ca and 44Ti. In particular, the calculation suggests that a low-frequency, strongly collective Kπ = 1- octupole vibration appears on the SD state in 40Ca. [ABSTRACT FROM AUTHOR]