Results 1 - 10 of 155061
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[en] We discuss our present understanding of the incomplete fusion (ICF) reaction dynamics, the excitation function of six evaporation residues (ERs) have been measured in 16O + 156Gd reaction at projectile energy range, E/A ~ 4.3-6.3 MeV/Nucleon. Some of the ERs are produced directly and indirectly (i.e. through pre-cursor), the pre-cursor contributions have been separated out from the measured cumulative cross-section with the help of Cavinato et al.1. After correcting the pre-cursor contribution, the independent yield has been compared with the statistical model code PACE-22, which describes the fusion reaction cross section. In order to optimize the parameter of the code PACE-2 that reproduces the cross section of all the complete fusion (CF) channels like xn and /or pxn-channels. Using the same set of input parameters, cross section of the ERs populated via incomplete fusion (ICF) channels have been measured. The enhancement in the measured cross section of the ERs populated via ICF channels over the PACE-2 prediction have been measured, which indicates the occurrence of the break-up of projectile 16O into (12C+α) and/or (8Be+2α) leading to ICF reaction dynamics. (author)
[en] The excitation functions of 70Ge(p,n)70As,72Ge(p,n)72As, 74Ge(p,n)74As and 76Ge(p,n)76As reactions were studied from reaction threshold to 30 MeV by using EMPIRE-3.2 and TALYS-1.9 nuclear reaction model codes. This study is important because some isotopes produced are important for positron emission tomography (PET). Direct, pre-compound and compound nuclear reactions are considered as main nuclear reaction mechanisms in the codes. The calculated excitation functions have been compared with available experimental data and found to be in fair agreement. Furthermore, the contributions of various reaction mechanisms have been studied in total reaction cross-section that varies with the incident proton energy. The estimation of induced radio activity in thick Ge target due to the primary interaction is carried out for 1μA, 30 MeV proton beam. (author)
[en] Two different models allowing the calculation of reaction products are confronted with data from α-particle induced reactions. Both models contain a pre-equilibrium part and an equilibrium or compound nucleus part. The models are the exciton model in form of a code written by the author and TALYS. The other model is the intranuclear cascade model in form of the Liege-Saclay formulation incorporated in the PHITS code. The data are angleintegrated proton spectra from reactions with α-particle energies below 720 MeV and excitation functions from multi neutron emission with α-particle energies below 200 MeV.
[en] The azimuthal anisotropy of charged particles produced in =8.16 TeV p+Pb collisions is measured with the ATLAS detector at the LHC. The data correspond to an integrated luminosity of 165 nb that was collected in 2016. Azimuthal anisotropy coefficients, elliptic and triangular , extracted using two-particle correlations with a non-flow template fit procedure, are presented as a function of particle transverse momentum (p) between 0.5 and 50 GeV. The results are also reported as a function of centrality in three different particle p intervals. The results are reported from minimum-bias events and jet-triggered events, where two jet p thresholds are used. The anisotropies for particles with p less than about 2 GeV are consistent with hydrodynamic flow expectations, while the significant non-zero anisotropies for p in the range 9–50 GeV are not explained within current theoretical frameworks. In the p range 2–9 GeV, the anisotropies are larger in minimum-bias than in jet-triggered events. Possible origins of these effects, such as the changing admixture of particles from hard scattering and the underlying event, are discussed.
[en] For 25 LiO–(75 − x) BO–x BiO (where x = 0, 5, 10, 15, 20, 25, 30, 35, and 40 mol%) glasses, gamma-ray and neutrons attenuation features were explored by theoretical approach using ParShield/WinXCOM program, Geant4, and Penelope codes. At Ba (276, 303, 356, and 384 keV), Na (511 and 1280 keV), Cs (662 keV), Mn (835 keV), and Co (1170 and 1330 keV) photon peaks, for all samples, mass attenuation coefficient (μ/ρ), effective atomic number (Z), effective electron density (N), half-value layer (HVL), and mean free path (MFP) parameters have been evaluated using ParShield/WinXCOM program. The μ/ρ values computed by WinXCOM, Geant4, and Penelope codes were compared to check the accuracy, and satisfactory agreement among the values was identified. Moreover, using G–P fitting method as a function of penetration depth (1, 5, 10, 15, 20, 25, 30, 35, and 40 mfp) within the photon energy range of 0.015–15 MeV, exposure buildup factor (EBF) and energy absorption buildup factor (EABF) were derived. For all selected glasses, the effectiveness of the neutrons attenuation has been discussed in terms of macroscopic effective removal cross-section (Σ), coherent scattering cross-section (σ), incoherent scattering cross-section (σ), absorption cross-section (σ), and total neutron cross-section (σ). The 'σ' values have been calculated within 10–10 MeV neutron energy range using the Geant4 code. The μ/ρ possessed larger values at the lowest energy and lower values at higher energy regions for all studied glasses. The μ/ρ, Z, HVL, and MFP values showed enhanced γ-ray shielding capability with BiO content increment in the samples. The 25 LiO–35 BO–40 BiO (mol%) sample by having larger Z and/or Z value, faired lower EBF and EABF values. Largest μ/ρ and Z, and minimal HVL, MFP, EBF, and EABF values of 25 LiO–35 BO–40 BiO (mol%) glass demonstrated its superior γ-ray attenuation ability among all examined glasses. Further, among all glasses, 25 LiO–75 BO (mol%) sample exhibits relatively higher Σ (0.11326 cm) and ‘σ’ (46.109 cm → 0.84607 cm from 1 × 10 MeV → 1×10 MeV neutron energy) values for fast and thermal neutrons attenuation, respectively, indicating its better neutrons absorption competence.
[en] Are chiral theories at present describing experimental NN scattering data satisfactorily? Will the chiral approach offer a framework where fitting and selecting the existing np and pp data can be done without theoretical bias? While predictive power in theoretical nuclear physics has been a major concern in the study of nuclear structure and reactions, the Effective Field Theory (EFT) based on chiral expansions has emerged after Weinberg as a model-independent hierarchy for many-body forces and much progress has been achieved over the last decades. We review some of the issues involved which point to being close to the solution, but also that work remains still to be done to validate the theory. We analyze several examples including zero energy NN scattering and perturbative counter-term-free peripheral scattering where one would expect these methods to work best and unveil relevant systematic discrepancies when a fair comparison to the Granada-2013 NN-database and partial wave analysis based on coarse graining the interaction is undertaken.
[en] Measurements of elastic electron scattering data within the past decade have highlighted two-photon exchange contributions as a necessary ingredient in theoretical calculations to precisely evaluate hydrogen elastic scattering cross sections. This correction can modify the cross section at the few percent level. In contrast, dispersive effects can cause significantly larger changes from the Born approximation. The purpose of this experiment is to extract the carbon-12 elastic cross section around the first diffraction minimum, where the Born term contributions to the cross section are small to maximize the sensitivity to dispersive effects. The analysis uses the LEDEX data from the high resolution Jefferson Lab Hall A spectrometers to extract the cross sections near the first diffraction minimum of C at beam energies of 362 MeV and 685 MeV. The results are in very good agreement with previous world data, although with less precision. The average deviation from a static nuclear charge distribution expected from linear and quadratic fits indicate a 30.6% contribution of dispersive effects to the cross section at 1 GeV. The magnitude of the dispersive effects near the first diffraction minimum of C has been confirmed to be large with a strong energy dependence and could account for a large fraction of the magnitude for the observed quenching of the longitudinal nuclear response. These effects could also be important for nuclei radii extracted from parity-violating asymmetries measured near a diffraction minimum.
[en] The α decay half-lives and the fine structure phenomenon are investigated with fission-like models. A superasymmetric fission path in a configuration space spanned by five degrees of freedom is determined in accordance with the least action principle. The deformation energy is evaluated within the macroscopic–microscopic approach while the inertia is obtained in the framework of the cranking model. The single particle levels schemes are calculated connecting the ground state of the parent nucleus and the asymptotic configuration of two separated nuclei. The probabilities to find different seniority configurations are obtained by solving time-dependent pairing equations generalized by including the Landau-Zener effect and the Coriolis coupling. The microscopic equations of motion for even numbers of particles are deduced, those for odd-nuclear systems being obtained in previous works. The models used in the calculations are reviewed within a detailed description. The microscopic equations of motion are solved by starting from the ground state configuration and arriving at the scission point. A description of all the possible configurations at scission together with their realization probabilities is given. By fitting the inter-nuclear velocity, the best agreement between experimental and theoretical hindrance factors is retained. The theoretical results for the α decay half-lives for Po and Bi are compared with experimental data showing discrepancies ranging over three orders of magnitude. The accuracy of the model concerning the calculations of the half-lives for different channels is discussed. The connections between the classical theories concerning the preformation of the α particle and the fission-like descriptions are highlighted.
[en] The zero-energy astrophysical S-factor for the fusion process p + p → d + e + ν is calculated using pionless effective field theory (/πEFT). In the present study, the order-by-order results are reproduced according to a new suggested power counting. The short range interactions in the S-wave pp scattering at leading order and the corrections in the next-to-leading order including the Coulomb interaction are introduced. In addition the Coulomb interaction between the incoming protons has been considered. The new nuclear /πEFT amplitude is compatible with renormalization-group invariance.
[en] The nuclear ground-state properties and the nuclear deformation of some even-even Silicon isotopes have been investigated. The spherical Skyrme - Hartree - Fock method that includes Hartree - Fock calculations in addition to several common Skyrme parameterizations, such as SkB, SkM*, SkE, SkX, SLy4, Skxta, SkP, UNEDF0, and UNEDF1, has been used to calculate the nuclear ground-state charge density distributions and the associated charge radii for 28Si and 30Si, because of the availability of the experimental data for these two stable isotopes. Furthermore, the mass, neutron and proton densities with the associated radii, the binding energies, the neutron skin thickness, and the charge form factors have been calculated for 24-42Si isotopes using SkM* parameterization. The quadrupole deformations of the selected isotopes have been investigated in terms of the potential energy curves that were deduced as a function of the quadrupole deformation parameters using the axially deformed configurational Hartree - Fock - Bogolyubov calculations with SkM* parameterization. (author)