Nucleons In Nucleus Research Articles

STUDY OF OCTUPOLE DEFORMATION OF NUCLEI IN CHAIN OF ISOTONS IN THE REGION OF ACTINIDES IN THE MEAN FIELD APPROXIMATION

Calculations of the properties of even-even isotones N = 134 of nuclei with Z = 86–96 were carried out in the Hartree-Fock-Bogolyubov approximation, taking into account the axial symmetry of nuclei with forces Skyrme (SkM*, SLy4). Pairing of nucleons in nuclei is described by zero-range pairing forces of mixed type with different sets of pairing force constants. In the calculations we used constrained conditions on the parameters of the quadrupole and octupole deformations of the nuclei. It is shown that for the considered chain of isotones the octupole deformation of nuclei strongly depends on the choice of parameters of the nucleon pairing force and weakly depends on the type of parameterization of the Skyrme forces used in this study.

Reconstruction of Bremsstrahlung γ-rays spectrum in heavy ion reactions with Richardson-Lucy algorithm

The high momentum tail (HMT) in the momentum distribution of nucleons above the Fermi surface has been regarded as an evidence of short-range correlations (SRCs) in atomic nuclei. It has been showcased recently that the np Bremsstrahlung radiation in heavy ion reactions can be used to extract HMT information. The Richardson-Lucy (RL) algorithm is introduced to the reconstruction of the original Bremsstrahlung γ-ray energy spectrum from experimental measurements. By solving the inverse problem of the detector response to the γ-rays, the original energy spectrum of the Bremsstrahlung γ in 25 MeV/u 86Kr + 124Sn has been reconstructed and compared to the isospin- and momentum-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) simulations. The analysis based on hypothesis test suggests the existence of the HMT of nucleons in nuclei, in accordance with the previous conclusions. With its effectiveness being demonstrated, it is feasible to apply the RL algorithm in future experiments of measuring the Bremsstrahlung γ-rays in heavy ion reactions.

The Optical Model Absorption Term in the Frame of Fractional Derivatives

The complex optical model has been widely used to describe the elastic scattering of the nucleon–nucleus. The imaginary term of the optical potential takes into account the non-elastic scattering processes. This term was taken to be a Woods–Saxon form factor or its derivative to simulate the volume absorption or the absorption localized at the surface of the target, respectively. In this study, a fractional derivative of the Woods–Saxon potential with 0<α<1 was used, where α=0 and α=1 give the volume and the surface absorption form factor, respectively.

Density and energy dependent semi-microscopic optical potential of nucleon–nucleus elastic scattering

A nonlocal velocity-dependent optical potential was used to study the angular distribution of the differential cross section of nucleon–nucleus elastic scattering. The potential parameters were calculated by fitting elastic angular distributions over a wide range of energy (10-65 MeV) and mass (12-208). The real part of the local optical potential was calculated using the CDM3Y6-Paris interaction, whereas the imaginary part was a Woods-Saxon form factor and its derivative.

Exploring Short-Range Correlations in symmetric nuclei: Insights into contacts and entanglement entropy

The Short-Range Correlations between nucleons in nuclei are regarded as a complex system. We investigate the relationship between the orbital entanglement entropy of SRCs Sij in nuclear structures and Tan contact cij, and find that the orbital entanglement entropies and Tan contacts corresponding to proton-proton SRC pairs and neutron-proton SRC pairs in nuclei demonstrate a scaling relation. More specifically, the proportionality of entanglement entropy between proton-proton pairs and neutron-proton pairs is directly related to the ratio of nuclear contacts within the atomic nucleus, demonstrating an approximate ratio of 2.0. Our research suggests that this scaling relationship should hold true for all symmetric nuclei, furthermore, we offer a possible explanation for this phenomenon.

Verification of T Invariance in the Total Interaction Cross Section of Neutrons with Unpolarized Nuclei Using the Polarization–Asymmetry Theorem

To date, the violation of T invariance (TI) has been experimentally established for the decays [J.H.Christenson et al., Phys. Rev. Lett.13, 138 (1964)] and oscillations [A. Angelopoulos et al., Phys. Lett. B444, 43 (1998)] of neutral kaons. Phenomenologically, TI violation in the system of neutral kaons is associated with the difference of the Kobayashi–Maskawa phase from zero (or from π) in the standard model of the electroweak interaction. For nucleon–nucleus interactions, this phase turns out to be very small [P.Herszeg, inSymmetries and Fundamental Interactions in Nuclei, World Scientific, Singapore (1995), p.89)]. Estimates of the nucleon–nucleon matrix element corresponding to TI violation in various models are given in [V. Gudkov, inFundamental Physics with Pulsed Neutron Beams, World Scientific, Singapore (2001), p. 117]. All these estimates are small and have a large spread. Therefore, the verification of TI in nuclear processes actually means a search for other mechanisms for its violation. Below is a description of the experimental methods for TI verification in the total interaction cross sections of low-energy resonance neutrons with unpolarized nuclei with the use of the polarization–asymmetry (PA) theorem.

New bound-state energy of double magic number plus one nucleon nuclei with a relativistic and non-relativistic mean-field approach in 3D-RNCQS and 3D-NRNCQS symmetries

New bound-state energy of double magic number plus one nucleon nuclei with a relativistic and non-relativistic mean-field approach in 3D-RNCQS and 3D-NRNCQS symmetries

INVESTIGATION OF THE INFLUENCE OF THE NUCLEON PAIRING FORCE ON THE OCTUPOLE DEFORMATION OF URANIUM AND THORIUM ISOTOPES IN THE MEAN-FIELD APPROXIMATION

In the Hartree-Fock-Bogolyubov approximation and the axial symmetry of nuclei with Skyrm forces SkM*, the properties of U with A = 220 – 232 and Th with A = 218 – 230 isotopes were calculated. In addition, the properties of U and Th near the neutron drip line A = 280 – 292 were calculated. Pairing of nucleons in nuclei is described by pairing forces of zero radius of action of a mixed type with different sets of pairing force constants. In our calculations, we used constrained conditions on the parameters of quadrupole β2 and octupole β3 deformations of nuclei. It is shown that for the considered U isotopes, as well as Th isotopes, the deformation of the β3 nuclei strongly depends on the choice of the parameters of the nucleon pairing force.

Phase shift and cross section analysis of nucleon–nucleon and nucleon–nucleus scattering using second Pöschl–Teller potential

In view of nuclear structure calculations, the second Pöschl–Teller potential is parameterized to study nucleon–nucleon and nucleon–nucleus elastic scattering. By exploiting the variable phase approach to potential scattering, phase parameters, cross sections, analyzing powers, etc., are computed and compared with earlier works. The calculated cross sections agree with the experiments below 25 MeV within the error bars for the (n-p) and (n-d) systems.

DDFRG2: Double-Differential FRaGmentation model for pion production in high energy nuclear collisions

A set of Double-Differential FRaGmentation (DDFRG) models for production of fragments from nucleon–nucleus and nucleus–nucleus collisions, relevant to space radiation, is currently being developed. DDFRG1 was a previous model developed for production of protons and light ions. A new model for pion production is developed in the present work and is called DDFRG2, which is based upon thermal production of pions from a central fireball source. The Lorentz-invariant double-differential cross section is calculated in the central fireball frame, and is Lorentz transformed to the laboratory frame, which results in a closed-form analytic formula involving no numerical integration, and which can be run very efficiently in radiation transport codes. The Lorentz-invariant double-differential cross section is then integrated over angle to give the single-differential energy spectral distribution. The calculated Lorentz-invariant double-differential cross sections are compared to an extensive data set containing over 1000 data points. Agreement between model calculations and data is found to be excellent.

Study of6,8He+p elastic scattering using the BHF formalism with three-body forces

In the present work, we have analyzed the elastic scattering data of6He+p at 25.6, 38.6, 40.9, and 71 MeV/A and8He+p at 15.6, 25.6, 32.5, 66, and 72 MeV/A, using the microscopic local optical potential calculated within the framework of the Brueckner–Hartree–Fock (BHF) formalism. The calculation requires mainly two inputs: (1) the nucleon–nucleon (NN) interaction and (2) the nucleon distributions in target nuclei. In the present work, realistic internucleon (NN) potential from Argonne v18 (AV18) and the Urbana IX (UVIX) model of three-body forces with several nucleon density distributions are used for generating the nucleon–nucleus optical potential. We have used the exact method for calculating both the direct and the exchange parts of the spin–orbit potential. We confirm the earlier results that the spin–orbit potential for these neutron-rich nuclei is diffused and extended. Our results show that the different density distributions reproduce rather well the experimental differential cross sections for both isotopes, while the phenomenological density with a two-neutron halo gives satisfactory results for6He-p analyzing power data. None of the densities used for8He can reproduce the experimentally analyzed power data. Our analysis reveals that the calculated microscopic optical potentials, with and without three-body forces using the BHF approach, provide satisfactory agreement with the elastic scattering data for6,8He+p.

QCSH: A full quantum computer nuclear shell-model package

The nuclear system is a promising area for demonstrating practical quantum advantage. A comprehensive computation of a nuclear system in a classical computer is beyond the capacity of current classical computers. With the rapid development of hardware, the prospect of using quantum computers in nuclear physics is close at hand. In this paper, we report a full quantum package, QCSH, for solving a nuclear shell model in a quantum computer. QCSH uses the linear combination of the unitary formalism of quantum computing and performs all calculations in a quantum computer. The complexities of qubit resource and the number of basic gates of QCSH are both polynomials to the number of nucleons in nuclei. For example, QCSH is used to calculate the binding energies of 12 light nuclei (i.e., 2H, 3H, 3He, 4He, 6Li, 7Li, 12C, 14N, 16O, 17O, 23Na, and 40Ca). Moreover, we experimentally demonstrate the calculation of deuteron binding energy using a superconducting quantum processor. The result indicates that QCSH can provide meaningful results already in near-term quantum devices.

Mass-area equivalence in classical physics and aspects of mutual shielding of objects

The physical and mathematical aspects of the mutual spatial shielding of interacting elements in the framework of classical physics are considered. The mass-area equivalence is introduced for the formal unification of the Newtonian theory of gravity with the kinetic theories of Descartes-Fatio-Le Sage. A mathematical equation describing the dependence of the mutual shielding of objects on their size, number and relative location is proposed. Spatial mutual shielding is considered for mass-forming elements—nucleons in the atomic nucleus and atomic nuclei in ordinary substances. The close shielding is distinguished when the distance between the shielding elements is commensurate with their size, which is typical for nucleons in atomic nuclei and the far shielding, when the distance between the elements is much larger than their size, which is typical for atomic nuclei in ordinary substances. An analytical expression for the binding energy of nucleons in atomic nucleus is obtained. It allows us to estimate the distance between nucleons in the nucleus and consider stability of nuclei as a function of the distance between nucleons, which increases due to an increase in the Coulomb repulsion force with an increase in the number of protons. One of the three ideas of Dirac, presented by him for the further development of the physical theory, is implemented: taking into account the sizes of elementary particles—nucleons.

Influence of nucleon structure on spin correlation coefficients in elastic lepton-deuteron scattering

Spin correlation coefficients in elastic scattering of leptons on the deuteron are studied in the one-photon-exchange Born approximation within the limit of zero lepton mass. Numerical estimations for the spin correlation coefficients caused by a polarized beam and a vector polarized target are presented and analyzed at various beam energies and scattering angles in two coordinate systems which are relevant for experiment. The influence of the obtained results on the nucleon structure is investigated, and a considerable dependence at incident beam energies greater than 1[Formula: see text]fm[Formula: see text] and backward scattering angles is found. The estimated results are of particular interest for encouragement of experimental measurements of lepton-deuteron scattering which aim for accurate calculation of the charge radius of the proton to a high degree of precision. These results may also stimulate new generation of measurements of different physical observables very sensitive to the spin structure of the nucleon and light nuclei.

Spin correlation coefficients in lepton–deuteron elastic scattering and their sensitivity to realistic NN potentials

Spin correlation coefficients in the elastic scattering of leptons on the deuteron, [Formula: see text], are studied in the one-photon-exchange approximation within the limit of zero lepton mass. Numerical estimations for the spin correlation coefficients caused by a polarized beam and a vector polarized target are given. The estimated spin correlation coefficients are analyzed at various values of beam energy and scattering angle. The sensitivity of the obtained results to the choice of realistic NN potential used for the deuteron wave function is investigated. We found a considerable dependence of the results on the realistic deuteron wave functions at incident beam energies greater than 0.4 GeV and backward scattering angles. The estimated results are of particular interest for encouragement of experimental measurements of lepton–deuteron scattering which aim for accurate calculation of the charge radius of the proton to a high degree of precision. These results may also stimulate new generation of measurements of different physical observables very sensitive to the spin structure of the nucleon and light nuclei.

Abnormal Bound Systems

It is taken for granted that bound systems are made of massive constituents that interact through particle exchanges (charged particles interacting via photon exchanges, quarks in elementary particles interacting via gluon exchanges, and nucleons in nuclei interacting via meson exchanges). However, as was recently theoretically found, there exist systems dominated by exchange particles (at least for the zero exchange masses). In these systems, the contribution of massive constituents is negligible. These systems have a relativistic nature (since they are mainly made of massless particles moving at the speed of light), and therefore, they cannot be described by the Schrödinger equation. Though these results were found so far in the simple Wick–Cutkosky model (spinless constituents interacting via the ladder of spinless massless exchanges), the physical ground for their existence seems to be rather general.

Nucleon momentum gap in asymmetric nuclear matter

For more than half a century, nucleons were considered to move continuously in the nuclei. Recent electron-scattering experiments indicate about 20--25% of nucleons in heavier nuclei are involved in the neutron-proton short-range correlations. Nucleons in the nuclei thus have abnormal behavior unlike those in the noninteraction fermi gas. In the neutron-rich nuclei, around the Fermi momentum, the neutron-proton short-range correlations lead to a momentum gap in the proton momentum distribution, which is circumstantially supported by the pionic experimental data. Likewise, there should also be a neutron momentum gap in the proton-rich nuclei. Nucleon momentum gap is thought to have profound and extensive implications in the studies ranging from particle physics to neutron stars as well as ultracold atomic gases.

Nucleon–nucleus inelastic scattering by Manning–Rosen distorted nonlocal potential

Within the framework of non-relativistic quantum scattering theory, we treat the charged hadron scattering by replacing the nuclear interaction by a separable nonlocal one and the electromagnetic part by the Manning–Rosen potential. The off-energy-shell scattering is rigorously studied by this additive interaction by including the effect of electromagnetic interaction. The exact analytical expressions for the off-shell solutions and half-shell T-matrix are obtained in maximal reduced form. The half-shell T-matrix for the proton–oxygen system is computed and the resultant phase shifts are found in order.

Imprints of high-momentum nucleons in nuclei on hard photons from heavy-ion collisions near the Fermi energy

The short-range correlation (SRC) induced by the tensor force in the isosinglet neutron-proton interaction channel leads to a high-momentum tail (HMT) in the single-nucleon momentum distributions n(k) in nuclei. Owing to the remaining uncertainties about the tensor force, the shape of the nucleon HMT may be significantly different from the dilute interacting Fermi gas model prediction $n(k) \sim1/k^4$ similar to the HMT in cold atoms near the unitary limit. Within an isospin- and momentum-dependent Boltzmann-Uehling-Uhlenbeck transport model incorporating approximately the nucleon HMT, we investigate hard photon emissions in $^{14}$N+$^{12}$C and $^{48}$Ca+$^{124}$Sn reactions at beam energies around the Fermi energy. Imprints of different shapes of the HMT on the energy spectrum, angular distribution and transverse momentum spectrum of hard photons are studied. While the angular distribution does not carry any information about the shape of the nucleon HMT, the energy spectra and especially the mid-rapidity transverse momentum spectra of hard photons are found to bare strong imprints of the shapes of nucleon HMTs in the two colliding nuclei.

Nuclear Dynamics and Reactions in the Ab Initio Symmetry-Adapted Framework

We review the ab initio symmetry-adapted (SA) framework for determining the structure of stable and unstable nuclei, along with related electroweak, decay, and reaction processes. This framework utilizes the dominant symmetry of nuclear dynamics, the shape-related symplectic [Formula: see text] symmetry, which has been shown to emerge from first principles and to expose dominant degrees of freedom that are collective in nature, even in the lightest species or seemingly spherical states. This feature is illustrated for a broad scope of nuclei ranging from helium to titanium isotopes, enabled by recent developments of the ab initio SA no-core shell model expanded to the continuum through the use of the SA basis and that of the resonating group method. The review focuses on energies, electromagnetic transitions, quadrupole and magnetic moments, radii, form factors, and response function moments for ground-state rotational bands and giant resonances. The method also determines the structure of reaction fragments that is used to calculate decay widths and α-capture reactions for simulated X-ray burst abundance patterns, as well as nucleon–nucleus interactions for cross sections and other reaction observables.