Nucleon Configurations Research Articles

Photoproduction of pion-nucleon pairs on atomic nuclei and isobar configurations

The photoproduction of pion-nucleon pairs on atomic nuclei in the Δ(1232) resonance region was analyzed. The contributions of both nucleon and isobar configurations in the ground state of nuclei were taken into account. The cross section of pion-proton pair photoproduction in the 16O(γ,π0p) reaction was calculated.

Kaon condensation and multi-strange matter

We report on dynamical calculations of multi- K ¯ hypernuclei, which were performed by adding K ¯ mesons to particle-stable configurations of nucleons, Λ and Ξ hyperons. The K ¯ separation energy as well as the baryonic densities saturate with the number of antikaons. We demonstrate that the saturation is a robust feature of multi- K ¯ hypernuclei. Because the K ¯ separation energy B K ¯ does not exceed 200 MeV, we conclude that kaon condensation is unlikely to occur in finite strong-interaction self-bound { N , Λ , Ξ } strange hadronic systems.

Multi-K¯hypernuclei

Relativistic mean-field calculations of multi-K hypernuclei are performed by adding K{sup -} mesons to particle-stable configurations of nucleons, {lambda} and {xi} hyperons. For a given hypernuclear core, the calculated K separation energy B{sub K} saturates with the number of K mesons for more than roughly 10 mesons, with B{sub K} bounded from above by 200 MeV. The associated baryonic densities saturate at values 2-3 times nuclear-matter density within a small region where the K-meson densities peak, similarly to what was found for multi-K nuclei. The calculations demonstrate that particle-stable multistrange (N,{lambda},{xi}) configurations are stable against strong-interaction conversions {lambda}{yields}NK and {xi}{yields}NKK, confirming and strengthening the conclusion that kaon condensation is unlikely to occur in strong-interaction self-bound strange hadronic matter.

A Monte Carlo generator of nucleon configurations in complex nuclei including nucleon–nucleon correlations

We developed a Monte Carlo event generator for production of nucleon configurations in complex nuclei consistently including effects of nucleon–nucleon (NN) correlations. Our approach is based on the Metropolis search for configurations satisfying essential constraints imposed by short- and long-range NN correlations, guided by the findings of realistic calculations of one- and two-body densities for medium-heavy nuclei. The produced event generator can be used for Monte Carlo (MC) studies of pA and AA collisions. We perform several tests of consistency of the code and comparison with previous models, in the case of high energy proton–nucleus scattering on an event-by-event basis, using nucleus configurations produced by our code and Glauber multiple scattering theory both for the uncorrelated and the correlated configurations; fluctuations of the average number of collisions are shown to be affected considerably by the introduction of NN correlations in the target nucleus. We also use the generator to estimate maximal possible gluon nuclear shadowing in a simple geometric model.

Solution of the Skyrme–Hartree–Fock–Bogolyubov equations in the Cartesian deformed harmonic-oscillator basis.: (VI) hfodd (v2.40h): A new version of the program

Solution of the Skyrme–Hartree–Fock–Bogolyubov equations in the Cartesian deformed harmonic-oscillator basis.: (VI) hfodd (v2.40h): A new version of the program

Extended investigation of superdeformed bands inTb151,152nuclei

A detailed study of known and new SD bands in Tb isotopes has been performed with the use of the EUROBALL IV gamma-ray array. The high-statistics data set has allowed for the extension of known SD bands at low and high spins by new gamma-ray transitions. These transitions, as it turns out, correspond to the rotational frequencies where the principal superdeformed gaps (Z=66,N=86) close giving rise to up- or down-bending mechanisms. This enables to attribute the underlying theoretical configurations with much higher confidence as compared to the previous identifications. Five new SD bands have been discovered, three of them assigned to the Tb-152 and the two others to the Tb-151 nuclei. Nuclear mean-field calculations have been used to interpret the structure of known SD bands as well as of the new ones in terms of nucleonic configurations.

Eccentricity fluctuations from the color glass condensate in ultrarelativistic heavy ion collisions

In this Rapid Communication, we determine the fluctuations of the initial eccentricity in heavy-ion collisions caused by fluctuations of the nucleon configurations. This is done via a Monte Carlo implementation of a color glass condensate ${k}_{t}$-factorization approach. The eccentricity fluctuations are found to nearly saturate elliptic flow fluctuations measured recently at RHIC. Extrapolations to LHC energies are shown.

Spin and parity determinations of excited 15N based on polarized and unpolarized 12C(7Li, α)15N reaction data at Elab = 34 MeV

From an experiment conducted at the Florida State University Accelerator Laboratory with a 34MeV polarized 7Li beam bombarding a 12C target, we have obtained angular distributions and analyzing powers for states of 15N up to 20MeV in excitation energy. This study not only offers the possibility to assign spin and parity to several states in 15N, but also serves to obtain nuclear potential parameters used in Distorted Wave Born (DWBA) and Coupled Channel Born (CCBA) Approximations to generate theoretical angular distributions and vector analyzing powers that give the best description of the experimental data. Under the assumption that the reaction mechanism is a three nucleon transfer, the determination of shell model nucleonic configurations and spectroscopic factors is possible for the 15N states studied.

High-Kisomers and rotational structures inW174

High-spin states in $^{174}\mathrm{W}$ (Z = 74) have been populated using the reaction $^{128}\mathrm{Te}$($^{50}\mathrm{Ti}$, 4n)$^{174}\mathrm{W}$ at beam energies of 215 and 225 MeV. The Gammasphere array was used to detect the \ensuremath{\gamma} rays emitted by the evaporation residues. Four previously known collective band structures have been extended, and 16 new rotational sequences observed. Two are built upon isomeric states, one corresponding to a two-quasiparticle K = 8 isomer, the other to a four-quasiparticle K = 12 isomer, with the latter exhibiting strong K-violating $\ensuremath{\Delta}K=12$ decays to the ground state band. Nucleonic configurations for the two- and four-quasiparticle excitations are proposed, and Woods-Saxon cranking calculations are presented to understand the rotational structures. Decay mechanisms of multi-quasiparticle K isomers are discussed in terms of the prevalent phenomenological models, with special emphasis on \ensuremath{\gamma}-tunneling calculations. Surprisingly, the latter underpredict the decay hindrance for the K = 12 isomer by three orders of magnitude, unlike all other isomer decays in this mass region.

Solution of the Skyrme–Hartree–Fock–Bogolyubov equations in the Cartesian deformed harmonic-oscillator basis. (V) HFODD(v2.08k)

Solution of the Skyrme–Hartree–Fock–Bogolyubov equations in the Cartesian deformed harmonic-oscillator basis. (V) HFODD(v2.08k)

Nucleon knockout experiments and configuration mixing in nuclei

The importance of nucleon knockout experiments for a deeper understanding of nucleon properties in the nuclear medium is clarified. Results of (e, e′p) experiments yield a clear picture of the importance of configuration mixing at all energy scales. A comparison of experimental data with Green's function calculations indicates that a quantitative understanding of the properties of protons in the nuclear ground state is within reach. The latter feature makes nuclear physics the first branch of physics where such an understanding of the in-medium properties of strongly interacting constituents has been accomplished.

Solution of the Skyrme–Hartree–Fock–Bogolyubov equations in the Cartesian deformed harmonic-oscillator basis. (IV) HFODD (v2.08i): a new version of the program

We describe the new version (v2.07f) of the code HFODD which solves the nuclear Skyrme-Hartree-Fock or Skyrme-Hartree-Fock-Bogolyubov problem by using the Cartesian deformed harmonic-oscillator basis. In the new version, all symmetries can be broken, which allows for calculations with angular frequency and angular momentum tilted with respect to the mass distribution. The new version contains an interface to the LAPACK subroutine ZHPEVX.

Shell model description of isotope shifts in calcium

Isotope shifts in the nuclear charge radius of even and odd calcium isotopes are calculated within the nuclear shell model. The model space includes all configurations of nucleons in the $2s, 1d_{3/2}, 1f_{7/2}, {\rm and} ~2p_{3/2}$ orbits. The shell model describes well the energies of the intruder states in Sc and Ca, as well as the energies of the low-lying $2^+$ and $3^-$ states in the even Ca isotopes. The characteristic features of the isotope shifts, the parabolic dependence on $A$ and the prominent odd-even staggering, are well reproduced by the model. These features are related to the partial breakdown of the $Z = 20$ shell closure caused by promotion, due to the neutron-proton interaction, of the $ds$ shell protons into the $fp$ shell.

Different nucleon-nucleon cross sections and multifragmentation

We present a systematic study of the dependence of the fragment production on the nucleon-nucleon cross section using the quantum molecular dynamics model as an event generator. We employ constant energy-dependent and in-medium cross sections. In our analysis, fragments are formed using a minimum spanning tree description. The fragment distribution with different cross sections at low energy is nearly the same. At higher energies, different nucleon-nucleon (NN) cross sections have small effects on fragment production for central collisions, whereas the fragment production is strongly influenced at semicentral and peripheral collisions. A larger NN cross section results in more intermediate mass fragments at peripheral collisions with a shift of the peak towards larger impact parameters. As a result, the rapidity distribution of fragments and the fragment flow is also affected by the choice of the cross section. This influence is reduced if fragments are constructed with a sophisticated algorithm such as the simulated annealing clusterization algorithm which searches for the most bound configuration of nucleons and fragments.

Charge exchange reaction of the neutron-halo nucleus 11Li

Charge exchange reactions of the 11Li nucleus have been measured by means of the inverse kinematics on proton and deuteron targets at 63 A MeV. The isobaric analog state of the 11Li nucleus has been found at E x( 11Be) = 21.14 ± 0.03 MeV with the width Γ = 0.25 −0.1 +0.2 MeV. Neutron halo effects and the configuration of halo nucleons are discussed.

Gamma n--> pi -p process in 4He and 16O.

Nuclear transparencies for the fundamental process {gamma}{ital n}{r_arrow}{pi}{sup {minus}}{ital p} on {sup 4}He and {sup 16}O have been calculated using nucleon configurations obtained from realistic ground-state wave functions by the Monte Carlo method. Comparisons between nuclear transparency results using nucleon configurations and the correlated Glauber approximation are made in the case of ({ital e},{ital e}{sup {prime}}{ital p}) on {sup 4}He and {sup 16}O. Furthermore, nuclear transparencies for the {gamma}{ital n}{r_arrow}{pi}{sup {minus}}{ital p} and ({ital e},{ital e}{sup {prime}}{ital p}) processes have been calculated including a color transparency effect. {copyright} {ital 1996 The American Physical Society.}

Mean fields in colliding nuclear matter

Abstract The momentum-space configuration of the participant nucleons in the early stage of heavy-ion collisions can be described by a colliding nuclear matter configuration, i.e. by two Lorentz elongated Fermi ellipsoids. We introduce this configuration in the framework of the Hartree approximation of the σω-model. The configuration and the mean fields are constructed self-consistently, respecting the Pauli principle for interpenetrating ellipsoids at low relative velocity in a covariant and density conserving manner. In a second step we approximately construct mean fields for these configurations in the context of Brueckner theory. To do this we parametrize the real part of the self-energy of relativistic Brueckner calculations for equilibrated nuclear matter (one-Fermi sphere) in a Hartree scheme to obtain momentum- and density-dependent coupling parameters. With these we calculate the scalar and vector self-energy of a nucleon in colliding nuclear matter consistently with the configuration. The mean self-energy components show strong correlation and exchange effects. The results can be used to improve relativistic transport calculations for heavy-ion collisions.

Magnetic Moments of Nuclei and g Factors for Baryons and Quarks in SU2 Quantum Universal Enveloping Algebra

The quenching phenomena on the magnetic moments of odd A !)uclei have been studied by assuming the shell model configuration of nucleons and SU2 quantum universal enveloping (QUE) algebra. In order to test a q deformation observed from this analysis is universal or not, we have analyzed the magnetic moments of odd·odd nuclei in the same approach, by taking the experimental data of relevant pair of odd A nuclei close in nature as inputs for the chosen odd-odd one. The additional and reasonable values of q deformation found there clearly indicate that the QUE­ algebraic angular-momentum coupling rule is realized in nature at least for the composite system. It is pointed out that the L1 (1232) will contribute so as to smooth out the q to a common finite-ranged value of it.

Ternary fission of neutron induced uranium fissioning isomers

Spontaneously fissioning isomers (SFI) of uranium were produced in 236, 238U(n,n') reactions at 4.5 MeV mean neutron energy. A pulsed beam electrostatic accelerator was used and a time analysis of fission events was applied. Fission fragments were detected by a scintillation method, and long-range fission particles were detected by an ionization technique. Relative fission probabilities through the SFI state for both the nuclei were determined as (1.30 ±.01).10 −4 in 236 U and (1.48 ± 02) . 10 −4 in 238U case. The SFI half-lives were determined as 121 ± 2 ns and 267 ± 13 ns respectively. As a result of uranium SFI ternary fission study it was observed that one ternary per 163 ± 44 binary fissions of 236mfu and one ternary per 49 ± 14 binary fissions of 238mfU took place. These figures seem to be rather high as compared with nonisomeric ternary fission probability data, and tentative effect of a particular nucleon configuration in the uranium SFI is supposed.

Search for correlations between prolate-shape collective and oblate-shape non-collective nuclear rotation: High-spin states in 159,160Yb

High-spin states of 159,160Yb have been studied using the escape-suppressed array TESSA 2. Extensions of yrast and lateral bands have been found up to I ~ 40. Experimental data suggest strong correlations between maximum alignment configurations of the valence nucleons and related collective states. Theoretical analysis fully supports the idea of prolate-collective versus oblate-noncollective correlations. Band termination interpretation is discussed.