Nuclear Physics A最新文献

The entanglement entropy of s and d bosons in the framework of Interacting Boson Model -1 (IBM-1) has been obtained using consistent-Q formalism and semiclassical approximation. This has been possible by using Schmidt decomposition and expressing s and d bosons entanglement entropy in terms of Schmidt numbers. In this research, a simple method in the framework of IBM-1 has been presented for deriving the entanglement entropy in the Casten triangle. The results indicated that the entanglement entropy is sensitive to the shape-phase transition in the various regions of the Casten triangle. It was demonstrated that the entanglement entropy of s and d bosons in the semiclassical approximation depends only on the values of the deformation parameter (β) and is independent of the angular parameter (γ). Also, the entanglement entropy between s and d bosons reaches its maximum value in the $O\left(6\right)$ limit, while it decreases in the $SU\left(3\right)$ limit, and reaches zero in the $U\left(5\right)$ limit. Based on the results obtained via Schmidt decomposition, it is shown that the probability distribution functions of the number of s bosons in IBM-1 are the binomial distributions. For $N_B\gg 1$, it was proved that the distribution function in the $SU\left(3\right)$, $O\left(6\right)$ and $\overline{SU\left(3\right)}$ limits is the Gaussian, and in the $U\left(5\right)$ limit is the Poissonian.

Simultaneous measurements of the relative fission fragment charge and mass yield distributions have been performed for the even-even fission fragments produced from the reaction, ²³⁵U($n_{th}$,f). The measurements have been carried out using the conventional fission fragment spectroscopic technique. The extracted results are interpreted on the basis of the Multi-Modal Random Neck Rupture Model (MM-RNRM). The results from the analysis bring out the necessary experimental evidence for the influence of the deformed proton shell closures at Z = 52 and ∼ 56 along with the neutron shell closures at N = 82 (spherical) and 88 (deformed) in controlling the respective S1 and S2 fission modes occurring in the heavier group of asymmetric fission fragments. The new findings from the present investigation provide the crucial inputs for understanding the features of different fission modes that persist in the low-energy fission dynamics of the lighter actinides. The pair wise neutron multiplicity distribution profiles for the five correlated fission fragment pairs have been presented, and the corresponding extracted neutron multiplicity values are also reported.

In this study, we investigate photon-photon scattering in ultra-peripheral heavy ion collisions (UPCs). We start by deriving an effective Lagrangian from first principles and then apply factorization techniques from Soft-Collinear effective theory (SCET). This approach allows us to decompose the photon-photon scattering cross-section into two primary factors: the generalized transverse momentum distributions (GTMDs) and the hard scattering amplitude. We further analyze the emission of soft photons by final state leptons, incorporating a soft function into the cross section through an evolution method. Our analysis yields detailed predictions for observable angular correlations among the final state leptons. Specifically, we calculate the angular correlations characterized by the azimuthal parameters $〈\cos 2\varphi 〉$ and $〈\cos 4\varphi 〉$, highlighting the influence of initial photons polarization and recoil effects from final state soft photons.

We present the gluon generalized TMDs for non-zero skewness and Wigner distributions in the boost invariant longitudinal space. The boost-invariant longitudinal space is defined as $\sigma =\frac{1}{2}{b}^{-}{\Delta }^{+}$ and is conjugate to the skewness variable ξ. We use the dressed quark model, where a high-energetic quark is dressed by a gluon. This two-particle system has the advantage of addressing both the gluon and the quark sectors. The different contributions in Wigner distributions coming from different polarization of gluon and the dressed quark system are investigated.

In this work, we are presenting a new database of astrophysical interest, based on calculations performed with the nuclear reaction code TALYS. Four quantities are systematically calculated for over 8000 nuclides: cross sections, reaction rates, Maxwellian Averaged Cross Sections (or MACS) at 30 keV and partition functions. For cross sections and reaction rates, nine reactions are considered, induced by neutron, proton or alpha. The main complement of this database compared to existing ones is that the impact of reaction models (e.g. level density, gamma strength function, and optical model) is estimated by varying 9 different models, and by proposing calculated values for each of them, together with averages, standard deviations and other statistical quantities. This new database, called TENDL-astro, version 2023, is available online (https://tendl.web.psi.ch/tendl_2023/astro/astro.html) and linked to the well-known TENDL database, used in a variety of applications.

We re-examine the nuclear structure properties of waiting point nuclei around A ∼ 70 using the interacting boson model-1 (IBM-1) and the relativistic mean field (RMF) model. Effective density-dependent meson-exchange functional (DD-ME2) and density-dependent point-coupling functional (DD-PC1) were used for the RMF calculations. We calculated the energy levels, the geometric shapes, binding and separation energies of nucleons and quadrupole deformation parameters (${\beta }_2$). The shape co-existence phenomena in A ∼ 70 nuclei (⁶⁸Se, ⁷⁰Se, ⁷⁰Br, ⁷⁰Kr, ⁷²Kr, ⁷⁴Kr, ⁷⁴Rb and ⁷⁴Sr) was later investigated. Spherical and deformed shapes of the selected waiting point nuclei were computed using the IBM-1 and RMF models, respectively. The proton-neutron quasiparticle random phase approximation (pn-QRPA) model was used to calculate β-decay properties (Gamow-Teller strength distributions, β-decay half-lives and branching ratios) of selected nuclei as a function of ${\beta }_2$. The results revealed a significant variation in calculated half-lives and Gamow-Teller strength distributions as the shape parameter was changed. The ${\beta }_2$ computed via DD-ME2 functional resulted in half-lives in best agreement with the measured data.

The AGS equations for rearrangement transition operators in the three-particle problem are turned into a set of effective multi-channel two-body equations using the pseudo-state discretization of the two-particle resolvent. The resulting effective equations are LS-type integral equations in the spectator degrees of freedom, much like the LS equations of multichannel inelastic scattering. In particular, the effective potential matrix is real, energy-independent and non-singular, while the propagator matrix has only simple poles. Difficulties associated with the moving singularities of the effective potential matrix in the usual separable-T approach to AGS equations are avoided. After regularization of the kernel via subtraction procedures well known from two-particle scattering, the set of coupled LS-type equations in the spectator momenta are solved rather straightforwardly by the Nyström method. Solutions of effective two-body equations are then used to calculate the breakup amplitudes using the well-known relationship between rearrangement and breakup amplitudes. Calculations using a local momentum-space basis on a benchmark model of the n+d collision show that rather accurate results for elastic and breakup amplitudes can be obtained with rather small bases.

In the present work, we have predicted the half-lives for the ${\beta }^{-}$ decay for higher forbidden unique transitions in the mass range of nuclei from A = 40-138. For these transitions, the experimental data for half-lives are not available except for a few cases. The calculations for half-lives are performed within the framework of the nuclear shell model (SM). We have used the effective interactions sdpf-mu, gxpf1a, gwbxg, G-matrix, snet, sn100pn, and jj56pnb to perform the SM calculations in different mass regions. A comprehensive discussion has been made between the SM predicted half-lives and the scaled half-lives from proton-neutron quasiparticle random-phase approximation (pnQRPA). The results of the present study will be useful to plan new experiments to measure half-lives for these higher forbidden unique ${\beta }^{-}$ transitions.

A potential model is applied for the analysis of the astrophysical direct nuclear capture process ¹⁶O(p,${\gamma )}^{17}$F. The phase-equivalent potentials of the Woods-Saxon form for the p${-}^{16}$O interaction are examined which reproduce the binding energies and the empirical values of ANC for the ¹⁷F(5/2⁺) ground and ¹⁷F(1/2⁺) ($E^{⁎}$=0.495 MeV) excited bound states from different sources. The best description of the experimental data for the astrophysical S factor is obtained within the potential model which yields the ANC values of 1.043 fm^−1/2 and 75.484 fm^−1/2 for the ¹⁷F($5/2^{+}$) ground and ¹⁷F($1/2^{+}$) excited bound states, respectively. The zero-energy astrophysical factor $S\left(0\right)=9.321$ KeV b is obtained by using the asymptotic expansion method of D. Baye. The calculated reaction rates within the region up to 10¹⁰ K are in good agreement with those from the R-matrix approach and the hierarchical Bayesian model in both absolute values and temperature dependence.

The sharp shape phase changes with increasing N of the A = 100–110 Mo isotopes, as associated with the deformed N = 60 shape turning point of the structure, are studied. In terms of the shape change with proton number Z, the Mo isotopes lie in between the Sr, Zr and Ru, Pd chain of isotopes. We have analyzed the special spectral features of these Mo isotopes through the energy level structures, in ground state bands, the K^π = 2⁺ and K^π = 4⁺ excited bands empirically. The unique features of the association of triaxiality, along with the rotational bands, are well illustrated. The interacting boson model (IBM-1) is used to reproduce the level structures of the Mo isotopes. An in-depth analysis of the spectral features of the Mo isotopes is presented. There is emphasis on the physics of the shape transitions.