Nuclear Physics A最新文献

The origin of the neutron skin thickness, measured by the CREX and PREX collaborations as thin for ⁴⁰Ca and thick for ²⁸Pb, remains a mystery. We investigate the effects of tensor and nonlinear isovector–isoscalar terms in a relativistic mean-field model (RMF) on the properties of finite nuclei and nuclear matter. Tensor couplings are crucial for better quality binding energies of finite nuclei and charge radii for relatively heavy nuclei. However, for light nuclei, the tensor terms cannot improve the compatibility of charge radius predictions by the RMF model with experimental data. We find that parameter sets with a larger nonlinear isovector–isoscalar parameter, particularly ${\eta }_{2\rho }$ = 0.028, agree better with experimental data for Δ$r_{np}$ across light, medium, and heavy isotope chains. Using PT28, we calculate Δ$r_{np}$ for ²⁰⁸Pb as 0.214 fm, J as 33.078, and L as 58.426. Δ$r_{np}$ for ²⁰⁸Pb obtained using PT28 is consistent with the PREX-II data. Moreover, the corresponding values of J and L agree with the low L constraints. Meanwhile, the canonical mass radius predicted by PT28 aligns with the mass and radius data from the NICER collaboration. The combination of tensor and nonlinear isovector–isoscalar couplings in the RMF model provides accurate predictions for finite nuclei binding energies and relatively heavy nuclei charge radii, resulting in relatively thick Δ$r_{np}$ values for ²⁰⁸Pb without substantial L values.

To understand the break-up fusion reaction dynamics, the forward recoil range distribution (FRRD) measurements of ¹²C + ¹⁶⁵Ho system at the incident projectile energy of ≈ 88 MeV has been performed. The recoil catcher activation technique followed by the off-line gamma ray spectroscopy was implemented. It is observed that the FRRD measurements of the evaporation residues (ERs) populated via xn and pxn channels have a single Guassian peak at large cumulative thickness. This is attributed to complete momentum transfer from the projectile to the target nucleus. However, in case of the FRRD measurements of the ERs populated via αxn, αpxn and 2αxn emitting channels, in addition to peak corresponding to complete momentum transfer, the Gaussian peaks at lower cumulative thicknesses are also observed. This is accredited to the breakup fusion. Moreover, the effect of projectile breakup on complete fusion cross section is also studied. The suppression in fusion cross section is observed when compared with the universal fusion function, thus indicating the breakup probability of ¹²C projectile.

Large-scale shell-model calculations have been performed for the study of two-neutrino double-beta ($2\nu \beta \beta$) decay in ⁸²Se, ⁹⁴Zr, ¹⁰⁸Cd, ¹²⁴Sn, ¹²⁸Te, ¹³⁰Te, ¹³⁶Xe, and ¹⁵⁰Nd. We have employed JUN45 interaction to calculate the nuclear matrix element (NME) for $2\nu \beta \beta$ decay in ⁸²Se. In the case of ⁹⁴Zr, the glekpn effective interaction is used. For ¹⁰⁸Cd, we have used a realistic effective interaction derived through the G-matrix approach. In the case of ¹²⁴Sn, ^128,130Te and ¹³⁶Xe, the sn100pn effective interaction is employed. For ¹⁵⁰Nd, we have used KHHE effective interaction based on holes in a ²⁰⁸Pb core. We have extracted the half-lives of these nuclei for the $2\nu \beta \beta$ decay with the help of calculated NME. Our results are consistent with the available experimental half-lives. The variation of cumulative $2\nu \beta \beta$ NME with respect to the excitation energy of the intermediate $1^{+}$ states is also shown, and in all cases, it is ensured that their values are almost saturated. In the present work we have calculated more intermediate $1^{+}$ states as much as possible in comparison to results available in the literature.

The values of the parameters ${\rho }^{pp},{\sigma }_{\text{tot}}^{pp}$ and $B^{pp}$ extracted in the region of Coulomb-nuclear interference (CNI) in the ATLAS and TOTEM experiments at energy $\sqrt{s}=13$ TeV are studied based on the general expression for the Coulomb-nuclear amplitude. Due to the significant differences between these data, we undertake both their joint analysis and the retrieval of parameter values separately for each experiment. A significant incompatibility of these parameters published by the ATLAS and TOTEM experiments is shown. This is especially noticeable in the case of ${\sigma }_{\text{tot}}$ and the situation is similar to what once happened at the TEVATRON: the values of ${\sigma }_{\text{tot}}^{ATLAS}$ with account of errors do not overlap with ${\sigma }_{\text{tot}}^{TOTEM}$.

Results of our experimental study of the ²⁴Mg${(p,\gamma )}^{25}$Al resonance reaction at E${}_p{}^{lab}=223$ keV are presented. The proton beam energy is varied from 220 to 265 keV. An evaporated Mg target with thick Ta backing is used. We remeasure a mean lifetime of $\tau ={6.04}_{-2.65}^{+3.03}$ fs for the E${}_x=2485.3$ keV level of ²⁵Al, using Doppler shift attenuation (DSA) method. Three most successfully used empirical effective interactions developed for the sd shell by Wildenthal (w), Chung-Wildenthal (cw) and Preedom-Wildenthal (pw), are utilized to calculate energy spectra, spectroscopic factors, beta decay properties, transition probabilities and the lifetime of the resonance state in ²⁵Al within the framework of nuclear shell model. The theoretical results agree reasonably well with the experimental data. However, a detailed study for each set to identify the most preferred interaction for this nucleus is performed. Calculated lifetimes using two of the interactions (w, cw) agree better with the central value of the experimental lifetime of the resonance state measured in the present work.

The (n,γ) reaction cross-section of rare earth stable fission products, such as ¹⁵²Sm, ¹⁵⁴Sm and ¹⁵⁰Nd, in the neutron energy range of 0.8 to 2 MeV, obtained from ⁷Li(p,n)⁷Be reaction, was measured by neutron activation followed by off-line gamma-ray spectrometry. Natural strontium (^natSr) has been established as a fast neutron flux monitor in this work, by measuring the ^natSr(n,γ+n,n′)⁸⁷Sr^m reaction cross-section using ¹²⁷I(n,γ)¹²⁸I as monitor reaction. The cross-section for ⁸⁶Sr(n,γ)⁸⁷Sr^m has been determined for the first time to the best of our knowledge. The excellent decay properties of ⁸⁷Sr^m and opposite energy dependence of ⁸⁶Sr(n,γ)⁸⁷Sr^m and ⁸⁷Sr(n,n′)⁸⁷Sr^m reactions makes ^natSr an excellent candidate for neutron flux monitor for wide neutron energy range. The measured (n,γ) cross-section data from the present study has been compared with the literature data, which is very limited along with large scatter in the energy range of 1–2 MeV for these nuclei. The results from the present study, clearly show a need for fresh cross-section evaluations for ¹⁵²Sm(n,γ)¹⁵³Sm. For, ¹⁵⁴Sm(n,γ)¹⁵⁵Sm and ¹⁵⁰Nd(n,γ)¹⁵¹Nd reactions, the present data align with one of the data groups among the two which can be broadly identified having difference of about more than ∼50%. The present experimental data has been compared with TALYS 1.96 theoretical model calculations based on Fermi gas level density prescriptions which shows that the cross section values are close to the experimental data at some of the neutron energies. A comparison of the data on fast neutron capture cross-section for N = 90 isotones from the present study and from the literature showed a systematic decrease in the cross-section value with increasing neutron richness of the target nucleus. The cross-section data could be scaled with neutron-proton asymmetry parameter to show a nearly linear behaviour on a logarithmic scale. The data for ¹⁵⁴Sm (N = 92) was also observed to follow the same trend.

A model-independent irreducible tensor formalism is developed to analyse $\overline{\Omega }\Omega$ production in $\overline{p}p$ collisions and its subsequent decay via the triple-strange decay process, ${\overline{\Omega }}^{+}{\Omega }^{-}\to K^{+}\overline{\Lambda }{K}^{-}\Lambda \to K^{+}\overline{p}{\pi }^{+}{K}^{-}p{\pi }^{-}$. These processes are relevant for the upcoming experiments at PANDA. We not only provide expressions for the density matrix of the $\Omega \overline{\Omega }$ system but also for the products at each stage of the decay. The Fano statistical tensors so obtained not only completely characterize the relevant final systems but also provide expressions for joint angular distributions. Finally, we show which of the Fano statistical tensors characterizing the $\overline{\Omega }\Omega$ system can be inferred from the Fano statistical tensors characterizing the final $\overline{p}p$ system, wherein we also obtain the relation between the production cross sections for $\Omega \overline{\Omega }$ and the final $p\overline{p}$ system.

We compute the equation of state (EoS) of strange quark stars (SQSs) with the MIT Bag model using density dependent bag pressure, characterized by a Gaussian distribution function. The bag pressure's density dependence is controlled by three key parameters namely the asymptotic value ($B_{as}$), $\Delta B(=B_0-B_{as})$, and β. We explore various parameter combinations ($B_{as}$, ΔB, β) that adhere to the Bodmer-Witten conjecture, a criterion for the stability of SQSs. Our primary aim is to analyze the effects of these parameter variations on the structural properties of SQSs. However we find that none of the combinations can satisfy the NICER data for PSR J0030+0451 and the constraint on tidal deformability from GW170817. So it can be emphasized that this model cannot describe reasonable SQS configurations. We also extend our work to calculate structural properties of hybrid stars (HSs). With the density dependent bag model (DDBM), these astrophysical constraints are fulfilled by the HSs configurations within a very restricted range of the three parameters. The present work is the first to constrain the parameters of DDBM for both SQS and HSs using the recent astrophysical constraints on tidal deformability from GW170817 and that on mass-radius relationship from NICER data.

The evaporation residue (ER) cross sections for the reaction ${}^{19}F{+}^{187}Re{\to }^{206}P{o}^{⁎}$ are measured, in the excitation energy range of 86.1 to 118.4 MeV. The measured cross sections are compared with that of ³⁰Si + ¹⁷⁶Yb reaction populating the same compound nucleus. Theoretical calculations are performed using the coupled - channels calculations for the capture cross sections and statistical model calculations for the ER cross sections. The dependence of quasi fission on entrance channel parameters such as charge product (Z₁Z₂), mass asymmetry (α), target deformation (${\beta }_2$) and effective fissility (${\chi }_{eff}$) are studied.

The extended optical model is used to simultaneously analyze the elastic scattering and fusion data for the weakly-bound system of ⁹Be + ¹²C in the low-energy region. Dynamic polarization potentials $U_F$, $U_D$, associated with fusion and direct couplings, respectively, are introduced. Corresponding fitting parameters leading to dispersive potentials are found, which provide good simultaneous descriptions of elastic and fusion data. The energy-dependent behavior of the polarization potentials establishes a striking difference with respect to that observed for weakly bound projectiles, including ⁹Be, on medium- and heavy-mass targets. Contrary to similar analyses made on weakly-bound systems, the real part of $U_D$ is found to be attractive in the present case. The observed behavior is discussed.