The European Physical Journal A最新文献

The absorbing boundary conditions method is applied in the microscopic Bloch–Brink cluster model using the generator coordinate method to study the resonance states of (^8textrm{Be}). A complex absorbing potential is introduced into the Hamiltonian, equivalent to the absorbing kernels added to the Hill-Wheeler equation. The (0^{+}), (2^{+}), and (4^{+}) states of (^{8}textrm{Be}) are analyzed for their corresponding energies and widths. The obtained results are consistent with those of the algebraic version of the resonating group method. This work is helpful in demonstrating the efficiency of the absorbing boundary conditions method for addressing nuclear cluster resonance problems within the framework of the generator coordinate method.

Excited states above the (9^+) isomer in the odd-odd N = Z nucleus (^{66})As were studied by employing the (^{40})Ca((^{28})Si, pn) fusion-evaporation reaction at the Accelerator Laboratory of the University of Jyväskylä, Finland. A key method in this study was the use of conversion electrons emitted in the de-excitation of the isomeric state in (^{66})As as a tag for prompt (gamma ) rays. Several new states have been added to the (^{66})As level scheme, which was extended up to a tentative spin of 23(hbar ). The previously reported even-spin yrast band has been reassigned to have odd spin values. The odd-spin states above the (9^+) isomer are compared with shell-model calculations using the jj44b and JUN45 interactions. Additionally, the recoil-(beta ) tagging efficiency of the recently developed scintillator detector named Tuike has been determined experimentally for the first time.

The possibility of wobbling mode in the A (approx ) 80 mass region is investigated by using the constrained triaxial covariant density functional theory and quantum particle rotor model for rubidium isotopes. Several states with the obvious triaxial deformation and high-j particle configuration are obtained in (^{79,81,83,85})Rb, which are suitable for establishing the wobbling mode. Taking the nucleus (^{81})Rb as an example, the available experimental energy spectrum with the (pi )g(_{9/2}) configuration is described well. The decreased energy difference between the partner bands, the enhanced (B(E2)_{out})/(B(E2)_{in}) values, the angular momentum components and the azimuthal plots indicate that (^{81})Rb can be transverse wobbling candidate. The present work provides a promising basis for future experimental research on the wobbling mode in the A (approx ) 80 mass region.

Inclusive spectra of the kaons produced in ArSc collisions as functions of their transverse momentum (p_T) at mid-rapidity have been calculated within the approach based on the assumption of the similarity of inclusive spectra of the hadrons produced in nucleus–nucleus collisions at their small transverse momenta in the mid-rapidity region taking into account the quark-gluon dynamics in nucleon–nucleon interactions. This article gives a satisfactory description of NA61/SHINE data on (p_T)-spectra of the (K^pm ) mesons produced in ArSc collisions at the mid-rapidity ((ysimeq ) 0).

The even-odd staggering in fission fragments yield distributions is an important observable to address the role of intrinsic excitations in the fission process. However, its computation as a function of the fragment split is an ill-posed problem that is usually solved through certain assumptions. Arguably, the most widely used method for its computation is the log-third-difference method, which assumes an underlying local Gaussian distribution. Experimental data of the even-odd effect show sharp features and peaks that are a challenge for the log-third difference method (or any method for that matter). This paper presents a detailed study of the performance of the log-third-difference method and describes three strategies for improving the precision and accuracy around these sharp features. The best results are obtained with an iterative application of the method and with the use of a multi-Gaussian fit. A hybrid process combining both corrections is also described and applied to real data. In regions with a smooth behaviour, the direct application of the log-third-difference method remains the best option.

The radiation damage of 21 (upmu )m thick self-biased epitaxial (varDelta E) detectors were tested as a function of fluence of 90 MeV (^{14})N ions. Technology of production and technique of measurements of (varDelta E) detectors were described. A new technique of soldering contact to thin detector is shown. In the present work the 21 (upmu )m thick self-biased detectors marked as d4 and d5 show proper operation with the fluence about 4(cdot )10(^{15}) (hbox {ions/cm}^{2}) and the fluence about 8(cdot )10(^{15}) (hbox {ions/cm}^{2}), respectively. The charge collection efficiency of thin d5 (varDelta E) detector was increased about double at fluence about 8(cdot )10(^{15}) (hbox {ions/cm}^{2}). The charge collection efficiency of thin d4 (varDelta E) detector was increased about 35(%) at fluence about 4(cdot )10(^{15}) (hbox {ions/cm}^{2}) followed decrease about 70(%) of detector counting rate registration from fluence 9.1(cdot )10(^{15}) (hbox {ions/cm}^{2}) to fluence about 5(cdot )10(^{16}) (hbox {ions/cm}^{2}) due to partially removing of Al evaporated contact from detector surface as an effect of heavy ion irradiation. Increase of charge collection efficiency of thin self-biased detectors manufactured by the low-temperature technique was probably produced by increasing of build-in potential as an effect of activate carrier concentration of boron ions in epitaxial layer by heavy ion irradiation.

A new (9^-) isomer has been identified in odd-odd nuclide, (^{92})Nb which was populated using the reaction (^{80})Se((^{18})O, p5n)(^{92})Nb at a beam energy of 99 MeV. The (gamma -gamma ) coincidences were measured using Indian National Gamma Array (INGA). The previously reported isomeric state at (11^-) was revisited and the half-life is measured to be 103.6(32) ns. The half-life of the newly observed 9(^- ) isomer in (^{92})Nb has been measured to be 35.8(23) ns for the first time. The transition probability (textit{B}(textit{E})2) has been determined for the isomeric state. The isomeric structure has been interpreted as a four-quasiparticle excitation, consisting of three protons and one neutron, using large-scale shell model calculations.

Giant Resonances are, with nuclear rotations, the most evident expression of collectivity in finite nuclei. These two categories of excitations, however, are traditionally described within different formal schemes, such that vibrational and rotational degrees of freedom are separately treated and coupling effects between those are often neglected. The present work puts forward an approach aiming at a consistent treatment of vibrations and rotations. Specifically, this paper is the last in a series of four dedicated to the investigation of the giant monopole resonance in doubly open-shell nuclei via the ab initio Projected Generator Coordinate Method (PGCM). The present focus is on the treatment and impact of angular momentum restoration within such calculations. The PGCM being based on the use of deformed mean-field states, the angular-momentum restoration is performed when solving the secular equation to extract vibrational excitations. In this context, it is shown that performing the angular momentum restoration only after solving the secular equation contaminates the monopole response with an unphysical coupling to the rotational motion, as was also shown recently for (quasi-particle) random phase approximation calculations based on a deformed reference state. Eventually, the present work based on the PGCM confirms that an a priori angular momentum restoration is necessary to handle consistently both collective motions at the same time. This further pleads in favor of implementing the full-fledged projected (quasi-particle) random phase approximation in the future.

We present a comparison of directed and elliptic flow data by the FOPI collaboration in Au–Au, Xe–CsI, and Ni–Ni collisions at beam kinetic energies from 0.25 to 1.5 GeV per nucleon to simulations using the SMASH hadronic transport model. The Equation of State is parameterized as a function of nuclear density and momentum dependent potentials are newly introduced in SMASH. With a statistical analysis, we show that within the present status of the SMASH transport model, the collective flow data at lower energies is in the best agreement with a soft momentum dependent potential, while the elliptic flow at higher energies requires a harder momentum dependent equation of state.