The European Physical Journal A最新文献

The mechanism of antiproton–nucleus annihilation at rest is not fully understood, despite substantial previous experimental and theoretical work. In this study we used slow extracted antiprotons from the ASACUSA apparatus at CERN to measure the charged particle multiplicities and their energy deposits from antiproton annihilations at rest on three different nuclei: carbon, molybdenum and gold. The results are compared with predictions from different models in the simulation tools Geant4 and FLUKA. A model that accounts for all the observed features is still missing, as well as measurements at low energies, to validate such models.

Proton radioactivity is an exotic decay mode of proton-rich nuclei far from the (beta )-stability line and shares the similar decay mechanism theory of barrier penetration as (alpha ) decay. In present work, we extend the Hatsukawa formula (Hatsukawa et al. in Phys Rev C 42:674, 1990) for (alpha ) decay to proton radioactivity and propose an empirical formula for evaluating the proton radioactivity half-lives of proton nuclei with Z  >  68. Using this formula, we systematically calculate the proton radioactivity half-lives of 33 spherical proton emitters with the corresponding root-mean-square (rms) deviation being 0.391. It is found that the calculated half-lives can reproduce the experimental data well. Moreover, we extend this formula to predict the proton radioactivity half-lives of 18 spherical proton emitters, whose proton radioactivity is energetically allowed or observed but not yet quantified. For comparison, unified fission model (UFM), Coulomb potential and proximity potential model (CPPM), universal decay law for proton emission (UDLP) and new Geiger-Nuttall law (NG-N) are also used. All the predictions are basically consistent with each other.

This study investigates the prompt fission neutron (PFN) multiplicity distribution in the spontaneous fission (SF) of (^{244})Fm. Experimental data were obtained using the complete fusion reaction (^{206})Pb((^{40})Ar,2n)(^{244})Fm, obtaining a mean of (3.6 pm 0.1) emitted neutrons per SF event. The symmetry of the PFN multiplicity distribution suggests no significant influence of additional fission modes, aligning with theoretical predictions that indicate the dominance of the standard fission mode. At the same time, comparison with neighboring isotopes points at a possible additional fission mode in (^{246})Fm.

The study of fission yields has a major impact on the characterization and understanding of the fission process and its applications. Mass yield evaluation represents a key element in order to perform the best estimation of independent and cumulative fission product yields. Today, the lack of analysis-based correlation matrix between the different fission observables induces many inconsistencies in the evaluations. In particular, the mass yield uncertainties are drastically overestimated in comparison to chain yields while these two quantities only differ from the emission of delayed neutrons. In this work, a new consistent process of mass yield evaluation is proposed taking into account the description of the covariance matrix. For (^{235}text {U(n}_{text {th}}text {,f)}) mass yields, existing data cover a large range of produced masses which makes it possible to propose an evaluation of mass yields independently of any model with a precision closed to (1.5%) for the high yields. This new precision brings the possibility to discuss the origin of the structures in the post-neutron mass yields, in particular the consistency with the pre-neutron mass yields and the prompt neutron multiplicity per mass. The work is the first part of the (^{235}text {U(n}_{text {th}}text {,f)}) thermal neutron induced fission yield evaluation which will be included in the new JEFF-4 library.

Neutron transfer cross sections for ⁷Li+²⁰⁵Tl system were measured near Coulomb barrier energies using online (gamma )-ray detection technique. One neutron stripping, two neutron stripping, and one neutron pickup cross sections have been extracted and are compared with the Coupled Reaction Channel (CRC) calculations. The systematics of one and two neutron stripping and pickup cross sections with a ⁷Li projectile on several targets show an approximate universal behaviour. A comparison of integrated neutron transfer cross sections with complete and incomplete fusion cross sections available with ⁷Li projectile is presented to understand the systematic behaviour. The neutron transfer along with cumulative sum of complete and incomplete fusion was found to explain the estimated reaction cross section in ⁷Li+²⁰⁵Tl system.

For the even nuclei of (^{204-208})Rn, (^{214-218})Ra and (^{232-234})U, the simultaneous description of charge distribution and total kinetic energy are studied within the scission-point model. The calculated data are compared with experimental data from the literature. Correlations between these observables and other quantities of interest are analysed.

The total reaction cross sections for systems with medium–heavy-mass range targets of Sn isotopes including ¹¹⁶Sn, ¹¹⁸Sn, ¹²⁰Sn, and ¹²⁴Sn, along with different projectiles ranging from tightly bound to weakly bound and halo, were taken from the literature and compared by reducing them to eliminate trivial effects due to different sizes and different Coulomb barriers. In addition, for all the systems considered, one-channel calculations accounting only for fusion were performed to study the quantitative effect of the direct reaction channels on the total reaction cross section.

The resonant (^{14})N+(alpha ) particle scattering was studied in the (^{18})F excitation region from 6.5 to 9 MeV at Astana cyclotron using the TTIK approach. The excitation functions for the elastic (^{14})N+(alpha ) scattering were analyzed in the framework of R matrix calculations. The observed strong alpha cluster structure in (^{18})F is compared with that in (^{18})O. While the general agreement of the structure in both nuclei is confirmed, a striking difference for l = 4 resonances is found. The experimental results are compared with configuration interaction calculations.

Silicon isotopic ratios measured in meteoritic presolar grains can provide useful information about the nucleosynthesis origin of these isotopes if the rates of nuclear reactions responsible for their production are known. One of the key reactions determining the Si isotopic abundances is (^{29})Si(p,(gamma ))(^{30})P. Its reaction rate is not known with sufficient precision due in part to some ambiguous resonance strength values. In the present work, the strength of the (E_textrm{p}) = 416.9 keV resonance has been measured with high precision using the activation technique. The new strength of (omega gamma = 219 pm ) 16 meV can be used in updated reaction rate estimations and astrophysical models.

We present a computation of triply-heavy baryons on a quantum computer, employing the Cornell quark model in line with the earlier quarkonium work of Gallimore and Liao. These baryons are some of the most interesting Standard Model particles which have not yet been detected, as they bear on the short range (colour) behaviour of the nuclear force. The spectrum here obtained is compatible with predictions from earlier works, with our uncertainty dominated by traditional few-body approximations (size of the variational basis, center of mass recoil, parameter estimation...) and not by the statistical error from the quantum computer (deployed here as a small diagonalizer), which turns out to be negligible with respect to the other sources of uncertainty, at least in the present unsophisticated few-body approximation. We have also substituted one or more heavy quarks for strange quarks.