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Spontaneous fission of 252Cf and fusion-induced fission of 250Cf are investigated within a multi-dimensional Langevin model. The potential-energy surface is calculated in the macroscopic-microscopic LSD+Yukawa-folded approach using the four-dimensional Fourier-over-Spheroid shape parametrization. The dynamical evolution described by the Langevin equation is coupled to neutron evaporation, thereby allowing for the possibility of multi-chance fission. Charge equilibration and excitation-energy sharing between the fragments emerging at scission are evaluated, and their de-excitation is finally computed. The correlation between various observables, particularly the isotopic properties of the fragments, is discussed and compared with the experiment whenever available. The theoretical predictions are generally in good agreement with the data., Comment: 13 pages, 16 figures

A rapidly converging 4-dimensional Fourier shape parametrization is used to model the fission process of heavy nuclei. Potential energy landscapes are computed within the macroscopic-microscopic approach, on top of which the multi-dimensional Langevin equation is solved to describe the fission dynamics. Charge equilibration at scission and de-excitation by neutron evaporation of the primary fragments after scission is investigated. The model describes various observables, including fission-fragment mass, charge, and kinetic energy yields, as well as post-scission neutron multiplicities and, most importantly, their correlations, which are crucial to unravel the complexity of the fission process. The parameters of the dynamical model were tuned to reproduce experimental data obtained from thermal neutron-induced fission of $^{235}$U, which allows us to discuss the transition from asymmetric to symmetric fission along the Fm isotopic chain., Comment: Presented at the Mazurian Lakes Conference on Physics, 2023, Poland

We propose a new, rapidly convergent, the so-called Fourier over Spheroid (FoS), shape parametrization to model fission of heavy nuclei. Four collective coordinates are used to characterize the shape of the fissioning system, being its elongation, left-right asymmetry, neck size, and non-axiality. The potential energy landscape is computed within the macroscopic-microscopic approach, on the top of which the multi-dimensional Langevin equation is solved to describe the dynamics. Charge equilibration at scission and de-excitation of the primary fragments after scission are further considered. The model gives access to a wide variety of observables, including fission fragments mass, charge, and kinetic energy yields, fragment mean N/Z and post-scission neutron multiplicities, and importantly, their correlations. The latter are crucial to unravel the complexity of the fission process. The parameters of the model were tuned to reproduce experimental observation from thermal neutron-induced fission of 235U, and next used to discuss the transition from the asymmetric to symmetric fission along the Fm isotopic chain., Comment: 15th pages, 18 figures

Potential energy surfaces and fission barriers of superheavy nuclei are analyzed in the macroscopic-microscopic model. The Lublin-Strasbourg Drop (LSD) is used to obtain the macroscopic part of the energy, whereas the shell and pairing energy corrections are evaluated using the Yukawa-folded potential. A standard flooding technique has been used to determine the barrier heights. It was shown the Fourier shape parametrization containing only three deformation parameters reproduces well the nuclear shapes of nuclei on their way to fission. In addition, the non-axial degree of freedom is taken into account to describe better the form of nuclei around the ground state and in the saddles region. Apart from the symmetric fission valley, a new very asymmetric fission mode is predicted in most superheavy nuclei. The fission fragment mass distributions of considered nuclei are obtained by solving the 3D Langevin equations., Comment: 20 pages, 17 figures

In our previous work, based on the $SU(6)$ spin-flavor wave function, we regard $\Lambda$ and $p$ as composed of different quark-diquark configurations and established the Bethe-Salpeter (BS) equations of configurations for quark and scalar diquark. In our present work, we apply this model to calculate the form factors of the semileptonic transitions $\Lambda_b\rightarrow\Lambda l^+l^-$ $(l=\mu,e,\tau)$ and $\Lambda_b\rightarrow p l\bar{\nu}$ within the Standard Model (SM). The decay $\Lambda_b\rightarrow\Lambda \mu^+\mu^-$ is especially interesting since it has been measured in CDF and LHCb Collaborations and this rare decay is very sensitive to new physics effects. The decay $\Lambda_b\rightarrow p l\bar{\nu}$ is a promising mode for the measurement of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{ub}|$ at the Large Hadron Collider. In our calculations, depending on the ranges of the parameters in the model including the diquark mass and the interaction strength between the quark and the diquark in the kernel of the BS equation, we find that the branching ratio of $\Lambda_b\rightarrow\Lambda\mu^+\mu^-$ in our model is consistent with the experimental data and the current experimental results from LHCb agree with the differential branching ratio of $\Lambda_b\rightarrow\Lambda\mu^+\mu^-$ from our calculation except at the lager momentum transfer region. This indicates that there is still room for possible new physics effects. We also give comparisions of the total branching ratios of $\Lambda_b\rightarrow\Lambda l^+l^-$ and $\Lambda_b\rightarrow p l\bar{\nu}$ with those given by other phenomenological methods.