We have studied the ground state of the unbound, very neutron-rich isotope of hydrogen ${}^5\mathrm{H}$, using the ${}^6\mathrm{He}\left(d,{}^3\mathrm{He}\right){}^5\mathrm{H}$ reaction in inverse kinematics at a bombarding energy of $E\left({}^6\mathrm{He}\right)=55A$ MeV. The present results suggest a ground-state resonance energy $E_R=2.4\pm 0.3$ MeV above the ${}^3\mathrm{H}+2n$ threshold, with an intrinsic width of $\mathrm{\Gamma }=5.3\pm 0.4$ MeV in the ${}^5\mathrm{H}$ system. Both the resonance energy and width are higher than those reported in some, but not all previous studies of ${}^5\mathrm{H}$. The previously unreported ${}^6\mathrm{He}\left(d,t\right){}^5\mathrm{He}_{\mathrm{g}.\mathrm{s}.}$ reaction is observed in the same measurement, providing a check on the understanding of the response of the apparatus. The data are compared to expectations from direct two-neutron and dineutron decay. The possibility of excited states of ${}^5\mathrm{H}$ populated in this reaction is discussed using different calculations of the ${}^6\mathrm{He}\to {}^5\mathrm{H}+p$ spectroscopic overlaps from shell-model and ab initio nuclear-structure calculations.

An improved semi-empirical relationship for $\alpha$-decay half-lives is proposed by introducing a precise radius formula and an analytic expression for preformation probability. By using the improved relationship, the $\alpha$-decay half-lives of 421 nuclei are calculated. It is shown that the accuracy of this semi-empirical relationship is improved significantly compared to its predecessor. Further research shows that it also reproduces the experimental half-lives of the superheavy nuclei well. Last, with the improved formula the $\alpha$-decay half-lives of the $Z=118–121$ isotopes are predicted, which are helpful for future experiments. In addition, there is a prediction of a magic number effect at $N=184$.

In relativistic ion collisions there are excellent opportunities to produce and investigate hypernuclei. We have systematically studied the formation of hypernuclear spectator residues in peripheral heavy-ion collisions with the transport DCM and UrQMD models. The hyperon capture was calculated within the potential and coalescence approaches. We demonstrate that even at the beam energies around and lower than the threshold for producing $\mathrm{\Lambda }$ hyperons in binary nucleon-nucleon interactions a considerable amount of hypernuclei, including multistrange ones, can be produced. This is important for preparation of new experiments on hypernuclei in the wide energy range. The uncertainties of the predictions are investigated within the models, and the comparison with the strangeness production measured in experiments is also performed.

The $\varphi$-meson properties in cold nuclear matter are investigated by implementing resonant $\varphi N$ interactions as described in effective approaches including the unitarization of scattering amplitudes. Several $N^{*}$-like states are dynamically generated in these models around 2 GeV, in the vicinity of the $\varphi N$ threshold. We find that both these states and the non-resonant part of the amplitude contribute sizably to the $\varphi$ collisional self-energy at finite nuclear density. These contributions are of a similar strength as the widely studied medium effects from the $\overline{K}K$ cloud. Depending on model details (position of the resonances and strength of the coupling to $\varphi N$) we report a $\varphi$ broadening up to about 40–50 MeV, to be added to the $\varphi \to \overline{K}K$ in-medium decay width, and an attractive optical potential at threshold up to about 35 MeV at normal matter density. The $\varphi$ spectral function develops a double peak structure as a consequence of the mixing of resonance-hole modes with the $\varphi$ quasiparticle peak. The former results point in the direction of making up for missing absorption as reported in $\varphi$ nuclear production experiments.

In nuclear matter at neutron-star densities and temperatures, Cooper pairing leads to the formation of a gap in the nucleon excitation spectra resulting in exponentially strong Boltzmann suppression of many transport coefficients. Previous calculations have shown evidence that density oscillations of sufficiently large amplitude can overcome this suppression for flavor-changing $\beta$ processes, via the mechanism of “gap bridging.” We address the simplifications made in that initial work, and show that gap bridging can counteract Boltzmann suppression of neutrino emissivity for the realistic case of modified Urca processes in matter with ${}^{3}P_2$ neutron pairing.

Several recent publications claim that the proton charge rms radius resulting from the analysis of electron-scattering data restricted to low-momentum transfer agrees with the radius determined from muonic hydrogen, in contrast to the radius resulting from analyses of the full ($e,e$) data set which is 0.04 fm larger. Here we show why these publications erroneously arrive at the low radii.

Poincaré covariant definitions for the spin-dependent spectral function and for the momentum distributions within the light-front Hamiltonian dynamics are proposed for a three-fermion bound system, starting from the light-front wave function of the system. The adopted approach is based on the Bakamjian–Thomas construction of the Poincaré generators, which allows one to easily import the familiar and wide knowledge on the nuclear interaction into a light-front framework. The proposed formalism can find useful applications in refined nuclear calculations, such as those needed for evaluating the European Muon Collaboration effect or the semi-inclusive deep inelastic cross sections with polarized nuclear targets, since remarkably the light-front unpolarized momentum distribution by definition fulfills both normalization and momentum sum rules. Also shown is a straightforward generalization of the definition of the light-front spectral function to an $A$-nucleon system.

The nucleus ${}^{100}\mathrm{Ru}$ appears to be a good candidate for the E(5) critical point symmetry which describes the U(5)-SO(6) shape phase transition. To investigate this point with respect to the electromagnetic transition strengths, lifetime measurements of its yrast states have been performed using the recoil distance Doppler shift technique as well as the Doppler shift attenuation method. As a result, the lifetimes of the yrast $2^{+}$, $4^{+}$, and $8^{+}$ states were determined. The deduced transition strengths are compared to the E(5) predictions as well as to the results of excited Vampir and shell-model calculations.

The existing experimental value of the ratio $B_{4/2}\equiv B(E2;4_1^{+}\to 2_1^{+})/B(E2;2_1^{+}\to 0_1^{+})$ in ${}^{134}\mathrm{Ce}$ is less than unity, which is outside the range allowed by current collective models and is highly anomalous. In the present work, new lifetime measurements of excited states in ${}^{134}\mathrm{Ce}$ have been performed in order to clarify this discrepancy. Excited states of ${}^{134}\mathrm{Ce}$ were populated by the fusion-evaporation reaction ${}^{122}\mathrm{Sn}({}^{16}\mathrm{O},4n){}^{134}\mathrm{Ce}$. The recoil distance doppler shift method was employed, and reliable lifetimes for the $2_1^{+}, 4_1^{+}, {10}_2^{+}$, and ${12}_2^{+}$ states were derived from the differential decay curve method. The resulting $B_{4/2}$ value is larger than unity, resolving the disagreement with traditional collective models. The new experimental data is in very good agreement with the calculation in the framework of the interacting boson model. The systematic evolution in collectivity of the Ce isotopes is discussed.

A good linear correlation is found between the double-difference of charge radius $\delta R_{2p-2n}(Z,N)$ with that of quadrupole deformation data in even-even nuclei. This results in a further improved charge radius relation that holds in a precision of about $5\times {10}^{-3}$ fm. The new relation can be generalized to the reduced electric quadrupole transition probability $B\left(E2\right)$ between the first $2^{+}$ state and the $0^{+}$ ground state, and the mean lifetime $\tau$ of the first $2^{+}$ state. Same correlations are also seen in global nuclear models such as Hartree-Fock-Bogoliubov (HFB-24) and relativistic mean field (RMF); however, they are not consistent with the experimental data.

The properties of the $K$-isomer decays in the ${}^{134}\mathrm{Nd}$ and ${}^{184}\mathrm{Pt}$ nuclei have been investigated. Measurements were carried out in $e-\gamma$ and $\gamma -\gamma$ coincidence modes using electron spectrometers coupled to the central European Array for Gamma Levels Evaluations at the Heavy Ion Laboratory of the University of Warsaw. Internal conversion coefficients were obtained for transitions relevant to the decay of the isomeric states, allowing the determination of multipolarities and mixing ratios as well as hindrance factors. Two possible causes of the weakening of the $K$ forbiddenness, namely rotational $K$ mixing (Coriolis interaction) and triaxiality, are briefly discussed using schematic theoretical models.

We investigate the properties of ${}^7\mathrm{Li}$ with the JISP16 and chiral ${\mathrm{NNLO}}_{\mathrm{opt}}$ at next-to-next-to-leading order (NNLO) nucleon-nucleon interactions and ${}^7\mathrm{Be}$ with the JISP16 interaction in the ab initio no-core full configuration approach. We calculate selected observables that include energy spectra, point proton root-mean-square radii, electromagnetic moments, and transitions. We compare our results with experimental results, where available, as well as with results obtained using nucleon-nucleon plus three-nucleon interactions. We obtain reasonable agreement between theory and experiment for low-lying states that are dominated by $p$-shell configurations.

Background: A new mode of nuclear fission has been proposed by the FOBOS Collaboration, called collinear cluster tri-partition (CCT), and suggests that three heavy fission fragments can be emitted perfectly collinearly in low-energy fission. This claim is based on indirect observations via missing-energy events using the $2v2E$ method. This proposed CCT seems to be an extraordinary new aspect of nuclear fission. It is surprising that CCT escaped observation for so long given the relatively high reported yield of roughly $0.5\%$ relative to binary fission. These claims call for an independent verification with a different experimental technique.

Purpose: Verification experiments based on direct observation of CCT fragments with fission-fragment spectrometers require guidance with respect to the allowed kinetic-energy range, which we present in this paper. Furthermore, we discuss corresponding model calculations which, if CCT is found in such verification experiments, could indicate how the breakups proceed. Since CCT refers to collinear emission, we also study the intrinsic stability of collinearity.

Methods: Three different decay models are used that together span the timescales of three-body fission. These models are used to calculate the possible kinetic-energy ranges of CCT fragments by varying fragment mass splits, excitation energies, neutron multiplicities, and scission-point configurations. Calculations are presented for the systems ${}^{235}\mathrm{U}(n_{\text{th}},f)$ and ${}^{252}\mathrm{Cf}\left(sf\right)$, and the fission fragments previously reported for CCT; namely, isotopes of the elements Ni, Si, Ca, and Sn. In addition, we use semiclassical trajectory calculations with a Monte Carlo method to study the intrinsic stability of collinearity.

Results: CCT has a high net $Q$ value but, in a sequential decay, the intermediate steps are energetically and geometrically unfavorable or even forbidden. Moreover, perfect collinearity is extremely unstable, and broken by the slightest perturbation.

Conclusions: According to our results, the central fragment would be very difficult to detect due to its low kinetic energy, raising the question of why other $2v2E$ experiments could not detect a missing-mass signature corresponding to CCT. Considering the high kinetic energies of the outer fragments reported in our study, direct-observation experiments should be able to observe CCT. Furthermore, we find that a realization of CCT would require an unphysical fine tuning of the initial conditions. Finally, our stability calculations indicate that, due to the pronounced instability of the collinear configuration, a prolate scission configuration does not necessarily lead to collinear emission, nor does equatorial emission necessarily imply an oblate scission configuration. In conclusion, our results enable independent experimental verification and encourage further critical theoretical studies of CCT.

The study of the liquid gas phase transition in the fragmentation of nuclei in heavy ion collisions has been extended to the strangeness sector using the statistical model for multifragmentation. Helmholtz's free energy, specific heat, and a few other thermodynamic observables have been analyzed in order to examine the occurrence of phase transition in the strange matter. The bimodal behavior of the largest cluster formed in fragmentation also strongly indicates a coexistence of both the phases. The presence of hyperons strengthens the signals and also shifts the transition temperature to lower values.

Using the microscopic-macroscopic model based on the deformed Woods–Saxon single-particle potential and the Yukawa-plus-exponential macroscopic energy, we calculated static fission barriers $B_f$ for 1305 heavy and superheavy nuclei $98\le Z\le 126$, including even-even, odd-even, even-odd and odd-odd systems. For odd and odd-odd nuclei, adiabatic potential-energy surfaces were calculated by a minimization over configurations with one blocked neutron or/and proton on a level from the 10th below to the 10th above the Fermi level. The parameters of the model that have been fixed previously by a fit to masses of even-even heavy nuclei were kept unchanged. A search for saddle points has been performed by the “imaginary water flow” method on a basic five-dimensional deformation grid, including triaxiality. Two auxiliary grids were used for checking the effects of the mass asymmetry and hexadecapole nonaxiality. The ground states (g.s.) were found by energy minimization over configurations and deformations. We find that the nonaxiality significantly changes first and second fission saddle in many nuclei. The effect of the mass asymmetry, known to lower the second, very deformed saddles in actinides, in the heaviest nuclei appears at the less deformed saddles in more than 100 nuclei. It happens for those saddles in which the triaxiality does not play any role, which suggests a decoupling between effects of the mass asymmetry and triaxiality. We studied also the influence of the pairing interaction strength on the staggering of $B_f$ for odd- and even-particle numbers. Finally, we provide a comparison of our results with other theoretical fission barrier evaluations and with available experimental estimates.

In this paper, $\beta$-decay properties of even-even neutron-rich isotopes in the rare-earth mass region are studied within a microscopic theoretical approach based on a proton-neutron quasiparticle random-phase approximation. The underlying mean field is constructed self-consistently from a deformed Hartree-Fock calculation with Skyrme interactions and pairing correlations to which particle-hole and particle-particle residual interactions are added. Nuclei in this mass region participate in the astrophysical rapid neutron capture process and are directly involved in the generation of the rare-earth peak in the isotopic abundance pattern centered at $A\simeq 160$. The energy distributions of the Gamow-Teller strength as well as the $\beta$-decay half-lives and the $\beta$-delayed neutron-emission probabilities are discussed and compared with the available experimental information and with calculations based on different approaches.

We systematically study the tidal deformability for neutron and hyperon stars using relativistic mean field equations of state (EOSs). The tidal effect plays an important role during the early part of the evolution of compact binaries. Although, the deformability associated with the EOSs has a small correction, it gives a clean gravitational wave signature in binary inspiral. These are characterized by various Love numbers $k_l\left(l=2,3,4\right)$, that depend on the EOS of a star for a given mass and radius. The tidal effect of star could be efficiently measured through an advanced LIGO detector from the final stages of an inspiraling binary neutron star merger.

High-spin band structures of ${}^{200}\mathrm{Tl}$ have been studied by $\gamma$-ray spectroscopic methods using the ${}^{198}\mathrm{Pt}({}^7\mathrm{Li},5n){}^{200}\mathrm{Tl}$ reaction at 45 MeV of beam energy. The level scheme of ${}^{200}\mathrm{Tl}$ has been extended significantly and several new band structures have been established with the observation of 60 new transitions. The $\pi h_{9/2}\otimes \nu i_{13/2}$ oblate band has been extended beyond the particle alignment frequencies. The band structures and the other excited states have been compared with the neighboring odd-odd Tl isotopes. Total Routhian surface calculations have been performed to study the deformation and shape changes as a function of spin in this nucleus. These calculations could reproduce the particle alignment frequency and suggest that the neutron pair alignment in $\nu i_{13/2}$ orbital induces $\gamma$ softness in ${}^{200}\mathrm{Tl}$.

The $\alpha$ decay and proton radioactivity half-lives of some neutron-deficient nuclei are calculated using an effective liquid drop model (ELDM). It is found that the experimental half-lives of the two decay modes and the dominant decay mode can be well reproduced by the ELDM. Moreover, the predicted penetration probabilities ($P$) of proton radioactivity by the ELDM are in agreement with those by a microscopic model (MM). This allows us to make predictions on the competition of the two decay modes for nuclei whose experimental data are not available, which are useful for future measurements. In addition, the comparison between the predicted reduced proton radioactivity half-lives by the ELDM and the ones by a standard formula suggests that one is unlikely to observe large angular momentum transfers for nuclei with a very large Coulomb parameter $\chi$. Last, we find that in most isotope chains the proton radioactivity is the dominant decay mode for nuclei that are very close to the proton drip line. But with increasing neutron number $N$ the main decay mode is changed into $\alpha$ decay. With the decay energies the decay mode anomaly of ${}^{184}\mathrm{Bi}$ is discussed.

The charged pion multiplicity ratio in intermediate-energy heavy-ion collisions, a probe of the density dependence of symmetry energy above the saturation point, has been proven in a previous study to be extremely sensitive to the strength of the isovector $\mathrm{\Delta }\left(1232\right)$ potential in nuclear matter. As there is no knowledge, either from theory or experiment, about the magnitude of this quantity, the extraction of constraints on the slope of the symmetry energy at saturation by using exclusively the mentioned observable is hindered at present. It is shown that, by including the ratio of average $p_T$ of charged pions $\langle p_T^{\left({\pi }^{+}\right)}\rangle /\langle p_T^{\left({\pi }^{-}\right)}\rangle$ in the list of fitted observables, the noted problem can be circumvented. A realistic description of this observable requires accounting for the interaction of pions with the dense nuclear matter environment by the incorporation of the so-called $S$-wave and $P$-wave pion optical potentials. This is performed within the framework of a quantum molecular dynamics transport model that enforces the conservation of the total energy of the system. It is shown that constraints on the slope of the symmetry energy at saturation density and the strength of the $\mathrm{\Delta }$(1232) potential can be simultaneously extracted. A symmetry energy with a value of the slope parameter $L>50$ MeV is favored, at $1\sigma$ confidence level, from a comparison with published FOPI experimental data. A precise constraint will require experimental data more accurate than presently available, particularly for the charged pion multiplicity ratio, and better knowledge of the density and momentum dependence of the pion potential for the whole range of these two variables probed in intermediate-energy heavy-ion collisions.