Photon activation technique is used to obtain photofission mass distributions of ${}^{238}\mathrm{U}$ after irradiation in a bremsstrahlung beam with end-point energies 19.5, 29.1, 48.3, and 67.7 MeV. The weights of the symmetric (SL) and asymmetric (STI and STII) modes in the mass distributions of photofission of ${}^{238}\mathrm{U}$ and neutron-induced fission of ${}^{235,238}\text{U}$ at the average excitation energies of up to 20 MeV are calculated on the basis of the obtained results and other available data. The weight of the SL mode increases by about an order of magnitude as the average excitation energy increases from 8.5 to 17 MeV, while the weight of the STI mode decreases by two times, and the weight of the STII mode slightly increases. It is shown that the peak-to-valley ratios in photofission of ${}^{238}\mathrm{U}$ and neutron-induced fission of ${}^{235}\mathrm{U}$ are very close across almost the whole studied energy range. A similar conclusion is made concerning the behavior of asymmetric and symmetric fission modes in photofission of ${}^{238}\mathrm{U}$ and neutron-induced fission of ${}^{235}\mathrm{U}$ and ${}^{238}\mathrm{U}$.

A solvable extended Hamiltonian that includes multipair interactions among $s$ and $d$ bosons up to infinite order within the framework of the interacting boson model (IBM) is proposed to gain a better description of E(5) model results for finite-$N$ systems. Numerical fits to low-lying energy levels and reduced $E2$ transition rates within this extended version of the theory are presented for various $N$ values. The fits show that the extended Hamiltonian within the IBM provides a better description of the E(5) model results for small-$N$ cases, while the results of the model in the large-$N$ cases are close to those of the $\mathrm{E}\left(5\right)\text{−}{\beta }^{2n}$ type models studied previously.

I have used the relationship between computed energies in ${}^{10}\mathrm{He}$ and single-particle energies in ${}^9\mathrm{He}$ to provide limits on the $s_{1/2}$ energy. The absence of any bound states in ${}^{10}\mathrm{He}$ requires $E_{\mathrm{s}}>1\mathrm{MeV}$, contradicting all the experiments that have reported an $s$ state near threshold. The present analysis supports the view that the variation of ${}^{10}\mathrm{He}$ “ground-state” (g.s.) energies determined in various reactions is caused by the presence of two overlapping $0^{+}$ resonances. Results of the two simplest reactions—proton knockout and ($t,p$)—have been used to extract the g.s. and excited $0^{+}$ energies as a function of the mixing parameter $b^2$ between the $p$-shell and the ${\left(sd\right)}^2$ basis states.

The thermal properties of asymmetric nuclear matter are investigated in a relativistic mean-field approach. We start from free-space $NN$ interactions and derive in-medium self-energies by the Dirac-Brueckner theory. By the density-dependent relativistic hadron procedure we derive in a self-consistent approach density-dependent meson-baryon vertices. At the mean-field level, we include isoscalar and isovector-scalar and vector interactions. The nuclear equation of state is investigated for a large range of total baryon densities up to the neutron star regime, the full range of asymmetries $\xi =Z/A$ from symmetric nuclear matter to pure neutron matter, and temperatures up to $T\sim 100$ MeV. The isovector-scalar self-energies are found to modify strongly the thermal properties of asymmetric nuclear matter. A striking result is the change of phase transitions when isovector-scalar self-energies are included.

It is a well-established fact that intranuclear-cascade models generally overestimate the cross sections for one-proton removal from heavy, stable nuclei by a high-energy proton beam, but they yield reasonable predictions for one-neutron removal from the same nuclei and for one-nucleon removal from light targets. We use simple shell-model calculations to investigate the reasons for this deficiency. We find that a refined description of the neutron skin and of the energy density in the nuclear surface is crucial for the aforementioned observables, and that neither ingredient is sufficient if taken separately. As a by-product, the predictions for removal of several nucleons are also improved by the refined treatment.

With an effective Lagrangian approach, we analyze the $K^{-}p\to {\pi }^0{\Sigma }^0$ reaction to study the $\Lambda$ hyperon resonances by fitting the Crystal Ball data on differential cross sections and ${\Sigma }^0$ polarization with the center-of-mass energies of 1536–1676 MeV. Besides well-established Particle Data Group (PDG) four-star $\Lambda$ resonances around this energy range, the $\Lambda \left(1600\right){\frac{1}{2}}^{+}$ resonance, listed as a three-star resonance in the PDG data, is found to be definitely needed. In addition, there is strong evidence for the existence of a new $\Lambda \left({\frac{3}{2}}^{+}\right)$ resonance around 1680 MeV.

The nuclear reaction mechanism leading to the production of fragments with more neutrons than the projectile at intermediate energies is studied. A large enhancement in the production of these fragments is observed in the reactions with less neutron-rich projectiles or neutron-rich targets. This enhancement would be related to the difference of the neutron density at the nuclei surface as a factor influencing the process of nucleon exchange in peripheral collisions. From a practical viewpoint, such a nuclear reaction mechanism could provide a novel synthetic avenue to access extremely neutron-rich isotopes towards the neutron drip line.

We present a theoretical analysis of the competition between the so-called nuclear Jacobi and Poincaré shape transitions as a function of spin at high temperatures. The latter condition implies the method of choice, a realistic version of the nuclear liquid drop model, here the Lublin-Strasbourg drop model. We address specifically the fact that the Jacobi and Poincaré shape transitions are accompanied by the flattening of the total nuclear energy landscape as a function of the relevant deformation parameters, which enforces large-amplitude oscillation modes that need to be taken into account. For that purpose we introduce an approximate form of the collective Schrödinger equation whose solutions are used to calculate the most probable deformations associated with the nuclear Jacobi and Poincaré transitions. We discuss selected aspects of the new description focusing on the critical-spin values for both types of these transitions.

The level structure of the neutron-rich ${}^{69}\mathrm{Cu},{}^{71}\mathrm{Cu},$ and ${}^{73}\mathrm{Cu}$ isotopes has been investigated by means of multinucleon transfer reactions. The experiment was performed at Laboratori Nazionali di Legnaro using the AGATA Demonstrator array coupled to the PRISMA magnetic spectrometer. Lifetimes of excited states in Cu nuclei were measured with the recoil-distance Doppler-shift method. The resulting electromagnetic matrix elements for transitions from excited states in ${}^{69,71,73}\mathrm{Cu}$ nuclei are used to assess the collective or single-particle character of these states. The results are compared with predictions of large-scale shell-model calculations, giving further insight into the evolution of the proton $pf$ shell as neutrons fill the $1g_{9/2}$ orbital.

I investigate entanglement entropy of one-dimensional (1D) cluster states to discuss the delocalization of clusters in linear-chain $3\alpha$- and $4\alpha$-cluster states. In analysis of entanglement entropy of 1D Tohsaki-Horiuchi-Schuck-Röpke (THSR) and Brink-Bloch cluster wave functions, I show clear differences in the entanglement entropy between localized cluster wave functions and delocalized cluster wave functions. To clarify spatial regions where the entanglement entropy is generated by the delocalization of clusters, I analyze the spatial distribution of entanglement entropy. In the linear-chain $3\alpha$-cluster state, the delocalization occurs dominantly in a low-density tail region while it is relatively suppressed in an inner region because of the Pauli blocking effect between clusters. In the linear-chain $4\alpha$ state having a larger system size than the linear-chain $3\alpha$ state, the delocalization occurs in the whole system. The entanglement entropy is found to be a measure of the delocalization of clusters in the 1D cluster systems.

We introduce a method for isospin restoration in the calculation of nuclear matrix elements (NMEs) for $0\nu \beta \beta$ and $2\nu \beta \beta$ decay within the framework of the microscopic interacting boson model (IBM-2). With this method, we calculate the NMEs for all processes of interest in $0\nu {\beta }^{-}{\beta }^{-}$ and $2\nu {\beta }^{-}{\beta }^{-}$ and in $0\nu {\beta }^{+}{\beta }^{+}$, $0\nu \mathrm{EC}{\beta }^{+}$, $R0\nu \mathrm{ECEC}$, $2\nu {\beta }^{+}{\beta }^{+}$, $2\nu \mathrm{EC}{\beta }^{+}$, and $2\nu \mathrm{ECEC}$. With this method, the Fermi matrix elements for $2\nu \beta \beta$ vanish, and those for $0\nu \beta \beta$ are considerably reduced.

Spallation reactions on fissile nuclei represent an appropriate tool to investigate dissipative effects in nuclear fission. In this work, we have studied transient and dissipative effects in proton- and deuteron-induced fission on ${}^{208}\mathrm{Pb}$ at $500A$ MeV. A dedicated experimental setup optimized for inverse kinematics measurements made it possible to identify in atomic number both fission fragments with high resolution, and reconstruct the charge of the fissioning system. We could then determine the width of the fission fragments charge distribution as well as partial fission cross sections, both as a function of the charge of the fissioning system. These two complementary observables permitted us to investigate the dynamics of the process at small deformation, i.e., from the ground state to the saddle point. The description of these observables with advanced model calculations reveals the influence of the nuclear dissipation in the fission process at high excitation energy and in particular its manifestation through transient time effects.

We present here a comprehensive model to describe the bottomonium suppression data obtained from the CERN Large Hadron Collider (LHC) at a center-of-mass energy of $\sqrt{s_{NN}}=2.76$ TeV. We employ a quasiparticle model (QPM) equation of state for the quark-gluon plasma (QGP) expanding under Bjorken's scaling law. The current model includes the modification of the formation time based on the temperature of the QGP, color screening during bottomonium production, gluon-induced dissociation, and collisional damping due to the imaginary part of the potential between the $b\overline{b}$ pair. We propose a method for determining the temperature-dependent formation time of bottomonia using the solution of the time-independent Schrödinger equation and compare it with another approach based on time-dependent Schrödinger wave equation simulation. We find that these two independent methods based on different axioms give similar results for the formation time. Cold nuclear matter effects and feed-down from higher resonance states of ${\rm Y}$ have also been included in the present work. The suppression of the bottomonium states at midrapidity is determined as a function of centrality. The results compare closely with the recent centrality-dependent suppression data at the energies available at the CERN LHC in the midrapidity region.

We investigate the correlation between various aspects of the initial geometry of heavy ion collisions at the BNL Relativistic Heavy Ion Collider energies and the final anisotropic flow, using v-USPhydro, a $2+1$ event-by-event viscous relativistic hydrodynamical model. We test the extent of which shear and bulk viscosity affect the prediction of the final flow harmonics, $v_n$, from the initial eccentricities, ${\varepsilon }_n$. We investigate in detail the flow harmonics $v_1$ through $v_5$ where we find that $v_1,v_4$, and $v_5$ are dependent on more complicated aspects of the initial geometry that are especially important for the description of peripheral collisions, including a nonlinear dependence on eccentricities as well as a dependence on shorter-scale features of the initial density. Furthermore, we compare our results to previous results from NeXSPheRIO, a $3+1$ relativistic ideal hydrodynamical model that has a nonzero initial flow contribution, and find that the combined contribution from $3+1$ dynamics and nonzero, fluctuating initial flow decreases the predictive ability of the initial eccentricities, in particular for very peripheral collisions, but also disproportionately in central collisions.

In the present work, the properties of the light vector mesons ($\rho ,\omega$, and $\varphi$) in strange hadronic matter are studied using the QCD sum rule approach. The in-medium masses of the vector mesons are calculated from the modifications of the light quark condensates and the gluon condensates in the hadronic medium. The light quark condensates in the hadronic matter are obtained from the values of the nonstrange and strange scalar fields of the explicit chiral symmetry breaking term in a chiral SU(3) model. The in-medium gluon condensate is calculated through the medium modification of a scalar dilaton field, which is introduced into the chiral SU(3) model to simulate the scale symmetry breaking of QCD. The mass of the $\omega$ meson is observed to have initially a drop with increase in density and then a rise due to the scattering with the baryons. The mass of the $\rho$ meson is seen to drop with density due to decrease of the light quark condensates in the medium. The effects of isospin asymmetry and strangeness of the medium on the masses of the vector mesons are also studied in the present work. The $\varphi$ meson is observed to have marginal drop in its mass in the nuclear medium. However, the strangeness of the medium is seen to lead to an appreciable increase in its mass arising due to scattering with the hyperons.

We discuss the nuclear interactions of neutrinos versus those of antineutrinos, a relevant comparison for $\mathit{CP}$ violation experiments in the neutrino sector. We consider the MiniBooNE quasielastic-like double-differential neutrino and antineutrino cross sections that are dependent on the energy profiles of the neutrino fluxes and hence specific to the MiniBooNE setup. We combine them introducing their sum $(\nu +\overline{\nu })$ and their difference $(\nu -\overline{\nu })$. We show that the last combination gives general information on the multinucleon content of the axial-vector interference term. Our theoretical model reproduces well the two cross-section combinations, confirming the need for a sizable multinucleon component.

Based on an improved isospin- and momentum-dependent interaction, I have studied the qualitative effect of isospin splitting of nucleon effective mass on the specific shear viscosity of neutron-rich nuclear matter from a relaxation time approach. It is seen that for $m_n^{☆}>m_p^{☆}$, the relaxation time of neutrons is smaller, and the neutron flux between flow layers is weaker, leading to a smaller specific shear viscosity of neutron-rich matter compared to the case for $m_n^{☆}<m_p^{☆}$. The effect is larger in nuclear matter at higher densities, lower temperatures, and larger isospin asymmetries, but it does not affect the behavior of the specific shear viscosity much near nuclear liquid-gas phase transition.

Background: The impurity effect of hyperons on atomic nuclei has received a renewed interest in nuclear physics since the first experimental observation of appreciable reduction of $E2$ transition strength in low-lying states of the hypernucleus ${}_{\Lambda }^7\mathrm{Li}$. Many more data on low-lying states of $\Lambda$ hypernuclei will be measured soon for $sd$-shell nuclei, providing good opportunities to study the $\Lambda$ impurity effect on nuclear low-energy excitations.

Purpose: We carry out a quantitative analysis of the $\Lambda$ hyperon impurity effect on the low-lying states of $sd$-shell nuclei at the beyond-mean-field level based on a relativistic point-coupling energy density functional (EDF), considering that the $\Lambda$ hyperon is injected into the lowest positive-parity (${\Lambda }_s$) and negative-parity (${\Lambda }_p$) states.

Method: We adopt a triaxially deformed relativistic mean-field (RMF) approach for hypernuclei and calculate the $\Lambda$ binding energies of hypernuclei as well as the potential-energy surfaces (PESs) in the $(\beta ,\gamma )$ deformation plane. We also calculate the PESs for the $\Lambda$ hypernuclei with good quantum numbers by using a microscopic particle rotor model (PRM) with the same relativistic EDF. The triaxially deformed RMF approach is further applied in order to determine the parameters of a five-dimensional collective Hamiltonian (5DCH) for the collective excitations of triaxially deformed core nuclei. Taking ${}_{\Lambda }{}^{25,27}\mathrm{Mg}$ and ${}_{\Lambda }{}^{31}\mathrm{Si}$ as examples, we analyze the impurity effects of ${\Lambda }_s$ and ${\Lambda }_p$ on the low-lying states of the core nuclei.

Results: We show that ${\Lambda }_s$ increases the excitation energy of the $2_1^{+}$ state and decreases the $E2$ transition strength from this state to the ground state by $12\%\text{to}17\%$. On the other hand, ${\Lambda }_p$ tends to develop pronounced energy minima with larger deformation, although it modifies the collective parameters in such a way that the collectivity of the core nucleus can be either increased or decreased.

Conclusions: The quadrupole deformation significantly affects the $\Lambda$ binding energies of deformed hypernuclei. A beyond-mean-field approach with the dynamical correlations due to restoration of broken symmetries and shape fluctuation is essential in order to study the $\Lambda$ impurity effect in a quantitative way.

The excited states in the light nucleus ${}^9\mathrm{Be}$ are studied through $\beta$-delayed neutron decays from spin-polarized ${}^9{\mathrm{Li}}_{\mathrm{g}.\mathrm{s}.}$. The neutron transitions via ${}^5{\mathrm{He}}_{\mathrm{g}.\mathrm{s}.}$ from the 2.43-, 2.78-, 4.704-, 5.59-, and 7.94-MeV states in ${}^9\mathrm{Be}$ are observed for the first time, and the spins and parities ($I^{\pi }$'s) of the excited states in ${}^9\mathrm{Be}$ are assigned from $\beta \text{−}n$ coincidences and measurements of the $\beta$-decay asymmetries. The spin parity, $I^{\pi }$, of the 2.43-MeV state is assigned to be $5/2^{-}$, which is consistent with the reported value. The present results suggest that the $I^{\pi }$ values of the 2.78-, 4.704-, 5.59-, and 7.94-MeV states are $3/2^{-}$, $1/2^{-}$, $5/2^{-}$, and $3/2^{-}$, respectively, which are different from early reported values. However, shell-model calculations of the $p$ shell are in overall good agreement with the present results, except for the $I^{\pi }$ values of the 2.78- and 4.704-MeV states.

Using the evolutionary model-independent $S$-matrix approach, we show that a simultaneous correct description of the pictures of nuclear rainbow, prerainbow, and anomalous large-angle scattering (ALAS) in the ${}^4\mathrm{He}-{}^{40}\mathrm{Ca}$ elastic scattering can be achieved with help of the $S$-matrix moduli and the real nuclear phases exhibiting smooth monotonic dependencies on angular momentum, while the quantum deflection functions have a form characteristic of the nuclear rainbow case. The special role of the surface partial waves in the formation of ALAS is revealed.