Background: The quasiparticle random phase approximation (QRPA), within the framework of nuclear density functional theory (DFT), has been a standard tool to access the collective excitations of atomic nuclei. Recently, the finite amplitude method (FAM) was developed in order to perform the QRPA calculations efficiently without any truncation on the two-quasiparticle model space.

Purpose: We discuss the nuclear giant dipole resonance (GDR) in heavy rare-earth isotopes, for which the conventional matrix diagonalization of the QRPA is numerically demanding. A role of the Thomas-Reiche-Kuhn (TRK) sum rule enhancement factor, connected to the isovector effective mass, is also investigated.

Methods: The electric dipole photoabsorption cross section was calculated within a parallelized FAM-QRPA scheme. We employed the Skyrme energy density functional self-consistently in the DFT calculation for the ground states and FAM-QRPA calculation for the excitations.

Results: The mean GDR frequency and width are mostly reproduced with the FAM-QRPA, when compared to experimental data, although some deficiency is observed with isotopes heavier than erbium. A role of the TRK enhancement factor in actual GDR strength is clearly shown: its increment leads to a shift of the GDR strength to higher-energy region, without a significant change in the transition amplitudes.

Conclusions: The newly developed FAM-QRPA scheme shows remarkable efficiency, which enables one to perform systematic analysis of GDR for heavy rare-earth nuclei. The theoretical deficiency of the photoabsorption cross section could not be improved by only adjusting the TRK enhancement factor, suggesting the necessity of an approach beyond self-consistent QRPA and/or a more systematic optimization of the energy density functional (EDF) parameters.

We study the ground and excited resonance states of ${}^{26}\mathrm{O}$ with a three-body model of ${}^{24}\mathrm{O}+n+n$ taking into account the coupling to the continuum. To this end, we use the new experimental data for the invariant mass spectroscopy of the unbound ${}^{25}\mathrm{O}$ and ${}^{26}\mathrm{O}$ nuclei, and present an update of three-body model calculations for the two-neutron decay of the ${}^{26}\mathrm{O}$ nucleus. With the new model inputs determined with the ground-state decay of ${}^{26}\mathrm{O}$, we discuss the dineutron correlations and a halo nature of this nucleus, as well as the structure of the excited states. For the energy of the $2^{+}$ state, we achieve an excellent agreement with the experimental data with this calculation. We show that the $2^{+}$ state consists predominantly of the ${\left(d_{3/2}\right)}^2$ configuration, for which the pairing interaction between the valence neutrons slightly decreases its energy from the unperturbed one. We also discuss the structure of excited $0^{+}$ states of the ${}^{26}\mathrm{O}$ nucleus. In particular, we show the existence of an excited $0^{+}$ state at 3.38 MeV, which is mainly composed of the ${\left(f_{7/2}\right)}^2$ configuration.

The eigenfunctions of the two-rotors model are superpositions of states corresponding to precessions of the rotors around two orthogonal axes. In the application of the model to a system of particles, such a structure becomes a coherent entanglement of many particles. In nuclear physics such an entanglement has not been directly confirmed. I show that it is possible to come to a definite conclusion about its existence by measuring the electromagnetic transition probabilities for the $J=3$ member of the scissors-mode rotational band and for higher excited states with intrinsic energy twice that of the scissors mode. The present results are relevant to single-domain magnetic nanoparticles.

Using the Polyakov–Nambu–Jona-Lasinio model, we study the spinodal instability of a baryon-rich quark-gluon plasma in the linear response theory. We find that the spinodal unstable region in the temperature and density plane shrinks with increasing wave number of the unstable mode and is also reduced if the effect of the Polyakov loop is not included. In the small wave number or long wavelength limit, the spinodal boundaries in both cases of with and without the Polyakov loop coincide with those determined from the isothermal spinodal instability in the thermodynamic approach. Also, the vector interactions among quarks are found to suppress unstable modes of all wave numbers. Moreover, the growth rate of unstable modes initially increases with the wave number but is reduced when the wave number becomes large. Including the collisional effect from quark scattering via the linearized Boltzmann equation, we further find that it decreases the growth rate of unstable modes of all wave numbers. The relevance of these results to relativistic heavy ion collisions is discussed.

We perform a calculation of the cross section for nine reactions induced by $\overline{K}$ scattering on protons. The reactions studied are $K^{-}p\to \mathrm{\Lambda }{\pi }^{+}{\pi }^{-}$, $K^{-}p\to {\mathrm{\Sigma }}^0{\pi }^{+}{\pi }^{-}$, $K^{-}p\to \mathrm{\Lambda }{\pi }^0\eta$, $K^{-}p\to {\mathrm{\Sigma }}^0{\pi }^0\eta$, $K^{-}p\to {\mathrm{\Sigma }}^{+}{\pi }^{-}\eta$, ${\overline{K}}^{0}p\to \mathrm{\Lambda }{\pi }^{+}\eta$, ${\overline{K}}^{0}p\to {\mathrm{\Sigma }}^0{\pi }^{+}\eta$, ${\overline{K}}^{0}p\to {\mathrm{\Sigma }}^{+}{\pi }^{+}{\pi }^{-}$, and ${\overline{K}}^{0}p\to {\mathrm{\Sigma }}^{+}{\pi }^0\eta$. We find that in the reactions producing ${\pi }^{+}{\pi }^{-}$, a clear peak for the $f_0\left(980\right)$ resonance is found, while no trace of $f_0\left(500\right)$ appears. Similarly, in the cases of $\pi \eta$ production, a strong peak is found for the $a_0\left(980\right)$ resonance, with the characteristic strong cusp shape. Cross sections and invariant mass distributions are evaluated which should serve, by comparing them with future data, to test the dynamics of the chiral unitary approach used for the evaluations and the nature of these resonances.

There is significant evidence supporting the existence of deformed ground states within the neutron-rich $N\approx 20$ neon, sodium, and magnesium isotopes that make up what is commonly called the “island of inversion.” However, the rotational band structures, which are a characteristic fingerprint of a rigid nonspherical shape, have yet to be observed. In this work, we report on a measurement and analysis of the yrast (lowest lying) rotational band in ${}^{32}\mathrm{Mg}$ up to spin $I=6^{+}$ produced in a two-step projectile fragmentation reaction and observed using the state-of-the-art $\gamma$-ray tracking detector array, GRETINA ($\gamma$-ray energy tracking in-beam nuclear array). Large-scale shell-model calculations using the SDPF-U-MIX effective interaction show excellent agreement with the new data. Moreover, a theoretical analysis of the spectrum of rotational states as a function of the pairing gap, together with cranked-shell-model calculations, provides intriguing evidence for a reduction in pairing correlations with increased angular momentum, also in line with the shell-model results.

A new neutron-cooling mechanism is proposed with potential benefits for novel intense sources of very cold neutrons with wavelengths $>2$ nm, and for enhancing the production of ultracold neutrons. It employs inelastic magnetic scattering in weakly absorbing, cold paramagnetic systems. Kinetic energy is removed from the neutron stepwise in constant decrements determined by the Zeeman energy of paramagnetic atoms or ions in an external magnetic field, or by zero-field level splittings in magnetic molecules. The stationary neutron transport equation is analyzed for an infinite, homogeneous medium with Maxwellian neutron sources, using inelastic scattering cross sections derived in an appendix. Nonmagnetic inelastic scattering processes are neglected. The solution therefore still underestimates very cold neutron densities that should be achievable in a real medium. Molecular oxygen with its triplet ground state appears particularly promising, notably as a host in fully deuterated ${\mathrm{O}}_2$-clathrate hydrate. Other possibilities are dry ${\mathrm{O}}_2\text{−}{}^4\mathrm{He}$ van der Waals clusters and ${\mathrm{O}}_2$ intercalated in fcc-${\mathrm{C}}_{60}$. For conversion of cold to ultracold neutrons, where an incident neutron imparts only a single energy quantum to the medium, the paramagnetic scattering in the clathrate system is found to be stronger, by more than an order of magnitude, than the single-phonon emission in superfluid helium, when evaluated for an incident neutron spectrum with the optimum temperature for the respective medium. Moreover, the multistep paramagnetic cooling cascade leads to further strong enhancements of very cold neutron densities, e.g., by a factor 14 (57) for an initial neutron temperature of $30\mathrm{K} \left(100\mathrm{K}\right)$, for the moderator held at about $1.3\mathrm{K}$. Due to a favorable Bragg cutoff of the ${\mathrm{O}}_2$ clathrate, the cascade-cooling can take effect in a moderator with linear extensions smaller than a meter.

A consistent Hartree-Fock study of the equation of state (EOS) of asymmetric nuclear matter at finite temperature has been performed using realistic choices of the effective, density-dependent nucleon-nucleon $\left(\mathit{NN}\right)$ interaction, which were successfully used in different nuclear structure and reaction studies. Given the importance of the nuclear symmetry energy in the neutron star formation, EOSs associated with different behaviors of the symmetry energy were used to study hot asymmetric nuclear matter. The slope of the symmetry energy and nucleon effective mass with increasing baryon density was found to affect the thermal properties of nuclear matter significantly. Different density-dependent $\mathit{NN}$ interactions were further used to study the EOS of hot protoneutron star (PNS) matter of the $npe\mu \nu$ composition in $\beta$ equilibrium. The hydrostatic configurations of PNS in terms of the maximal gravitational mass $M_{\max }$ and radius, central density, pressure, and temperature at the total entropy per baryon $S/A=1,2$, and 4 have been determined in both the neutrino-free and neutrino-trapped scenarios. The obtained results show consistently a strong impact of the symmetry energy and nucleon effective mass on thermal properties and composition of hot PNS matter. $M_{\max }$ values obtained for the (neutrino-free) $\beta$-stable PNS at $S/A=4$ were used to assess time $t_{\mathrm{BH}}$ of the collapse of a $40M_{\odot }$ protoneutron progenitor to a black hole, based on a correlation between $t_{\mathrm{BH}}$ and $M_{\max }$ found from the hydrodynamic simulation by Hempel et al. [Astrophys. J. 748, 70 (2012)].

There has been a great deal of attention given to the low-lying energy spectrum in a nucleus because of the abundance of experimental data. Likewise, perhaps to a lesser extent but still significant, the high end for a given configuration has been examined. Here, using single $j$ shell calculations as a guide, we examine the middle part of the spectrum resulting from single $j$ shell calculations. Seniority arguments are used to partially explain the midshell behaviors even though in general seniority is not a good quantum number for mixed systems of neutrons and protons.

Low-lying excited states in ${}^{72}\mathrm{Ni}$ have been investigated in an in-flight fission experiment at the RIBF facility of the RIKEN Nishina Center. The combination of the state-of-the-art BigRIPS and EURICA setups has allowed for a very accurate study of the $\beta$ decay from ${}^{72}\mathrm{Co}$ to ${}^{72}\mathrm{Ni}$, and has provided first experimental information on the decay sequence ${}^{72}\mathrm{Fe}\to {}^{72}\mathrm{Co}\to {}^{72}\mathrm{Ni}$ and on the delayed neutron-emission branch ${}^{73}\mathrm{Co}\to {}^{72}\mathrm{Ni}$. Accordingly, we report nearly 60 previously unobserved $\gamma$ transitions which deexcite 21 new levels in ${}^{72}\mathrm{Ni}$. Evidence for the location of the so-sought-after $\left(4_2^{+}\right),\left(6_2^{+}\right)$, and $\left(8_1^{+}\right)$ seniority states is provided. As well, the existence of a low-spin $\beta$-decaying isomer in odd-odd neutron-rich Co isotopes is confirmed for mass $A=72$. The new experimental information is compared to simple shell-model calculations including only neutron excitations across the $fpg$ shells. It is shown that, in general, the calculations reproduce well the observed states.

Background: Elastic scattering is probably the main event in the interactions of nucleons with nuclei. Even if this process has been extensively studied over the last years, a consistent description, i.e., starting from microscopic two- and many-body forces connected by the same symmetries and principles, is still under development.

Purpose: In this work we study the domain of applicability of microscopic two-body chiral potentials in the construction of an optical potential.

Methods: We basically follow the Kerman, McManus, and Thaler approach [Ann. Phys. (NY) 8, 551 (1959)] to build a microscopic complex optical potential, and then we perform some test calculations on ${}^{16}\mathrm{O}$ at different energies.

Results:. Our conclusion is that a particular set of potentials with a Lippmann–Schwinger cutoff at relatively high energies (above 500 MeV) reproduces best the scattering observables.

Conclusions: Our work shows that building an optical potential within chiral perturbation theory is a promising approach for describing elastic proton scattering; in particular, in view of the future inclusion of many-body forces that naturally arises in such a framework.

We make predictions for momentum-integrated elliptic and triangular flow as well as mean transverse momentum for 5.02 TeV Pb-Pb collisions, as planned at the CERN Large Hadron Collider. We use hydrodynamic calculations to predict the change of these observables as the center-of-mass collision energy evolves from 2.76 TeV to 5.02 TeV per nucleon pair. By using previously measured values as a baseline, we are able to make a robust prediction without relying on a particular model for initial conditions and without precise knowledge of medium properties such as viscosity. Thus, though the predicted changes are small, they can provide a significant test of the current hydrodynamic picture of heavy-ion collisions.

We present a formulation of the compositeness for baryonic resonances to discuss the meson-baryon molecular structure inside the resonances. For this purpose, we derive a relation between the residue of the scattering amplitude at the resonance pole position and the two-body wave function of the resonance in a sophisticated way, and we define the compositeness as the norm of the two-body wave functions. As applications, we investigate the compositeness of the $\mathrm{\Delta }\left(1232\right),N\left(1535\right)$, and $N\left(1650\right)$ resonances from precise $\pi N$ scattering amplitudes in a unitarized chiral framework with the interaction up to the next-to-leading order in chiral perturbation theory. The $\pi N$ compositeness for the $\mathrm{\Delta }\left(1232\right)$ resonance is evaluated in the $\pi N$ single-channel scattering, and we find that the $\pi N$ component inside $\mathrm{\Delta }\left(1232\right)$ in the present framework is non-negligible, which supports the previous work. On the other hand, the compositeness for the $N\left(1535\right)$ and $N\left(1650\right)$ resonances is evaluated in a coupled-channel approach, resulting that the $\pi N,\eta N,K\mathrm{\Lambda }$, and $K\mathrm{\Sigma }$ components are negligible for these resonances.

We present the mass excesses of ${}^{59\text{–}64}\mathrm{Cr}$, obtained from recent time-of-flight nuclear mass measurements at the National Superconducting Cyclotron Laboratory at Michigan State University. The mass of ${}^{64}\mathrm{Cr}$ is determined for the first time, with an atomic mass excess of $-33.48\left(44\right)$ MeV. We find a significantly different two-neutron separation energy $S_{2n}$ trend for neutron-rich isotopes of chromium, removing the previously observed enhancement in binding at $N=38$. Additionally, we extend the $S_{2n}$ trend for chromium to $N=40$, revealing behavior consistent with the previously identified island of inversion in this region. We compare our results to state-of-the-art shell-model calculations performed with a modified Lenzi-Nowacki-Poves-Sieja interaction in the $fp$ shell, including the $g_{9/2}$ and $d_{5/2}$ orbits for the neutron valence space. We employ our result for the mass of ${}^{64}\mathrm{Cr}$ in accreted neutron star crust network calculations and find a reduction in the strength and depth of electron-capture heating from the $A=64$ isobaric chain, resulting in a cooler than expected accreted neutron star crust. This reduced heating is found to be due to the $>1$-MeV reduction in binding for ${}^{64}\mathrm{Cr}$ with respect to values from commonly used global mass models.

We have used realistic local interactions based on the recent update of the strangeness $-2$ Nijmegen ESC08c potential to calculate the bound-state problem of the $\mathrm{\Xi }NN$ system in the $\left(I\right)J^P=\left(\frac{1}{2}\right){\frac{3}{2}}^{+}$ state. We found that this system presents a deeply bound state lying $13.5$ MeV below the $\mathrm{\Xi }d$ threshold. Since in the lowest order, pure $S$-wave configuration, this system cannot decay into the open $\mathrm{\Lambda }\mathrm{\Lambda }N$ channel, its decay width is expected to be very small. We have also recalculated the $\left(I\right)J^P=\left(\frac{3}{2}\right){\frac{1}{2}}^{+}$ state and we have compared our results with those of quark-model-based potentials.

High-spin states in ${}^{132}\mathrm{Te}$, an isotope with two proton particles and two neutron holes outside of the ${}^{132}\mathrm{Sn}$ doubly magic core, have been extended up to an excitation energy of 6.17 MeV. The prompt-delayed coincidence technique has been used to correlate states above the $T_{1/2}=3.70\left(9\right)\mu \text{s}$ isomer in ${}^{132}\mathrm{Te}$ to the lower states using ${}^{232}\mathrm{Th}({}^7\mathrm{Li},f)$ at 5.4 MeV/u and the Indian National Gamma Array (INGA). With ${}^9\mathrm{Be}({}^{238}\mathrm{U},f)$ at 6.2 MeV/u and EXOGAM $\gamma$-array coupled with the VAMOS++ spectrometer, the level scheme was extended to higher excitation energies. The high-spin positive-parity states, above $J^{\pi }={10}^{+}$, in ${}^{132}\mathrm{Te}$ are expected to arise from the alignment of the particles in the high-$j$ orbitals lying close to the Fermi surface, the $\pi g_{7/2}^2$, and the $\nu h_{11/2}^{-2}$ configurations. The experimental level scheme has been compared with the large scale shell model calculations. A reduction in the $p\text{−}n$ interaction strength resulted in an improved agreement with the measurements up to the spin of $15\hslash$. In contrast, the comparison of the differences between the experiment and these calculations for the $N=76,78$ isotones of Te and Sn shows the increasing disagreement as a function of spin, where the magnitude is larger in Te than in Sn. This behavior could possibly be attributed to the deficiencies in the $p\text{−}n$ correlations, in addition to the $n\text{−}n$ correlations in Sn.

I have estimated the energies of several unbound states of ${}^{12}\mathrm{Be}$ and their spectroscopic factors for decay to the $1/2^{+}$ ground state and $1/2^{-}$ first-excited state of ${}^{11}\mathrm{Be}$. These are then used to estimate the expected widths for such decays. Results for likely $3^{-}$ and $4^{+}$ states are good. I find that only $0^{+}$ and/or $2^{+}$ states can account for the width recently observed for a state decaying with a centroid neutron energy of 1.24 MeV.

The ${}^{138}\mathrm{Te}$ and ${}^{140}\mathrm{Xe}$ nuclei have been reinvestigated using prompt $\gamma$-ray data from spontaneous fission of ${}^{248}\mathrm{Cm}$, collected with the EUROGAM2 Ge array. $\gamma$ bands have been identified in both nuclei. The $\gamma$ band observed in ${}^{138}\mathrm{Te}$, a nucleus with only six valence nucleons, indicates the presence of collectivity very close to the doubly magic ${}^{132}\mathrm{Sn}$ core. Such band is even more pronounced in ${}^{140}\mathrm{Xe}$, the $N$ = 86 isotone of ${}^{138}\mathrm{Te}$. The newly observed bands are interpreted within the shell model, which reproduce well the $\gamma$ collectivity at $N$ = 86.

A microscopic version of the continuum discretized coupled channel (CDCC) method is used to investigate ${}^6\mathrm{He}$ scattering on ${}^{27}\mathrm{Al},{}^{58}\mathrm{Ni},{}^{120}\mathrm{Sn}$, and ${}^{208}\mathrm{Pb}$ at energies around the Coulomb barrier. The ${}^6\mathrm{He}$ nucleus is described by an antisymmetric 6-nucleon wave function, defined in the resonating group method. The ${}^6\mathrm{He}$ continuum is simulated by square-integrable positive-energy states. The model is based only on well-known nucleon-target potentials and therefore does not depend on any adjustable parameter. I show that experimental elastic cross sections are fairly well reproduced. The calculation suggests that breakup effects increase for high-mass targets. For a light system such as ${}^6\mathrm{He}+{}^{27}\mathrm{Al}$, breakup effects are small, and a single-channel approximation provides fair results. This property is explained by a very simple model, based on the sharp cutoff approximation for the scattering matrix. I also investigate the ${}^6\mathrm{He}$-target optical potentials, which confirm that breakup channels are more important when the mass increases. At large distances, polarization effects increase the Coulomb barrier and provide a long-tail absorption component in the imaginary part of the nucleus-nucleus interaction.

A study of fusion-evaporation and (partly) fusion-fission channels for the ${}^{88}\mathrm{Mo}$ compound nucleus, produced at different excitation energies in the reaction ${}^{48}\mathrm{Ti}+{}^{40}\mathrm{Ca}$ at 300, 450, and 600 MeV beam energies, is presented. Fusion-evaporation and fusion-fission cross sections have been extracted and compared with the existing systematics. Experimental data concerning light charged particles have been compared with the prediction of the statistical model in its implementation in the gemini++ code, well suited even for high spin systems, in order to tune the main model parameters in a mass region not abundantly covered by exclusive experimental data. Multiplicities for light charged particles emitted in fusion evaporation events are also presented. Some discrepancies with respect to the prediction of the statistical model have been found for forward emitted $\alpha$ particles; they may be due both to pre-equilibrium emission and to reaction channels (such as deep inelastic collisions or quasifission/quasifusion) different from the compound nucleus formation.