The structure and decay dynamics for $0^{+}$ and $2^{+}$ continuum excitations of ${}^{26}\mathrm{O}$ are investigated in a three-body ${}^{24}\mathrm{O}+n+n$ model. The validity of a simple approximation for the cross section profile for long-lived $2n$ emission is demonstrated. A sequence of three $0^{+}$ monopole (“breathing mode” type) excited states is predicted. These states could probably be interpreted as analogs of Efimov states pushed in the continuum due to insufficient binding. The calculated energies of the $2^{+}$ states are related to the excitation spectrum of ${}^{25}\mathrm{O}$. We discuss the correlation between the predicted ${}^{26}\mathrm{O}$ spectrum and experimental observations.

We apply the three-flavor (Polyakov-)Nambu-Jona-Lasinio model to generate baryons as quark-diquark bound states using many-body techniques at finite temperature. All the baryonic states belonging to the octet and decuplet flavor representations are generated in the isospin-symmetric case. For each state we extract the melting temperature at which the baryon may decay into a quark-diquark pair. We seek for an evidence of the strangeness dependence of the baryon melting temperature as suggested by the statistical thermal models and supported by lattice quantum chromodynamics results. A clear and robust signal for this claim is found, pointing to a flavor dependence of the hadronic deconfinement temperature.

We report on new measurements of the beam asymmetry for $\omega$ photoproduction on protons and neutrons in hydrogen and deuterium targets from the GRAAL Collaboration. The beam asymmetry values are extracted from the reaction threshold ($E_{\gamma }=1.1$ GeV in the free nucleon kinematics) up to 1.5 GeV of incoming photon energy. For the first time both the radiative and the three-pion decay channels are simultaneously investigated on the free proton. Results from the two decay channels are in agreement, leading to the world's most precise measurements of the beam asymmetry for $\omega$ photoproduction off free protons. First experimental results on the deuteron allow the extraction of the $\mathrm{\Sigma }$ beam asymmetry on quasifree nucleons. The beam asymmetry angular distributions obtained for the free and the quasifree kinematics show the same behavior, similar to the findings in pseudoscalar meson photoproduction reactions. First results of the beam asymmetry on the quasifree neutrons are presented, showing different strengths and angular distributions from the results on the proton target.

The $\overline{K}+N\to K+\mathrm{\Xi }$ reaction is studied for center-of-momentum energies ranging from threshold to 3 GeV in an effective Lagrangian approach that includes the hyperon $s$- and $u$-channel contributions as well as a phenomenological contact amplitude. The latter accounts for the rescattering term in the scattering equation and possible short-range dynamics not included explicitly in the model. Existing data are well reproduced and three above-the-threshold resonances were found to be required to describe the data, namely, the $\mathrm{\Lambda }\left(1890\right), \mathrm{\Sigma }\left(2030\right)$, and $\mathrm{\Sigma }\left(2250\right)$. For the latter resonance we have assumed the spin-parity of $J^P=5/2^{-}$ and a mass of 2265 MeV. The $\mathrm{\Sigma }\left(2030\right)$ resonance is crucial in achieving a good reproduction of not only the measured total and differential cross sections but also the recoil polarization asymmetry. More precise data are required before a more definitive statement can be made about the other two resonances, in particular, about the $\mathrm{\Sigma }\left(2250\right)$ resonance that is introduced to describe a small bump structure observed in the total cross section of $K^{-}+p\to K^{+}+{\mathrm{\Xi }}^{-}$. The present analysis also reveals a peculiar behavior of the total cross-section data in the threshold energy region in $K^{-}+p\to K^{+}+{\mathrm{\Xi }}^{-}$, where the $P$ and $D$ waves dominate instead of the usual $S$ wave. Predictions for the target-recoil asymmetries of the $\overline{K}+N\to K+\mathrm{\Xi }$ reaction are also presented.

The strongly coupled phase of the quark-gluon plasma (QGP) is studied here by resorting to a $T$-matrix formulation in which the medium is seen as a nonideal gas of quasiparticles (quarks, antiquarks, and gluons) interacting nonpertubatively. In the temperature range under study, (1–5)$T_c$, where $T_c$ is the temperature of deconfinement, the interactions are expected to be strong enough to generate bound states. The dissociation temperature of such binary bound states is thus computed here. The more the quasiparticles involved in the binary system are heavy, the more the bound state is likely to survive significantly above $T_c$. Then the QGP equations of state at zero and small baryonic potential are computed for $N_f=2$ and $N_f=2+1$ by resorting to the Dashen, Ma, and Bernstein formulation of statistical mechanics. Comparisons with current lattice QCD data are presented.

The anisotropies in the pressure obtained from the energy-momentum tensor are studied for magnetized quark matter within the su(3) Nambu-Jona-Lasinio model for both $\beta$-equilibrium matter and quark matter with equal quark chemical potentials. The effect of the magnetic field on the particle polarization, magnetization, and quark matter constituents is discussed. It is shown that the onset of the $s$ quark after chiral symmetry restoration of the $u$ and $d$ quarks gives rise to a special effect on the magnetization in the corresponding density range: A quite small magnetization just before the $s$ onset is followed by a strong increase of this quantity as soon as the $s$ quark sets in. It is also demonstrated that for $B<{10}^{18}$ G within the two scenarios discussed, always considering a constant magnetic field, the two components of pressure are practically coincident.

The lifetime of the $2^{+}\to 0_{\mathrm{g}.\mathrm{s}.}^{+}$ transition in the neutron-deficicient nucleus ${}^{112}\mathrm{Te}$ has been measured for the first time using the DPUNS plunger and the recoil distance Doppler shift technique. The deduced value for the reduced transition probability is $B(E2:0_{\mathrm{g}.\mathrm{s}.}^{+}\to 2^{+})=0.46\pm 0.04e^2{\mathrm{b}}^2$, indicating that there is no unexpected enhancement of the $B(E2:0_{\mathrm{g}.\mathrm{s}.}^{+}\to 2^{+})$ values in Te isotopes below the midshell. The result is compared to and discussed in the framework of large-scale shell-model calculations.

The van der Waals (VDW) equation of state is a simple and popular model to describe the pressure function in equilibrium systems of particles with both repulsive and attractive interactions. This equation predicts the existence of a first-order liquid-gas phase transition and contains a critical point. Two steps to extend the VDW equation and make it appropriate for new physical applications are carried out in this paper: (i) the grand canonical ensemble formulation and (ii) the inclusion of the quantum statistics. The VDW equation with Fermi statistics is then applied to a description of the system of interacting nucleons. The VDW parameters $a$ and $b$ are fixed to reproduce the properties of nuclear matter at saturation density $n_0=0.16{\mathrm{fm}}^{-3}$ and zero temperature. The model predicts a location of the critical point for the symmetric nuclear matter at temperature $T_c\cong 19.7$ MeV and nucleon number density $n_c\cong 0.07{\mathrm{fm}}^{-3}$.

The one-neutron knock-out reaction ${}^1\mathrm{H}({}^{20}\mathrm{C},{}^{19}\mathrm{C}\gamma )$ was studied at RIKEN using the DALI2 array. A $\gamma$-ray transition was observed at 198(10) keV. Based on the comparison between the experimental production cross section and theoretical predictions, the transition was assigned to the de-excitation of the $3/2_1^{+}$ state to the ground state.

The spectroscopy of ${}^{76}\mathrm{Se}$ has been studied using the ${}^{70}\mathrm{Zn}({}^{12}\mathrm{C}, \alpha 2{\mathrm{n})}^{76}\mathrm{Se}$ fusion evaporation reaction. The yrast band of ${}^{76}\mathrm{Se}$ has been extended to substantially higher spin, allowing observation of the second band crossing. The much-delayed $g_{9/2}$ proton-pair alignment is discussed in terms of the cranked shell model and most likely is caused by a shape transition from prolate to oblate along the yrast line occurring in ${}^{76}\mathrm{Se}$. Based on the systematic investigation of the band crossings associated with the $g_{9/2}$ quasiparticle alignments and their relationships with the shape evolutions in the even-$A$ Se and Kr isotopes, a comprehensive picture of shape evolution along with spin and isospin in these nuclei is obtained.

Background: Shape coexistence in heavy nuclei poses a strong challenge to state-of-the-art nuclear models, where several competing shape minima are found close to the ground state. A classic region for investigating this phenomenon is in the region around $Z=82$ and the neutron midshell at $N=104$.

Purpose: Evidence for shape coexistence has been inferred from $\alpha$-decay measurements, laser spectroscopy, and in-beam measurements. While the latter allow the pattern of excited states and rotational band structures to be mapped out, a detailed understanding of shape coexistence can only come from measurements of electromagnetic matrix elements.

Method: Secondary, radioactive ion beams of ${}^{202}\mathrm{Rn}$ and ${}^{204}\mathrm{Rn}$ were studied by means of low-energy Coulomb excitation at the REX-ISOLDE in CERN.

Results: The electric-quadrupole ($E2$) matrix element connecting the ground state and first excited $2_1^{+}$ state was extracted for both ${}^{202}\mathrm{Rn}$ and ${}^{204}\mathrm{Rn}$, corresponding to $B(E2;2_1^{+}\to 0_1^{+})={29}_{-8}^{+8}$ and ${43}_{-12}^{+17}$ W.u., respectively. Additionally, $E2$ matrix elements connecting the $2_1^{+}$ state with the $4_1^{+}$ and $2_2^{+}$ states were determined in ${}^{202}\mathrm{Rn}$. No excited $0^{+}$ states were observed in the current data set, possibly owing to a limited population of second-order processes at the currently available beam energies.

Conclusions: The results are discussed in terms of collectivity and the deformation of both nuclei studied is deduced to be weak, as expected from the low-lying level-energy schemes. Comparisons are also made to state-of-the-art beyond-mean-field model calculations and the magnitude of the transitional quadrupole moments are well reproduced.

The yields of over 200 projectile-like fragments (PLFs) and target-like fragments (TLFs) from the interaction of ($E_{\mathrm{c}.\mathrm{m}.}=450$ MeV) ${}^{136}\text{Xe}$ with a thick target of ${}^{208}\text{Pb}$ were measured using Gammasphere and off-line $\gamma$-ray spectroscopy, giving a comprehensive picture of the production cross sections in this reaction. The measured yields were compared to predictions of the grazing model and the predictions of Zagrebaev and Greiner using a quantitative metric, the theory evaluation factor $\mathit{t}ef$. The grazing model predictions are adequate for describing the yields of nuclei near the target or projectile but they grossly underestimate the yields of all other products. The predictions of Zagrebaev and Greiner correctly describe the magnitude and maxima of the observed TLF transfer cross sections for a wide range of transfers ($\mathrm{\Delta }Z=-8$ to $\mathrm{\Delta }Z=+2$). However, for $\mathrm{\Delta }Z=+4$, the observed position of the maximum in the distribution is four neutrons richer than the predicted maximum. The predicted yields of the neutron-rich $N=126$ nuclei exceed the measured values by two orders of magnitude. Correlations between TLF and PLF yields are discussed.

Background: Exotic nonspherical nuclear pasta shapes are expected in nuclear matter at just below saturation density because of competition between short-range nuclear attraction and long-range Coulomb repulsion.

Purpose: We explore the impact nuclear pasta may have on nucleosynthesis during neutron star mergers when cold dense nuclear matter is ejected and decompressed.

Methods: We use a hybrid CPU/GPU molecular dynamics (MD) code to perform decompression simulations of cold dense matter with 51 200 and 409 600 nucleons from $0.080{\mathrm{fm}}^{-3}$ down to $0.00125{\mathrm{fm}}^{-3}$. Simulations are run for proton fractions $Y_P=$ 0.05, 0.10, 0.20, 0.30, and 0.40 at temperatures $T=$ 0.5, 0.75, and 1.0 MeV. The final composition of each simulation is obtained using a cluster algorithm and compared to a constant density run.

Results: Size of nuclei in the final state of decompression runs are in good agreement with nuclear statistical equilibrium (NSE) models for temperatures of $1\mathrm{MeV}$ while constant density runs produce nuclei smaller than the ones obtained with NSE. Our MD simulations produces unphysical results with large rod-like nuclei in the final state of $T=0.5\mathrm{MeV}$ runs.

Conclusions: Our MD model is valid at higher densities than simple nuclear statistical equilibrium models and may help determine the initial temperatures and proton fractions of matter ejected in mergers.

The two-neutrino double-$\beta$ Gamow-Teller and Fermi transitions are studied within an exactly solvable model, which allows a violation of both spin-isospin SU(4) and isospin SU(2) symmetries, and is expressed with generators of the SO(8) group. It is found that this model reproduces the main features of realistic calculation within the quasiparticle random-phase approximation with isospin symmetry restoration concerning the dependence of the two-neutrino double-$\beta$ decay matrix elements on isovector and isoscalar particle-particle interactions. By using perturbation theory an explicit dependence of the two-neutrino double-$\beta$ decay matrix elements on the like-nucleon pairing, particle-particle $T=0$ and $T=1$, and particle-hole proton-neutron interactions is obtained. It is found that double-$\beta$ decay matrix elements do not depend on the mean field part of Hamiltonian and that they are governed by a weak violation of both SU(2) and SU(4) symmetries by the particle-particle interaction of Hamiltonian. It is pointed out that there is a dominance of two-neutrino double-$\beta$ decay transition through a single state of intermediate nucleus. The energy position of this state relative to energies of initial and final ground states is given by a combination of strengths of residual interactions. Further, energy-weighted Fermi and Gamow-Teller sum rules connecting $\mathrm{\Delta }Z=2$ nuclei are discussed. It is proposed that these sum rules can be used to study the residual interactions of the nuclear Hamiltonian, which are relevant for charge-changing nuclear transitions.

Nuclear scissors modes are considered in the frame of the Wigner-function moments method generalized to take into account spin degrees of freedom and pair correlations simultaneously. A new source of nuclear magnetism, connected with counter rotation of spins up and down around the symmetry axis (hidden angular momenta), is discovered. Its inclusion into the theory allows one to improve substantially the agreement with experimental data in the description of energies and transition probabilities of scissors modes in rare-earth nuclei.

Background: The cross sections for populating the residual nucleus in the reaction ${}_Z^A\text{X}{(n,x)}_{Z-2}^{A-4}\text{Y}$ exhibit peaks as a function of incident neutron energy corresponding to the ($n,n^{\prime }\alpha$) reaction and, at higher energy, to the ($n,2p3n$) reaction. The relative magnitudes of these peaks vary with the $Z$ of the target nucleus.

Purpose: Study fast neutron-induced reactions on ${}^{60}\text{Ni}$. Locate experimentally the nuclear charge region along the line of stability where the cross sections for $\alpha$ emission and for $2p2n$ emission in fast neutron-induced reactions are comparable as a further test of reaction models.

Methods: Data were taken by using the Germanium Array for Neutron-Induced Excitations. The broad-spectrum pulsed neutron beam of the Los Alamos Neutron Science Center's Weapons Neutron Research facility provided neutrons in the energy range from 1 to 250 MeV. The time-of-flight technique was used to determine the incident-neutron energies.

Results: Absolute partial cross sections for production of seven discrete Fe $\gamma$ rays populated in ${}^{60}\text{Ni}(n,\alpha /2pxn\gamma )$ reactions with $2\le x\le 5$ were measured for neutron energies $1\text{MeV}<E_n<250\text{MeV}$. Hauser–Feshbach plus pre-equilibrium theoretical calculations are compared to the experimental results.

Conclusions: There is good agreement between experimental results and theoretical predictions at lower neutron energies while discrepancies appear at higher neutron energies. The cross section for producing an isotope in fast neutron-induced reactions on stable targets via $\alpha$ emission at the peak of the ($n,\alpha$) and ($n,n^{\prime }\alpha$) reactions is comparable to that for $2p2n$ and $2p3n$ emission at higher incident energies in the nuclear charge region around Fe.

Background: Until now the knowledge about nucleon resonances with a mass higher than 2 GeV has been scarce. Huge amounts of experimental data of the multipion photoproduction have been accumulated, and more can be expected in the future in facilities such as JLab 12 GeV. It makes it possible to investigate the decay of a nucleon resonance into another nucleon resonance.

Purpose: The possibility to research the decay of the $N\left(2120\right)$ to nucleon resonances near 1.7 GeV in the three-pion photoproduction will be explored to provide useful information for future experimental study.

Method: The pion and radiative decay amplitudes of nucleon resonances are studied within the constituent quark model, which is used to calculate the couplings constants, especially for the decay of a nucleon resonance near 2.1 GeV to another nucleon resonance near 1.7 GeV. The three-pion photoproduction off the neutron target, i.e.,$\gamma n\to {\pi }^{-}{\pi }^{-}{\mathrm{\Delta }}^{++}\to {\pi }^{-}{\pi }^{-}{\pi }^{+}p$, is investigated based on the effective Lagrangian method with the coupling constant obtained form the decay amplitudes.

Results: The resonance contribution with a state $N{(}^2{P}_M){\frac{3}{2}}^{-}$ near 2.1 GeV decaying to a state $N{(}^4{P}_M){\frac{5}{2}}^{-}$ near 1.7 GeV, i.e., $N\left(2120\right)\to N\left(1675\right)\pi$, is dominant in the process considered. The total cross section from the resonance contribution is at the order of 1 $\mu \mathrm{b}$ and can be easily distinguished from the background.

Conclusions: Our results suggest it is practicable to research the decay of the $N\left(2120\right)$ to the $N\left(1675\right)$ in experiment.

Background: The spatial distribution of charge and magnetization within the proton is encoded in the elastic form factors. These have been precisely measured in elastic electron scattering, and the combination of proton and neutron form factors allows for the separation of the up- and down-quark contributions.

Purpose: In this work, we extract the proton and neutron form factors from worldwide data with an emphasis on precise new data covering the low-momentum region, which is sensitive to the large-scale structure of the nucleon. From these, we separate the up- and down-quark contributions to the proton form factors.

Method: We combine cross section and polarization measurements of elastic electron-proton scattering to separate the proton form factors and two-photon exchange (TPE) contributions. We combine the proton form factors with parametrization of the neutron form factor data and uncertainties to separate the up- and down-quark contributions to the proton's charge and magnetic form factors.

Results: The extracted TPE corrections are compared to previous phenomenological extractions, TPE calculations, and direct measurements from the comparison of electron and positron scattering. The flavor-separated form factors are extracted and compared to models of the nucleon structure.

Conclusions: With the inclusion of the precise new data, the extracted TPE contributions show a clear change of sign at low $Q^2$, which is necessary to explain the high-$Q^2$ form factor discrepancy while being consistent with the known $Q^2\to 0$ limit. We find that the new Mainz data yield a significantly different result for the proton magnetic form factor and its flavor-separated contributions. We also observe that the rms radius of both the up- and down-quark distributions are smaller than the rms charge radius of the proton.

The prospects for the synthesis of superheavy nuclei (SHN) using radioactive beams are evaluated quantitatively within the framework of a dinuclear system (DNS) concept. The evaporation-residue cross section (ERCS) for the hot fusion reactions are investigated systematically and compared with the recent results obtained by Loveland [Phys. Rev. C 76, 014612 (2007)]. In most cases the intensities of radioactive beams are significantly less than those of the stable beams, therefore using stable beams is predicted to be the most favorable method for producing SHN.

Nonmonotonic (NM) nucleus-nucleus potentials from the energy-density functional (EDF) theory including the Pauli principle have been considered for the nuclear incompressibility $K$ in the range 188–266 MeV. The experimental cross sections of the ${}^{16}\text{O}+{}^{16}\text{O}$ elastic scattering over the 31–350 MeV incident energies have been analyzed in the optical model using the NM potentials. Sensitivity of $K$ on the elastic scattering data is studied and its value for infinite cold nuclear matter deduced to be $222\pm 5\mathrm{MeV}$.