We argue that the observation of the color-transparency effect in the semiexclusive $A({\pi }^{-},l^{+}{l}^{-})$ process is important for determining whether it is possible to extract the generalized parton distributions of the nucleon from the elementary reaction ${\pi }^{-}p\to l^{+}{l}^{-}n$ at $p_{\mathrm{lab}}=15–20$ GeV/$c$ at small $\left|t\right|$ and large invariant mass of the dilepton pair $l^{+}{l}^{-}$. Assuming that the transverse size of the pionic $q\overline{q}$ pair in the hard interaction point is similar to the one in the reaction ${\gamma }^{*}p\to {\pi }^{+}n$ studied at JLab, we predict large color-transparency effects in the discussed kinematic range. We also suggest that the semiexclusive ${\rho }^0$ production in ${\pi }^{-}$-induced reactions in the same beam momentum region may provide new information on the dynamics of the interaction in the nonvacuum channel, while the $J/\psi$ production can be used to get information on $J/\psi N$ total interaction cross section.

We discuss quantized vortices in neutron ${}^{3}P_2$ superfluids, which are believed to realize in high density neutron matter such as neutron stars. By using the Ginzburg-Landau free energy for ${}^{3}P_2$ superfluids, we determine the ground state in the absence and presence of the external magnetic field, and numerically construct ${}^{3}P_2$ quantized vortices in the absence and presence of the external magnetic field along the vortex axis (poloidal) or angular direction (toroidal). We find in certain situations the spontaneous magnetization of the vortex core, whose typical magnitude is about ${10}^{7–8}$ G, but the net magnetic field in a neutron star is negligible because of the ratio of the vortex core size $\sim 10\mathrm{fm}$ and the intervortex distance $\sim {10}^{-6}\mathrm{m}$ in a vortex lattice.

The emergence and evolution of collective excitations in complex nuclei remains a central problem in the quest to understand the nuclear many-body problem. Nuclear quadrupole collectivity is usually investigated via electric quadrupole observables. Here, however, we measure the $g$ factors of low-excitation states in ${}^{111}\mathrm{Cd}$ and ${}^{113}\mathrm{Cd}$ and show that they are sensitive to the nature of the collectivity in these nuclei in ways that the electric quadrupole observables are not. The particle-vibration model, which assumes spherical core excitations, cannot explain the $g$ factors, whereas a particle-rotor model with a small, nonzero core deformation does. The contrast of the two models is made stark by the fact that they begin from the same limiting $g$-factor values: It is shown that when an odd nucleon occupies a spherical orbit with angular momentum $j=1/2$, or a deformed orbit with $j=1/2$ parentage, the particle-vibration model and the particle-rotor model both reduce to the same $g$-factor value in their respective limits of zero particle-vibration coupling or zero deformation.

Background: The recently started physics campaign with the new generation of $\gamma$-ray spectrometers, “GRETINA” and “AGATA,” will possibly produce many high-quality $\gamma$ rays from very fast-rotating nuclei. Microscopic models are needed to understand these states.

Purpose: It is a theoretical challenge to describe high-spin states in a shell-model framework by the concept of configuration mixing. To meet the current needs, one should overcome the present limitations and vigorously extend the quasiparticle (qp) basis of the projected shell model (PSM).

Method: With the help of the recently proposed Pfaffian formulas, we apply the new algorithm and develop a new PSM code that extends the configuration space to include up to 10-qp states. The much-enlarged multi-qp space enables us to investigate the evolutional properties at very high spins in fast-rotating nuclei.

Results: We take ${}^{134}\mathrm{Nd}$ as an example to demonstrate that the known experimental yrast and the several negative-parity side bands in this nucleus could be well described by the calculation. The variations in moment of inertia with spin are reproduced and explained in terms of successive band crossings among the 2-qp, 4-qp, 6-qp, 8-qp, and 10-qp states. Moreover, the electric quadrupole transitions in these bands are studied.

Conclusions: A pronounced decrease in the high-spin $B\left(E2\right)$ of ${}^{134}\mathrm{Nd}$ is predicted, which suggests reduction of collectivity at very high spins because of increased level density and complex band mixing. The possibility for a potential application of the present development in the study of highly excited states in warm nuclei is mentioned.

The $B\left(E2\right)$ excitation strength of the first excited $2^{+}$ state in even-even nuclei should directly correlate with the size of the valence space and maximize at mid-shell. A previously found saturation of $B\left(E2\right)$ strengths in well-deformed rotors at mid-shell is tested through high-precision measurements of the lifetimes of the lowest-lying $2^{+}$ states of the ${}^{168}\text{Hf}$ and ${}^{174}\text{W}$ rare earth isotopes. Measurements were performed using fast ${\mathrm{LaBr}}_3$ scintillation detectors. Combined with the recently remeasured $B(E2;2_1^{+}\to 0_1^{+})$ values for Hf and W isotopes the new data remove discrepancies observed in the differentials of $B\left(E2\right)$ values for these isotopes.

We investigate the azimuthal anisotropy $v_2$ of particle production in nucleus-nucleus collisions in the maximum entropy approach. This necessitates two new phenomenological input parameters $\delta$ and ${\lambda }_2$ compared with integrated multiplicity distributions. The parameter $\delta$ describes the deformation of a flux tube and can be theoretically calculated in a bag model with a bag constant which depends on the density of surrounding flux tubes. The parameter ${\lambda }_2$ defines the anisotropy of the particle distribution in momentum space and can be connected to $\delta$ via the uncertainty relation. In this framework we compute the anisotropy $v_2$ as a function of centrality, transverse momentum, and rapidity in qualitative agreement with Large Hadron Collider data.

We study the compositeness of near-threshold quasibound states in the framework of effective field theory. From the viewpoint of the low-energy universality, we revisit the model-independent relations between the structure of the bound state and the observables in the weak binding limit. The effective field theory enables us to generalize the weak-binding relation of the stable bound states to unstable quasibound states with decay modes. We present the interpretation of the complex values of the compositeness for the unstable states. Combining the model-independent relation and the threshold observables extracted from the experimental data, we show that $\mathrm{\Lambda }\left(1405\right)$ is dominated by the $\overline{K}N$ molecular structure and that $a_0\left(980\right)$ is dominated by the non-$\overline{K}K$ component.

Background: The sharp $1^{-}$ resonances with enhanced isoscalar dipole transition strengths are observed in many light nuclei at relatively small excitation energies, but their nature has been unclear.

Purpose: We show those resonances can be attributed to the cluster states with asymmetric configurations such as $\alpha +{}^{16}\mathrm{O}$. We explain why asymmetric cluster states are strongly excited by the isoscalar dipole transition. We also provide a theoretical prediction of the isoscalar dipole transitions in ${}^{20}\mathrm{Ne}$ and ${}^{44}\mathrm{Ti}$.

Method: The transition matrix is analytically derived to clarify the excitation mechanism. The nuclear model calculations by Brink–Bloch wave function and antisymmetrized molecular dynamics are also performed to provide a theoretical prediction for ${}^{20}\mathrm{Ne}$ and ${}^{44}\mathrm{Ti}$.

Results: It is shown that the transition matrix is as large as the Weisskopf estimate even though the ground state is an ideal shell-model state. Furthermore, it is considerably amplified if the ground state has cluster correlation. The nuclear model calculations predict large transition matrix to the $\alpha +{}^{16}\mathrm{O}$ and $\alpha +{}^{40}\mathrm{Ca}$ cluster states comparable with or larger than the Weisskopf estimate.

Conclusions: We conclude that the asymmetric cluster states are strongly excited by the isoscalar dipole transition. Combined with the isoscalar monopole transition that populates the $0^{+}$ cluster states, the isoscalar transitions are promising probes for asymmetric clusters.

The formalism of the continuum random-phase approximation theory which treats, without approximations, the continuum part of the single-particle spectrum, is extended to describe charge-exchange excitations. Our approach is self-consistent, meaning that we use a unique, finite-range interaction in the Hartree-Fock calculations which generate the single-particle basis and in the continuum-random phase approximation which describes the excitation. We study excitations induced by the Fermi, Gamow-Teller and spin-dipole operators in doubly magic nuclei by using four Gogny-like finite-range interactions, two of them containing tensor forces. We focus our attention on the importance of the correct treatment of the continuum configuration space and on the effects of the tensor terms of the force.

Background: The giant pairing vibration (GPV), a correlated two-nucleon mode in the second shell above the Fermi surface, has long been predicted and expected to be strongly populated in two-nucleon transfer cross sections similar to those of the normal pairing vibration. Recent experiments have provided evidence for this mode in ${}^{14,15}\text{C}$ but, despite sensitive studies, it has not been definitively identified in either Sn or Pb nuclei where pairing correlations are known to play a crucial role.

Purpose: Our aim is to test whether features inherent to the mixing of bound and unbound levels might account for this and to study the effect in a simple and intuitively clear approach.

Method: We study the mixing of unbound levels in a set of toy models that capture the essential physics of the GPV, along with a more realistic calculation including distorted-wave Born approximation transfer amplitudes.

Results: The calculated (relative) cross section to populate a simulated GPV state is effectively low, compared to the case of bound levels with no widths

Conclusions: The mixing turns out to be only a minor contributor to the weak population. Rather, the main reason is the melting of the GPV peak due to the width it acquires from the low orbital angular momentum single-particle states playing a dominant role in two-nucleon transfer amplitudes. This effect, in addition to a severe $Q$-value mismatch, may account for the elusive nature of this mode in $(t,p)$ and $(p,t)$ reactions.

The neutron-induced fission cross section of ${}^{237}\mathrm{Np}$ was experimentally determined at the high-resolution and high-intensity facility n_TOF, at CERN, in the energy range 100 keV to 9 MeV, using the ${}^{235}\mathrm{U}(n,f)$ and ${}^{238}\mathrm{U}(n,f)$ cross section standards below and above 2 MeV, respectively. A fast ionization chamber was used in order to detect the fission fragments from the reactions and the targets were characterized as far as their mass and homogeneity are concerned by means of $\alpha$ spectroscopy and Rutherford backscattering spectroscopy respectively. Theoretical calculations within the Hauser-Feshbach formalism have been performed, employing the empire code, and the model parameters were tuned in order to successfully reproduce the experimental fission cross-sectional data and simultaneously all the competing reaction channels.

We report the measurement of one-neutron stripping of ${}^9\text{Be}$ to the ${}^{169}\text{Tm},{}^{181}\text{Ta}$, and ${}^{187}\text{Re}$ nuclei, in the range from subbarrier to above-barrier energies. The activation technique was used, with the detection of off-line $\gamma$ rays. The results show that the transfer cross sections for the three systems investigated are very similar and are much larger than the corresponding fusion cross sections at subbarrier energies, whereas fusion predominates at energies above the barrier. Data are in good agreement with our coupled reaction channel calculations. We also investigate the ratio, as a function of energy, between experimental transfer and fusion cross sections. The role of transfer couplings on the fusion excitation functions is also discussed.

We studied the number of constituent quark scaling (NCQ) behavior of elliptic flow $\left(v_2\right)$ under the framework of a multiphase transport model (AMPT) at both top-RHIC and LHC energies. The NCQ-scaling in $v_2$ holds at top RHIC energy with AMPT string melting version, while it breaks in Pb+Pb collisions at LHC energy using the same framework. The breaking of NCQ scaling at LHC energy has been studied by varying the magnitude of parton-parton scattering cross sections and lifetime of hadronic cascade as implemented in AMPT. We find that the breaking of NCQ scaling in Pb+Pb collisions at $\sqrt{s_{\mathit{NN}}}=2.76$ TeV is independent of the magnitude of parton-parton cross sections and the later stage hadronic interactions. Further we observed that scaling holds in a small collision system like Si+Si at $\sqrt{s_{\mathit{NN}}}=2.76$ TeV. We discussed that the breaking of NCQ scaling is possibly due to high phase-space density of constituents quarks in Pb+Pb collisions at $\sqrt{s_{\mathit{NN}}}=2.76$ TeV.

With a multiphase transport (AMPT) model we investigate the relation between the magnitude, fluctuations, and correlations of the initial state spatial anisotropy ${\varepsilon }_n$ and the final state anisotropic flow coefficients $v_n$ in Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV. It is found that the relative eccentricity fluctuations in AMPT account for the observed elliptic flow fluctuations, both are in agreement with the elliptic flow fluctuation measurements from the STAR collaboration. In addition, the studies based on two- and multiparticle correlations and event-by-event distributions of the anisotropies suggest that the elliptic-power function is a promising candidate of the underlying probability density function of the event-by-event distributions of ${\varepsilon }_n$ as well as $v_n$. Furthermore, the correlations between different order symmetry planes and harmonics in the initial coordinate space and final state momentum space are presented. Nonzero values of these correlations have been observed. The comparison between our calculations and data will, in the future, shed new insight into the nature of the fluctuations of the quark-gluon plasma produced in heavy ion collisions.

Medium-spin excited levels in ${}^{90}\mathrm{Rb}$, populated in the fission of ${}^{235}\mathrm{U}$ induced by neutrons, have been observed for the first time. $\gamma$ radiation from fission has been measured by using the EXILL array of Ge detectors at the cold-neutron-beam facility PF1B of the Institut Laue–Langevin, Grenoble. Low-energy levels are interpreted as members of the $\pi p_{3/2}^{-1}\nu {\left(d_{5/2}\right)}^3$, $\pi f_{5/2}^{-1}\nu {\left(d_{5/2}\right)}^3$, and $\pi g_{9/2}\nu {\left(d_{5/2}\right)}^3$ multiplets with the $0^{-}$ ground state due to the seniority-3 coupling in the $\nu d_{5/2}$ shell. Analogous anomalous coupling within the $\pi g_{9/2}\nu {\left(d_{5/2}\right)}^3$ configuration explains the $5^{+}$, $6^{+}$, and $7^{+}$ triplet of states, observed at medium spins, similar to the triplet seen in the $N=53$ isotone, ${}^{88}\mathrm{Br}$. Shell-model calculations reproduce well the proposed structures in ${}^{88,90}\mathrm{Rb}$ and support the seniority-3 coupling in $N=53$ isotones and its absence in $N=51$ isotones. The structure of the odd-odd ${}^{88}\mathrm{Rb}$ and ${}^{90}\mathrm{Rb}$ nuclei provides an argument in favor of the collectivity building up at the neutron number $N=53$.

The role of simultaneous particle emission processes in the evaporation phase is investigated in the high-energy regime of compound nucleus excitation. A Monte Carlo simulation is employed to consider the effect of different emission channels on the particle yield and on the fission process occurrence. A significant change is shown on evaporation-phase results due to the inclusion of multiparticle emission channels in the calculation of the compound nucleus modes of deexcitation. The total yield of neutrons and charged particles suffer an significant change in respect to results obtained in the conventional approach restricted to the sequential one-particle emission mechanism. These particle multiplicities, determined as a function of the excitation energy, present a qualitative change at the high-excitation-energy regime of the compound nucleus. This behavior is confirmed when a different mass formula is used to determine separation and nuclear binding energies. This finding is an important aspect for the study of spallation reaction in acceleration driven system (ADS) reactors, since the majority of neutrons generated in these reactions come from the evaporation stage of the reaction.

Previously reported data for fusion of the ${}^8\mathrm{B}+({}^{58}\mathrm{Ni},{}^{28}\mathrm{Si})$ systems are critically reviewed. New $\alpha \text{-particle}$ data from the fusion of ${}^8\mathrm{B}+{}^{58}\mathrm{Ni}$ also are reported, but the paper is mostly based on using realistic calculations of well-established codes to reanalyze the previous data. The influence of breakup protons on the evaporation proton measurements for the heavier system is found to be small at all energies except for the lowest one measured, and corrections are made for this process. Possible model dependencies in the deduced fusion cross sections are investigated using three different evaporation codes. The data sets for the ${}^{58}\mathrm{Ni}$ and ${}^{28}\mathrm{Si}$ targets are shown to be consistent with each other and with fusion enhancement up to energies that are greater than the Coulomb barrier $V_b$ $(E_{\text{c.m.}}\lesssim {\mathrm{V}}_b+1.5\times \hslash \omega )$. This limit corresponds to 6.2 MeV above the barrier for the ${}^{58}\mathrm{Ni}$ target. An important difference with the behavior of neutron-halo systems is thus confirmed.

$\alpha$ decay is a common and important process of natural radioactivity of heavy and superheavy nuclei. The $\alpha$ decay half-lives for even-even nuclei from $Z=62$ to $Z=118$ are systematically studied based on the two-potential approach with a quasistationary state approximation. As for the nuclear potential, the isospin effect is considered, which slightly improves the results by 6.8%. To reduce the deviations between experimental half-lives and calculated results due to the nuclear shell structure, the analytic expression of hindrance factors is employed. Our results can reproduce the experimental half-lives as good as using the density-dependent cluster model and the generalized liquid drop model.

The structure of ${}^{70}\mathrm{Ge}$ has been studied through in-beam $\gamma$-ray spectroscopy. A new band structure is identified that leads to forking of the ground-state band into two excited bands. Band structures have been investigated using the microscopic triaxial projected shell-model approach. The observed forking is demonstrated to result from almost simultaneous band crossing of the two-neutron aligned configuration and the $\gamma$ band built on this two-quasiparticle configuration with the ground-state band.

Background: Neutrino-driven winds following core-collapse supernova explosions have been proposed as a possible site where light $r\text{-process}$ nuclei (between Fe and Ag) might be synthesized. In these events, $(\alpha ,n)$ reactions are key to moving matter towards the region of higher proton number. Abundance network calculations are very sensitive to the rates for this type of reactions.

Purpose: The present work aims at evaluating the theoretical uncertainty of these $(\alpha ,n)$ reactions calculated with reaction codes based on the Hauser-Feshbach model.

Method: We compared several $\left(\alpha ,n\right)$ rates taken from talys and the non-smoker database to determine the uncertainties owing to the existing technical differences between both codes. In addition, we evaluated the sensitivity of talys rates to variations in the $\alpha$ optical potentials, masses, level densities, optical potentials, preequilibrium intranuclear transition rates, level structure, radiative transmission coefficients, and width-fluctuation correction factors.

Results: The main source of uncertainty at low temperature is mostly attributable to the use of different $\alpha$ optical potentials. Differences between talys and non-smoker at high temperatures arise from the energy-binning algorithm used by each code. We have also noticed that the $\left(\alpha ,n\right)$ rates from the non-smoker database correspond to the inclusive reaction, instead of the exclusive $\left(\alpha ,1n\right)$ channel calculated in the present work and used in network calculations.

Conclusions: Theoretical uncertainties in calculated reaction rates can be as high as one to two orders of magnitude and strongly dependent on the temperature of the environment. Besides direct measurements of the inclusive and exclusive $(\alpha ,1n)$ reaction rates, experimental studies of $\alpha$ optical potentials are crucial to improve the performance of reaction codes.