Ultracold neutron (UCN) storage measurements were made in a trap constructed from a 1.3-T Halbach octupole permanent (HOPE) magnet array aligned vertically, using the TES port of the PF2 source at the Institut Laue-Langevin. A mechanical UCN valve at the bottom of the trap was used for filling and emptying. This valve was covered with Fomblin grease to induce nonspecular reflections and was used in combination with a movable polyethylene UCN remover inserted from the top for cleaning of above-threshold UCNs. Loss from UCN depolarization was suppressed with a minimum 2-mT bias field. Without using the UCN remover, a total storage time constant of $(712\pm 19)\mathrm{s}$ was observed; with the remover inserted for 80 s and used at either 80 cm or 65 cm from the bottom of the trap, time constants of $(824\pm 32)\mathrm{s}$ and $(835\pm 36)\mathrm{s}$ were observed. Combining the latter two values, a neutron lifetime of ${\tau }_{\mathrm{n}}=(887\pm 39)\mathrm{s}$ is extracted after primarily correcting for losses at the UCN valve. The time constants of the UCN population during cleaning were observed and compared to calculations based on kinetic theory as well as Monte Carlo studies. These calculations are used to predict above-threshold populations of $\sim 5\%,\sim 0.5\%$, and $\sim {10}^{-12}\%$ remaining after cleaning in the no-remover, 80-cm remover, and 65-cm remover measurements. Thus, by using a nonspecular reflector covering the entire bottom of the trap and a remover at the top of the trap, we have established an effective cleaning procedure for removing a major systematic effect in high-precision ${\tau }_{\mathrm{n}}$ experiments with magnetically stored UCNs.

Competitive effects of nuclear deformation and density dependence of $\mathrm{\Lambda }N$ interaction in $\mathrm{\Lambda }$ binding energies $B_{\mathrm{\Lambda }}$ of hypernuclei are studied systematically on the basis of the baryon-baryon interaction model ESC (extended soft core) including many-body effects. By using the $\mathrm{\Lambda }N$ $G$-matrix interaction derived from ESC, we perform microscopic calculations of $B_{\mathrm{\Lambda }}$ in $\mathrm{\Lambda }$ hypernuclei within the framework of the antisymmetrized molecular dynamics under the averaged-density approximation. The calculated values of $B_{\mathrm{\Lambda }}$ reproduce experimental data within a few hundred keV in the wide mass regions from 9 to 51. It is found that competitive effects of nuclear deformation and density dependence of $\mathrm{\Lambda }N$ interaction work decisively for fine-tuning of $B_{\mathrm{\Lambda }}$ values.

We study dynamic features of a plasma consisting of gluons whose infrared dynamics is improved by the Gribov-Zwanziger quantization. This approach embodies essential features of color confinement which set the plasma apart from conventional quasiparticle systems in several aspects. Our study focusses on a boost-invariant expansion for in- and out-of-equilibrium settings within a momentum-independent relaxation time approximation, which at late times can be characterized by the sound velocity $c_s$, and the shear $\eta$ and bulk $\zeta$ viscosities. We obtain explicit expressions for the transport coefficients $\eta$ and $\zeta$ and check that they are consistent with the numerical solutions of the kinetic equation. At high temperature, keeping also the Gribov parameter constant, we find a scaling $\zeta /\eta \propto 1/3-c_s^2$ which manifests strong breaking of conformal symmetry in contrast to the case of weakly coupled plasmas.

We study the effect of thermal blurring caused by the use of (momentum-space) rapidity as a proxy of coordinate-space rapidity in experimental measurements of conserved-charge fluctuations in relativistic heavy-ion collisions. In theoretical studies assuming statistical mechanics, calculated fluctuations are those in a spatial volume. Experiments, on the other hand, can measure fluctuations only in a momentum space in the final state. In a standard argument to compare experimental results for a momentum space with theoretical studies for a coordinate space, rapidities of particles are implicitly regarded as equivalent to their coordinate-space rapidity. We show that the relation of two fluctuations is significantly altered by the existence of the thermal motion, i.e., thermal blurring. We discuss that the thermal blurring can be regarded as a part of the diffusion process, and the effect can be understood by studying the rapidity window dependences of fluctuations. Centrality dependence of the thermal blurring effect is also discussed.

Minor extensions of the soft-wall model are used to accommodate two variants of Regge trajectories of vector meson excitations. At nonzero temperatures, various options for either sequential or instantaneous disappearance of vector mesons as normalizable modes are found, thus emulating deconfinement at a certain temperature in the order of the (pseudo)critical temperature of QCD. The crucial role of the blackness function, which steers the thermodynamic properties of the considered system, is highlighted.

Background: The two-nucleon momentum distributions of nucleons $N_1$ and $N_2$ in a nucleus $A, n_A^{N_1{N}_2}({\mathbf{k}}_{\mathrm{rel}},{\mathbf{K}}_{\mathrm{c}.\mathrm{m}.})$, is a relevant quantity that determines the probability of finding two nucleons with relative momentum ${\mathbf{k}}_{\mathrm{rel}}$ and center-of-mass (c.m.) momentum ${\mathbf{K}}_{\mathrm{c}.\mathrm{m}.}$; at high values of the relative momentum and, at the same time, low values of the c.m. momentum, $n_A^{N_1{N}_2}({\mathbf{k}}_{\mathrm{rel}},{\mathbf{K}}_{\mathrm{c}.\mathrm{m}.})$ provides information on the short-range structure of nuclei.

Purpose: Our purpose is to calculate the momentum distributions of proton-neutron and proton-proton pairs in ${}^3\mathrm{He}, {}^4\mathrm{He}, {}^{12}\mathrm{C}, {}^{16}\mathrm{O}$, and ${}^{40}\mathrm{Ca}$, in correspondence to various values of ${\mathbf{k}}_{\mathrm{rel}}$ and ${\mathbf{K}}_{\mathrm{c}.\mathrm{m}.}$.

Methods: The momentum distributions for $A>4$ nuclei are calculated as a function of the relative, $k_{\text{rel}}$, and center-of-mass, $K_{\text{c.m.}}$, momenta and relative angle $\mathrm{\Theta }$, within a linked cluster many-body expansion approach, based upon realistic local two-nucleon interaction of the Argonne family and variational wave functions featuring central, tensor, and spin-isospin correlations.

Results: Independently of the mass number $A$, at values of the relative momentum $k_{\text{rel}}\gtrsim 1.5–2 {\mathrm{fm}}^{-1}$ the momentum distributions exhibit the property of factorization, $n_A^{N_1{N}_2}({\mathbf{k}}_{\mathrm{rel}},{\mathbf{K}}_{\mathrm{c}.\mathrm{m}.})\simeq n_{\mathrm{rel}}^{N_1{N}_2}\left(k_{\mathrm{rel}}\right)n_{\mathrm{c}.\mathrm{m}.}^{N_1{N}_2}\left(K_{\mathrm{c}.\mathrm{m}.}\right)$; in particular, for $pn$ back-to-back pairs one has $n_A^{pn}(k_{\mathrm{rel}},K_{\mathrm{c}.\mathrm{m}.}=0)\simeq C_A^{pn}{n}_D\left(k_{\mathrm{rel}}\right)n_{\mathrm{c}.\mathrm{m}.}^{pn}(K_{\mathrm{c}.\mathrm{m}.}=0)$, where $n_D$ is the deuteron momentum distribution, $n_{\mathrm{c}.\mathrm{m}.}^{pn}(K_{\mathrm{c}.\mathrm{m}.}=0)$ the c.m. motion momentum distribution of the pair, and $C_A^{pn}$ the $pn$ nuclear contact measuring the number of back-to-back $pn$ pairs with deuteron-like momenta (${\mathbf{k}}_p\simeq -{\mathbf{k}}_n,{\mathbf{K}}_{\mathrm{c}.\mathrm{m}.}=0$).

Conclusions: The values of the $pn$ nuclear contact are extracted from the general properties of the two-nucleon momentum distributions corresponding to $K_{\mathrm{c}.\mathrm{m}.}=0$. The $K_{\mathrm{c}.\mathrm{m}.}$-integrated $pn$ momentum distributions exhibit the property $n_A^{pn}\left(k_{\mathrm{rel}}\right)\simeq C_A^{pn}{n}_D\left(k_{\mathrm{rel}}\right)$ but only at very high values of $k_{\mathrm{rel}}, \gtrsim 3.5–4 {\mathrm{fm}}^{-1}$. The theoretical ratio of the $pp/pn$ momentum distributions of ${}^4\mathrm{He}$ and ${}^{12}\mathrm{C}$ and the calculated c.m. motion momentum distributions are in agreement with recent experimental data.

Motivated by a recent work performed at Australian National University by S. Kalkal et al. [Phys. Rev. C 93, 044605 (2016)] on breakup and its time scale, where it was shown that the prompt (or near-target) breakup of ${}^{6,7}\mathrm{Li}$ is almost negligible and consequently the near-barrier complete fusion cross section induced by these weakly bound Li isotopes on light targets should not be suppressed by the breakup, as it is for heavier targets, we estimated the contributions of complete and incomplete fusion in the measured total fusions for several light systems available in the literature. The chosen systems were those for which the fusion cross sections had been measured using the $\gamma$-ray spectroscopy method and all evaporation channel cross sections were reported. For the estimation, we used, apart from the data, the predictions of the evaporation code cascade. The results show that, indeed, the complete fusion suppression is negligible for such systems at energies slightly above the barrier, in agreement with the above-mentioned recent measurements of breakup time scales.

The possibilities of direct production of the isotopes of transfermium nuclei ${}^{259,260}\mathrm{Md}, {}^{260,261}\mathrm{No}, {}^{261–264}\mathrm{Lr}, {}^{264,265}\mathrm{Rf}, {}^{264–268}\mathrm{Db}, {}^{266–269}\mathrm{Sg}, {}^{266–271}\mathrm{Bh}, {}^{267–274}\mathrm{Hs}$, and ${}^{270–274}\mathrm{Mt}$ in various asymmetric hot fusion-evaporation reactions are studied. The excitation functions of the formation of these isotopes in the $\alpha xn$ and $pxn$ evaporation channels are predicted for the first time. The optimal reaction partners and conditions for the synthesis of new isotopes are suggested. The products of the suggested reactions can fill a gap of unknown isotopes between the isotopes of heaviest nuclei obtained in the $xn$ evaporation channels of the cold and hot complete fusion reactions.

Multineutron systems are crucial to understanding the physics of neutron-rich nuclei and neutron stars. Neutron drops, neutrons confined in an external field, are investigated systematically in both nonrelativistic and relativistic density functional theories and with ab initio calculations. We demonstrate a new strong linear correlation, which is universal in the realm of mean-field models, between the rms radii of neutron drops and the neutron skin thickness of ${}^{208}\mathrm{Pb}$ and ${}^{48}\mathrm{Ca}$, i.e., the difference between the neutron and proton rms radii of a nucleus. Due to its high quality, this correlation can be used to deduce the radii of neutron drops from the measured neutron skin thickness in a model-independent way, and the radii obtained for neutron drops can provide a useful constraint for realistic three-neutron forces. We also present a new correlation between the slope $L$ of the symmetry energy and the radii of neutron drops, and provide the first validation of such a correlation by using density-functional models and ab initio calculations. These newly established correlations, together with more precise measurements of the neutron skin thicknesses of ${}^{208}\mathrm{Pb}$ and ${}^{48}\mathrm{Ca}$ and/or accurate determinations of $L$, will have an enduring impact on the understanding of multineutron interactions, neutron-rich nuclei, neutron stars, etc.

Lifetime measurements of yrast levels in ${}^{167}\mathrm{W}$ were measured using the recoil-distance Doppler-shift method. The differential decay-curve method was applied for a lifetime determination. Excited states of the nucleus ${}^{167}\mathrm{W}$ were populated by the reaction ${}^{142}\mathrm{Nd}$ (${}^{28}\mathrm{Si}, 3n$) at a beam energy of 144 MeV. The energy spectra and measured transition quadrupole moments inferred from the lifetimes of ${}^{167}\mathrm{W}$ are compared with the predictions of the cranked Nilsson-Strutinsky-Bogoliubov calculations. The changes of deformations and shapes with increasing spin due to the $\gamma$-polarization effect of aligned particles are discussed. The signature inversion visible in the negative parity yrast band is explained to be related to the triaxial shapes.

The properties of nuclear matter and finite nuclei are studied within the quark mean field (QMF) model by taking the effects of pions and gluons into account at the quark level. The nucleon is described as the combination of three constituent quarks confined by a harmonic oscillator potential. To satisfy the spirit of QCD theory, the contributions of pions and gluons on the nucleon structure are treated in second-order perturbation theory. In a nuclear many-body system, nucleons interact with each other by exchanging mesons between quarks. With different constituent quark mass, $m_q$, we determine three parameter sets for the coupling constants between mesons and quarks, named QMF-NK1, QMF-NK2, and QMF-NK3, by fitting the ground-state properties of several closed-shell nuclei. It is found that all of the three parameter sets can give a satisfactory description of properties of nuclear matter and finite nuclei, moreover they also predict a larger neutron star mass around $2.3M_{\odot }$ without hyperon degrees of freedom.

Background: Interaction of weakly bound heavy ions with an intermediate or heavy target is not yet understood completely due to the scarcity of experimental data. In order to develop a clear understanding of breakup fusion or preequilibrium emission even in the low energy range, 3–10 MeV/nucleon, more experimental investigations are necessary.

Purpose: We aim to study the reaction mechanisms involved in the weakly bound heavy-ion induced reaction ${}^7\mathrm{Li}+{}^{93}\mathrm{Nb}$ at low energies by measuring the production cross sections of the residual radionuclides.

Method: Natural niobium (${}^{93}\mathrm{Nb}$) foil, backed by an aluminum (Al) catcher, arranged in a stack was bombarded by ${}^7\mathrm{Li}$ ions of 20–45 MeV energy. Activity of the residues produced in each ${}^{93}\mathrm{Nb}$ target was measured by off line $\gamma$-ray spectrometry after the end of bombardment (EOB) and cross sections were calculated. Experimental cross sections were compared with those computed using compound and precompound models.

Results: In general, measured excitation functions of all residues produced in the ${}^7\mathrm{Li}+{}^{93}\mathrm{Nb}$ reaction showed good agreement with the model calculations based on the Hauser-Feshbach formalism and the exciton model for compound and precompound processes, respectively. Significant preequilibrium emission of neutrons was observed at the relatively high energy tail of the excitation function of ${}^{97}\mathrm{Ru}$.

Conclusions: Preequilibrium processes played an important role in the enhancement of the cross section in the $xn$ reaction channel over the compound reaction mechanism at higher energies for the ${}^7\mathrm{Li}+{}^{93}\mathrm{Nb}$ reaction. Additionally, indirect evidence of incomplete or breakup fusion was also perceived.

The ${}^{120}\mathrm{Sn}(p,p\alpha ){}^{116}\mathrm{Cd}$ reaction at 392 MeV is investigated with the distorted wave impulse approximation (DWIA) framework. We show that this reaction is very peripheral, mainly because of the strong absorption of $\alpha$ by the reaction residue ${}^{116}\mathrm{Cd}$, and the $\alpha$ clustering on the nuclear surface can be probed clearly. We investigate also the validity of the so-called factorization approximation that has frequently been used so far. It is shown that the kinematics of $\alpha$ in the nuclear interior region is significantly affected by the distortion of ${}^{116}\mathrm{Cd}$, but it has no effect on the reaction observables because of the strong absorption in that region.

We derive an analytic formula for electric and magnetic fields produced by a moving charged particle in a conducting medium with the electric conductivity $\sigma$ and the chiral magnetic conductivity ${\sigma }_{\chi }$. We use the Green's function method and assume that ${\sigma }_{\chi }$ is much smaller than $\sigma$. The compact algebraic expressions for electric and magnetic fields without any integrals are obtained. They recover the Lienard–Wiechert formula at vanishing conductivities. Exact numerical solutions are also found for any values of $\sigma$ and ${\sigma }_{\chi }$ and are compared with analytic results. Both numerical and analytic results agree very well for the scale of high-energy heavy ion collisions. The spacetime profiles of electromagnetic fields in noncentral $\text{Au}+\text{Au}$ collisions have been calculated based on these analytic formula as well as exact numerical solutions.

Using an anomalous transport model for massless quarks and antiquarks, we study the effect of a magnetic field on the elliptic flows of quarks and antiquarks in relativistic heavy ion collisions. With initial conditions from a blast wave model and assuming that the strong magnetic field produced in noncentral heavy ion collisions can last for a sufficiently long time, we obtain an appreciable electric quadrupole moment in the transverse plane of a heavy ion collision. The electric quadrupole moment subsequently leads to a splitting between the elliptic flows of quarks and antiquarks. The slope of the charge asymmetry dependence of the elliptic flow difference between positively and negatively charged particles is positive, which is expected from the chiral magnetic wave formed in the produced QGP and observed in experiments at the BNL Relativistic Heavy Ion Collider, only if the Lorentz force acting on the charged particles is neglected and the quark-antiquark scattering is assumed to be dominated by the chirality changing channel.

Background: The synthesis of heavy, proton rich isotopes in the astrophysical $\gamma$ process proceeds through photodisintegration reactions. For the improved understanding of the process, the rates of the involved nuclear reactions must be known. The reaction ${}^{128}\mathrm{Ba}(\gamma ,\alpha ){}^{124}\mathrm{Xe}$ was found to affect the abundance of the $p$ nucleus ${}^{124}\mathrm{Xe}$ in previous rate variation studies.

Purpose: Since the stellar rate for this reaction cannot be determined by a measurement directly, the aim of the present work was to measure the cross section of the inverse ${}^{124}\mathrm{Xe}(\alpha ,\gamma ){}^{128}\mathrm{Ba}$ reaction and to compare the results with statistical model predictions used in astrophysical networks. Modified nuclear input can then be used to provide an improved stellar reaction rate. Of great importance is the fact that data below the $(\alpha ,n)$ threshold was obtained. Studying simultaneously the ${}^{124}\mathrm{Xe}(\alpha ,n){}^{127}\mathrm{Ba}$ reaction channel at higher energy allowed to further identify the source of a discrepancy between data and prediction.

Method: The ${}^{124}\mathrm{Xe}(\alpha ,\gamma ){}^{128}\mathrm{Ba}$ and ${}^{124}\mathrm{Xe}(\alpha ,n){}^{127}\mathrm{Ba}$ cross sections were measured with the activation method using a thin window ${}^{124}\mathrm{Xe}$ gas cell and an $\alpha$ beam from a cyclotron accelerator. The studied energy range was between $E_{\alpha }=11$ and 15 MeV close above the astrophysically relevant energy range.

Results: The obtained cross sections are compared with Hauser-Feshbach statistical model calculations. The experimental cross sections are smaller than standard predictions previously used in astrophysical calculations. As a dominating source of the difference, the theoretical $\alpha$ width was identified. The experimental data suggest an $\alpha$ width lower by at least a factor of 0.125 in the astrophysically important energy range.

Conclusions: An upper limit for the ${}^{128}\mathrm{Ba}(\gamma ,\alpha ){}^{124}\mathrm{Xe}$ stellar rate was inferred from our measurement. The impact of this rate and lower rates was studied in two different models for core-collapse supernova explosions of 25 $M_{\odot }$ stars. A significant contribution to the ${}^{124}\mathrm{Xe}$ abundance via this reaction path would only be possible when the rate was increased above the previous standard value. Since the experimental data rule this out, they also demonstrate the closure of this production path.

Valuable theoretical predictions of nuclear dipole excitations in the whole chart are of great interest for different nuclear applications, including in particular nuclear astrophysics. Here we extend our large-scale calculations of the $E1 \gamma$-ray strength function, obtained in the framework of the axially- symmetric-deformed quasiparticle random phase approximation (QRPA) based on the finite-range D1M Gogny force, to the calculation of the $M1$ strength function. We compare our QRPA prediction of the $M1$ strength with available experimental data and show that a relatively good agreement is obtained provided the strength is shifted globally by about 2 MeV and increased by an empirical factor of 2. Predictions of the $M1$ strength function for spherical and deformed nuclei within the valley of $\beta$ stability as well as in the neutron-rich region are discussed. Its impact on the radiative neutron capture cross section is also analyzed.

Nuclear fission is treated by using the Langevin dynamical description with macroscopic and microscopic transport coefficients (mass and friction tensors), and it is elucidated how the microscopic (shell and pairing) effects in the transport coefficients, especially their dependence on temperature, affects various fission observables. We found that the microscopic transport coefficients, calculated by linear response theory, change drastically as a function of temperature: in general, the friction increases with growing temperature while the mass tensor decreases. This temperature dependence brings a noticeable change in the mass distribution and kinetic energies of fission fragments from nuclei around ${}^{236}\mathrm{U}$ at an excitation energy of 20 MeV. The prescission kinetic energy decreases from 25 MeV at low temperature to about 2.5 MeV at high temperature. In contrast, the Coulomb kinetic energy increases as the temperature increases. Interpolating the microscopic transport coefficients among the various temperatures enabled our Langevin equation to use the microscopic transport coefficients at a deformation-dependent local temperature of the dynamical evolution. This allowed us to compare directly the fission observables of both macroscopic and microscopic calculations, and we found almost identical results under the conditions considered in this work.

Spectral functions of the nucleon and its negative-parity excited state in nuclear matter are studied by using QCD sum rules and the maximum entropy method (MEM). It is found that in-medium modifications of the spectral functions are attributed mainly to density dependencies of the $\langle \overline{q}q\rangle$ and $\langle q^{†}q\rangle$ condensates. The MEM reproduces the lowest-energy peaks of both the positive- and negative-parity nucleon states at finite density up to $\rho \sim {\rho }_N$ (normal nuclear matter density). As the density grows, the residue of the nucleon ground state decreases gradually while the residue of the lowest negative-parity excited state increases slightly. On the other hand, the positions of the peaks, which correspond to the total energies of these states, are almost density independent for both parity states. The density dependencies of the effective masses and vector self-energies are also extracted by assuming phenomenological mean-field-type propagators for the peak states. We find that, as the density increases, the nucleon effective mass decreases while the vector self-energy increases. The density dependence of these quantities for the negative-parity state on the other hand turns out to be relatively weak.

A new method to calculate spectroscopic properties of deformed nuclei is proposed: configuration interaction on top of projected density functional theory (CI-PDFT). The general concept of this approach is discussed in the framework of covariant density functional theory and its validity is illustrated in an application to the yrast band of the nucleus ${}^{54}\mathrm{Cr}$. It is found that the experimentally observed excitation energies for the yrast band in ${}^{54}\mathrm{Cr}$ can be well reproduced. In contrast to conventional shell-model calculations, there is no core and only a relatively small number of configurations is sufficient for a satisfying description. No new parameters are necessary, because the effective interaction is derived from an universal density functional given in the literature.