We study the influence of the ratio of level-density parameters at saddle to that at ground-state configuration ($a_f$/$a_n$) on the sensitivity of fission cross sections (${\sigma }_{\mathrm{fiss}}$) to presaddle dissipation effects by comparing fission excitation functions measured in the ${}^3$He + ${}^{197}$Au (${}^{208}$Pb) reactions with three distinct types of model calculations: the standard Bohr-Wheeler theory with $a_f$/$a_n$ $=$ 1 (i) and $a_f$/$a_n$ $\ne$ 1 (ii) as well as the Langevin approach with $a_f$/$a_n$ $\ne$ 1 (iii). It is shown that both cases (i) and (ii) cannot provide a reasonable, satisfactory description of the measured ${\sigma }_{\mathrm{fiss}}$. A presaddle friction strength ($\beta$) of (4–4.5) $\times$ 10${}^{21}$ s${}^{-1}$ is extracted through reproducing data with Langevin simulations. We find from the comparison of the experimental and calculated ${\sigma }_{\mathrm{fiss}}$ in cases (ii) and (iii) that a precise determination of $\beta$ depends sensitively on $a_f$/$a_n$. The finding indicates that level-density parameters play a significant role in accurately probing presaddle friction; that is, to stringently constrain $\beta$ it is important to take into account a realistic and an elaborate evaluation of $a_f$/$a_n$ in theoretical calculations. We further find that high energy increases the sensitivity of ${\sigma }_{\mathrm{fiss}}$ to $\beta$, suggesting that in experiments, to obtain precise information of presaddle dissipation by measuring ${\sigma }_{\mathrm{fiss}}$, it is best to populate a compound nucleus with high energy.

This paper details the solar neutrino analysis of the 385.17-day phase-III data set acquired by the Sudbury Neutrino Observatory (SNO). An array of ${}^3$He proportional counters was installed in the heavy-water target to measure precisely the rate of neutrino-deuteron neutral-current interactions. This technique to determine the total active ${}^8$B solar neutrino flux was largely independent of the methods employed in previous phases. The total flux of active neutrinos was measured to be $5.{54}_{-0.31}^{+0.33}{\text{(stat.)}}_{-0.34}^{+0.36}\text{(syst.)}\times {10}^6$ cm${}^{-2}$ s${}^{-1}$, consistent with previous measurements and standard solar models. A global analysis of solar and reactor neutrino mixing parameters yielded the best-fit values of $\Delta m^2=7.{59}_{-0.21}^{+0.19}\times {10}^{-5}{\text{eV}}^2$ and $\theta =34.4_{-1.2}^{+1.3}\text{degrees}$.

We calculate the energy per particle in infinite neutron matter perturbatively using chiral N${}^3$LO (next-to-next-to-next-to-leading order) two-body potentials plus N${}^2$LO three-body forces. The cutoff dependence of the predictions is investigated by employing chiral interactions with different regulators. We find that the inclusion of three-nucleon forces, which are consistent with the applied two-nucleon interaction, leads to a strongly reduced regulator dependence of the results.

The half-life of the $I^{\pi }=6^{+}$ yrast state at $E_x=2294$ keV in ${}^{138}$Ce has been measured as $T_{1/2}=880\left(19\right)$ ps using the fast-timing $\gamma$-ray coincidence method with a mixed LaBr${}_3$(Ce)-HPGe array. The excited states in ${}^{138}$Ce have been populated by the ${}^{130}$Te(${}^{12}\mathrm{C},4n)$ fusion-evaporation reaction at an incident beam energy of 56 MeV. The extracted $B(E2;6_1^{+}\to 4_1^{+})=0.101\left(24\right)$ W.u. value is compared with the predictions of truncated basis shell model calculations and with the systematics of the region. This shows an anomalous behavior compared to the neighboring isotonic and isotopic chains. Half-lives for the yrast 5${}^{-}$, 11${}^{+}$ and 14${}^{+}$ states in ${}^{138}$Ce have also been determined in this work.

The evolution of massive stars with very low-metallicities depends critically on the amount of CNO nuclides which they produce. The ${}^{12}$N($p,\gamma$)${}^{13}$O reaction is an important branching point in the rap processes, which are believed to be alternative paths to the slow $3\alpha$ process for producing CNO seed nuclei and thus could change the fate of massive stars. In the present work, the angular distribution of the ${}^2$H(${}^{12}$N, ${}^{13}$O)$n$ proton transfer reaction at $E_{\mathrm{c}.\mathrm{m}.}=8.4$ MeV has been measured for the first time. Based on the Johnson-Soper approach, the square of the asymptotic normalization coefficient (ANC) for the virtual decay of ${}^{13}$O${}_{\mathrm{g}}.\mathrm{s}.$ $\to$ ${}^{12}$N+$p$ was extracted to be $3.92\pm 1.47$ fm${}^{-1}$ from the measured angular distribution and utilized to compute the direct component in the ${}^{12}$N($p,\gamma$)${}^{13}$O reaction. The direct astrophysical $S$ factor at zero energy was then found to be $0.39\pm 0.15$ keV b. By considering the direct capture into the ground state of ${}^{13}$O, the resonant capture via the first excited state of ${}^{13}$O and their interference, we determined the total astrophysical $S$ factors and rates of the ${}^{12}$N($p,\gamma$)${}^{13}$O reaction. The new rate is two orders of magnitude slower than that from the REACLIB compilation. Our reaction network calculations with the present rate imply that ${}^{12}$N($p,\gamma$)${}^{13}$O will only compete successfully with the ${\beta }^{+}$ decay of ${}^{12}$N at higher ($\sim 2$ orders of magnitude) densities than initially predicted.

By using the recoil-fission correlation technique, the exotic process of beta-delayed fission ($\beta$DF) was unambiguously identified in the very neutron-deficient nuclei ${}^{192,194}$At in experiments at the velocity filter SHIP at Gesellschaft für Schwerionenforschung (GSI). The upper limits for the total kinetic energy release in fission of ${}^{192,194}$Po, being the daughter products of ${}^{192,194}$At after ${\beta }^{+}/EC$ decay, were estimated. The possibility of an unusually high $\beta$DF probability for ${}^{192}$At is discussed.

By using the technique of correlating implanted evaporation residues and their subsequent fission decay, $\beta$-delayed fission ($\beta$DF) of ${}^{186}$Bi has been identified for the first time and $\beta$DF of ${}^{188}$Bi has been unambiguously confirmed. The experiments were performed at the velocity filter SHIP (GSI, Darmstadt). The $\beta$DF probabilities for both nuclides were qualitatively estimated, and, in particular indications for a large value in the case of ${}^{186}$Bi are regarded.

The level densities and $\gamma$-ray strength functions of ${}^{105,106,111,112}$Cd have been extracted from particle-$\gamma$ coincidence data using the Oslo method. The level densities are in very good agreement with known levels at low excitation energy. The $\gamma$-ray strength functions display no strong enhancement for low $\gamma$ energies. However, more low-energy strength is apparent for ${}^{105,106}$Cd than for ${}^{111,112}$Cd. For $\gamma$ energies above $\approx$4 MeV, there is evidence for some extra strength, similar to what has been previously observed for the Sn isotopes. The origin of this extra strength is unclear; it might be due to $E1$ and $M1$ transitions originating from neutron skin oscillations or the spin-flip resonance, respectively.

Background: Neutrinoless double-$\beta$ decay, if observed, would reveal physics beyond the standard model of particle physics; namely, it would prove that neutrinos are Majorana fermions and that the lepton number is not conserved.

Purpose: The analysis of the results of neutrinoless double-$\beta$ decay observations requires an accurate knowledge of several nuclear matrix elements (NME) for different mechanisms that may contribute to the decay. We provide a complete analysis of these NME for the decay of the ground state (g.s.) of ${}^{48}$Ca to the g.s. $0_1^{+}$ and first excited $0_2^{+}$ state of ${}^{48}$Ti.

Method: For the analysis we used the nuclear shell model with effective two-body interactions that were fine-tuned to describe the low-energy spectroscopy of $pf$-shell nuclei. We checked our model by calculating the two-neutrino transition probability to the g.s. of ${}^{48}$Ti. We also make predictions for the transition to the first excited $0_2^{+}$ state of ${}^{48}$Ti.

Results: We present results for all NME relevant for the neutrinoless transitions to the $0_1^{+}$ and $0_2^{+}$ states, and using the lower experimental limit for the g.s. to g.s. half-life, we extract upper limits for the neutrino physics parameters.

Conclusions: We provide accurate NME for the two-neutrino and neutrinoless double-$\beta$ decay transitions in the $A=48$ system, which can be further used to analyze the experimental results of double-$\beta$ decay experiments when they become available.

Given the importance of Gamow-Teller (GT) transitions in nuclear structure and astrophysical nuclear processes, we have studied $T_z=+3/2\to +1/2$, GT transitions starting from the ${}^{47}$Ti nucleus in the (${}^3\mathrm{He},t$) charge-exchange reaction at $0^{\circ }$ and at an intermediate incident energy of 140 MeV/nucleon. The experiments were carried out at the Research Center for Nuclear Physics (RCNP), Osaka, using the high-resolution facility with a high-dispersion beam line and the Grand-Raiden spectrometer. With an energy resolution of 20 keV, individual GT transitions were observed and GT strength was derived for each state populated up to an excitation energy ($E_x$) of 12.5 MeV. The GT strength was widely distributed from low excitation energy up to 12.5 MeV, where we had to stop the analysis because of the high level density. The distribution of the GT strengths was compared with the results of shell model calculations using the GXPF1 interaction. The calculations could reproduce the experimental GT distributions well. The GT transitions from the ground state of ${}^{47}$Ti and the $M1$ transitions from the isobaric analog state in ${}^{47}$V to the same low-lying states in ${}^{47}$V are analogous. It was found that the ratios of GT transition strengths to the ground state, the 0.088-MeV state, and the 0.146-MeV state are similar to the ratios of the strengths of the analogous $M1$ transitions from the isobaric analog state (IAS) to these states. The measured distribution of the GT strengths was also compared with those starting from the $T_z=+3/2$ nucleus ${}^{41}$K to the $T_z=+1/2$ nucleus ${}^{41}$Ca.

We illustrate the formation of a thin, long structure of heavy nuclei by three-nucleus simultaneous collisions within time-dependent density functional theory. The impact parameter dependence for such a formation is systematically demonstrated through clarifications of the difference between binary and ternary collision events. A new method for producing thin, long heavy nuclei in the laboratory is suggested, as well as the possible formation of the thin, long structure in hot dense matter such as that encountered in core collapse supernovae.

We study $e^{+}{e}^{-}$ pair production in proton-proton and central $\mathrm{Pb}+\mathrm{Pb}$ collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV within two models: an extended statistical hadronization model (SHM) and the Parton-Hadron-String Dynamics (PHSD) transport approach. We find that the PHSD calculations roughly agree with the dilepton spectrum from hadronic sources with the “cocktail” estimates from the statistical hadronization model matched to available data at Large Hadron Collider energies. The dynamical simulations within the PHSD show a moderate increase of the low-mass dilepton yield essentially due to the in-medium modification of the $\rho$ meson. Furthermore, pronounced traces of the partonic degrees of freedom are found in the PHSD results in the intermediate-mass regime. The dilepton production from the strongly interacting quark-gluon plasma (sQGP) exceeds that from the semileptonic decays of open charm and bottom mesons. Additionally, we observe that a transverse momentum cut of 1 GeV/$c$ further suppresses the relative contribution of the heavy-meson decays to the dilepton yield, such that the sQGP radiation strongly dominates the spectrum for masses from 1 to 3 GeV, allowing a closer look at the electromagnetic emissivity of the partonic plasma in the early phase of $\mathrm{Pb}+\mathrm{Pb}$ collisions.

The space-time structure of the multipion system created in central relativistic heavy-ion collisions is investigated. Using the microscopic transport model UrQMD we determine the freeze-out hypersurface from the equation on pion density $n(t,\mathbf{r})=n_c$. It turns out that for proper value of the critical energy density ${\epsilon }_c$ equation $\epsilon (t,\mathbf{r})={\epsilon }_c$ gives the same freeze-out hypersurface. It is shown that for big enough collision energies $E_{\mathrm{kin}}\ge 40$A GeV ($\sqrt{s}\ge 8$A GeV) the multipion system at a time moment $\tau$ ceases to be one connected unit but splits up into two separate spatial parts (drops), which move in opposite directions from one another with velocities which approach the speed of light with an increase of collision energy. This time $\tau$ is approximately invariant of the collision energy, and the corresponding $\tau =$ const. hypersurface can serve as a benchmark for the freeze-out time or the transition time from the hydrostage in hybrid models. The properties of this hypersurface are discussed.

We present a fully dynamical model to study nonequilibrium effects in both the chiral and the deconfinement phase transition. The sigma field and the Polyakov loop as the corresponding order parameters are propagated by Langevin equations of motion. The locally thermalized background is provided by a fluid of quarks and antiquarks. Allowing for an exchange of energy and momentum through dissipative and stochastic processes we ensure that the total energy of the coupled system remains conserved. We study its relaxational dynamics in different quench scenarios and are able to observe critical slowing down as well as the enhancement of long-wavelength modes at the critical point. During the fluid dynamical expansion of a hot plasma fireball typical nonequilibrium effects such as supercooling and domain formation occur when the system evolves through the first-order phase transition.

Background: Over the past 60 years, a large amount of experimental nuclear data have been obtained for reactions which probe the ${}^{16}$O compound nucleus near the $\alpha$ and proton separation energies, the energy regimes most important for nuclear astrophysics. Difficulties and inconsistencies in $R$-matrix fits of the individual reactions prompt a more complete analysis.

Purpose: Determine the level of consistency between the wide variety of experimental data using a multiple entrance/exit channel $R$-matrix framework. Using a consistent set of data from multiple reaction channels, attain an improved fitting for the ${}^{15}$N${(p,{\gamma }_0)}^{16}$O reaction data.

Methods: Reaction data for all available reaction channels were fit simultaneously using a multichannel $R$-matrix code.

Results: Over the wide range of experimental data considered, a high level of consistency was found, resulting in a single consistent $R$-matrix fit which described the broad level structure of ${}^{16}$O below $E_x=13.5$ MeV. The resulting fit was used to extract an improved determination of the low-energy $S$ factor for the reactions ${}^{15}$N${(p,\gamma )}^{16}$O and ${}^{15}$N${(p,\alpha )}^{12}$C.

Conclusion: The feasibility and advantages of a complete multiple entrance/exit channel $R$-matrix description for the broad level structure of ${}^{16}$O has been achieved. A future publication will investigate the possible effects of the multiple-channel analysis on the reaction ${}^{12}$C${(\alpha ,\gamma )}^{16}$O.

The ${}^{13}$C(${}^9$Be,${}^8$Li)${}^{14}$N angular distribution was measured with a ${}^9$Be beam of 40 MeV. The proton spectroscopic factor of the ${}^9$Be ground state was extracted to be 0.73 $\pm$ 0.15 by the normalization of the calculated differential cross sections with the distorted-wave Born approximation (DWBA) to the experimental data. The spectroscopic factor was compared to existing theoretical and experimental values.

We have calculated energies of the first two excited states of ${}^{19}$Mg by using a model that was previously successful for the ground state. Computed excitation energies are 1.12 and 1.54 MeV for (3/2${}^{-}$) and (5/2${}^{-}$), respectively—somewhat in disagreement with values of 1.38 and 2.14 MeV from a recent experiment.

We report microscopic calculations of the equation of state of symmetric nuclear matter and the nucleon-nucleus optical potential in the Brueckner-Hartree-Fock approach. The calculations use several internucleon ($NN$) potentials, such as the Hamada-Johnston, Urbana v14, Argonne v14, Argonne v18, Reid93, and Nijm II along with and without two types of three-body forces (TBFs): the Urbana IX model and the phenomenological density-dependent three-nucleon interaction model of Lagris and Pandharipande [Nucl. Phys. A 359, 349 (1981)] and Friedman and Pandharipande [Nucl. Phys. A 361, 502 (1981)]. The inclusion of TBFs helps to reproduce the saturation properties for symmetric nuclear matter rather well as expected. The proton-nucleus optical potential has been calculated by folding the calculated reaction matrices (with and without three-body forces) over the nucleon density distributions obtained from the relativistic mean-field theory. The results show that the inclusion of TBFs reduces the strength of the central part of the optical potential in the nuclear interior and affects the calculated spin-orbit potential only marginally. As a test of the calculated potential, we have analyzed proton differential elastic scattering, analyzing power, and spin-rotation data from ${}^{40}$Ca and ${}^{208}$Pb at 65 and 200 MeV. It is observed that the inclusion of TBFs improves the agreement with the experiment especially for the polarization data.

We have investigated the three-body force (TBF) effect on the neutron and proton momentum distributions in asymmetric nuclear matter within the framework of the extended Brueckner-Hartree-Fock approach by adopting the $AV18$ two-body interaction plus a microscopic TBF. In asymmetric nuclear matter, it is shown that the neutron and proton momentum distributions become different from their common distribution in symmetric nuclear matter. The predicted depletion of the proton hole states increases while the neutron one decreases as a function of isospin asymmetry. The TBF effect on the neutron and proton momentum distributions turns out to be negligibly weak at low densities around and below the normal nuclear density. The TBF effect is found to become sizable only at high densities well above the saturation density, and inclusion of the TBF leads to an overall enhancement of the depletion of the neutron and proton Fermi seas.

Background: Direct determination of the neutrino mass through double-$\beta$ decay is at the present time one of the most important areas of experimental and theoretical research in nuclear and particle physics.

Purpose: We calculate nuclear matrix elements for the extraction of the average neutrino mass in neutrinoless double-$\beta$ decay.

Methods: The microscopic interacting boson model (IBM-2) is used.

Results: Nuclear matrix elements in the closure approximation are calculated for ${}^{48}$Ca, ${}^{76}$Ge, ${}^{82}$Se, ${}^{96}$Zr, ${}^{100}$Mo, ${}^{110}$Pd, ${}^{116}$Cd, ${}^{124}$Sn, ${}^{128}$Te, ${}^{130}$Te, ${}^{148}$Nd, ${}^{150}$Nd, ${}^{154}$Sm, ${}^{160}$Gd, and ${}^{198}$Pt decay.

Conclusions: Realistic predictions for the expected half-lives in neutrinoless double-$\beta$ decay with light and heavy neutrino exchange in terms of neutrino masses are made and limits are set from current experiments.