A formalism based on the complex-scaling method is developed and applied to solve the four-nucleon scattering problem above the break-up threshold. Converged calculations are presented for the isospin $T=0$ and $T=1$ channels in several energy regions above both the three- and the four-particle break-up thresholds.

Background: There is a renewed experimental interest in antiproton-proton scattering with an intense, possibly polarized antiproton beam. On the theoretical side, significant progress has been made in the understanding of the nuclear force from chiral effective field theory.

Purpose: We provide a high-quality model-independent description of the available low-energy antiproton-proton scattering data.

Method: We perform a new energy-dependent partial-wave analysis of all antiproton-proton elastic ($\overline{p}p\to \overline{p}p$) and charge-exchange ($\overline{p}p\to \overline{n}n$) scattering data below 925 MeV/$c$ antiproton laboratory momentum. The Schrödinger equation is solved for the coupled $\overline{p}p$ and $\overline{n}n$ channels. The relevant long-range parts of the electromagnetic and the one- and two-pion exchange interactions are included exactly. The short-range interactions, including the coupling to the mesonic annihilation channels, are parametrized by a complex boundary condition at a radius of $r=1.2$ fm.

Results: The updated database, which includes significantly more high-quality charge-exchange data, contains 3749 scattering data. The fit gives ${\chi }_{\min }^2/N_{\mathrm{df}}=1.048$, where $N_{\mathrm{df}}=3578$ is the number of degrees of freedom. We discuss the description of the experimental data and we present the antiproton-proton phase-shift parameters.

Conclusions: Chiral effective field theory provides an excellent long-range antinucleon-nucleon interaction. The results of the PWA should serve as the starting point for future theoretical and experimental investigations of low-energy antiproton-proton scattering.

The $E1$ response in ${}^{208}$Pb is studied within a microscopic multiphonon approach which solves the nuclear eigenvalue problem in a basis of microscopic multiphonon states generated iteratively starting from the Tamm-Dancoff phonons. Attention is focused on the low-energy excitations below the giant dipole resonance peak.

The ${}^9$Be(${}^6\mathrm{Li},d)$${}^{13}$C${}^{*}$ reaction at a beam energy of 42 MeV has been investigated using a large-acceptance silicon-strip detector array and the high-resolution Q3D magnetic spectrograph. The Q3D facilitated the unambiguous determination of the reaction channel via identification of the deuteron ejectile, thereby providing the spectrum of excited states in ${}^{13}$C in the range from 10.7 to 15.0 MeV. The silicon array was used to detect and identify the ${}^{13}$C recoil-breakup products with efficiencies of up to $49\%$. The results obtained for the absolute partial branching ratios represent the first complete measurements for states in this energy region and allow the extraction of reduced widths. The quantities measured for ${\Gamma }_{n0}/{\Gamma }_{\mathrm{tot}}$ and ${\Gamma }_{n1}/{\Gamma }_{\mathrm{tot}}$ are $0.91\pm 0.11$ and $\le$0.13 (10.753 MeV), $0.51\pm 0.04$ and $0.51\pm 0.04$ (10.818 MeV), $0.68\pm 0.03$ and $0.42\pm 0.02$ (10.996 MeV), $0.49\pm 0.08$ and $0.71\pm 0.11$ (11.848 MeV), and $0.49\pm 0.08$ and $0.53\pm 0.08$ (12.130 MeV), respectively. For the two observed higher-lying energy levels, ${\Gamma }_{\alpha 0}/{\Gamma }_{\mathrm{tot}}$ and ${\Gamma }_{n1}/{\Gamma }_{\mathrm{tot}}$ have been measured as $0.54\pm 0.02$ and $0.45\pm 0.02$ (13.760 MeV) and $0.94\pm 0.03$ and $0.13\pm 0.02$ (14.582 MeV), respectively. The consequences for the proposed molecular structures in ${}^{13}$C are explored following the extraction of reduced widths.

Excited states in ${}^{16}$C were populated via the ${}^9$Be(${}^{17}$N,${}^{16}$C+$\gamma$)X one-proton knockout reaction. The lifetime of the 2${}_1^{+}$ state in ${}^{16}$C was measured using the recoil distance method. The extracted lifetime of ${\tau }_{2_1^{+}}=11.4_{-0.9}^{+0.8}\left(\text{stat}\right)\pm 0.7{\left({\text{syst}}_{B\rho }\right)}_{-1.5}^{+0.0}\left({\text{syst}}_{\text{feeding}}\right)$ ps yields a deduced $B(E2;2_1^{+}\to 0_1^{+})=4.{21}_{-0.26}^{+0.34}{\left(\text{stat}\right)}_{-0.24}^{+0.28}{\left({\text{syst}}_{B\rho }\right)}_{-0.00}^{+0.64}\left({\text{syst}}_{\text{feeding}}\right)e^2{\mathrm{fm}}^4$ value in good agreement with a previous measurement. The one-proton knockout cross section is used to extract the proton amplitude of the ${}^{16}$C 2${}_1^{+}$ state, which confirms the neutron dominant character of this state. Gamma-ray branching ratios between the 2${}_2^{+}$ state and the 2${}_1^{+}$ and ground states were also determined. The results are compared with $p-sd$ shell model and no-core shell model (with $NN$ and $NN+NNN$) calculations. The inclusion of three-body forces are essential in order for the no-core shell model calculations to reproduce the experimental findings on the $\gamma$-ray branching ratios.

Fusion excitation functions with high precision have been measured for the ${}^{16}$O+${}^{76}$Ge and ${}^{18}$O+${}^{74}$Ge systems at energies near and below the Coulomb barrier. The barrier distributions have been extracted from the corresponding excitation functions. The coupling effect of the positive $Q$-value neutron transfer channel in the heavy-ion fusion reaction was examined by a comparison of the two systems. The fusion excitation functions are well reproduced by coupled-channels calculations including the 2${}^{+}$ and 3${}^{-}$ vibrational states of the targets and the 2${}^{+}$ rotational state of ${}^{18}$O projectile. No obvious fusion enhancement due to the positive $Q$-value two-neutron transfer for the ${}^{18}$O+${}^{74}$Ge system is observed as compared with the reference system of ${}^{16}$O+${}^{76}$Ge. Analogous systems which are available in the literature are also discussed to realize the role of one- and/or two-neutron transfers with positive $Q$ values in the fusion process.

Light particle ($n$, $p$, and $\alpha$) evaporation spectra have been measured in coincidence with $\gamma$ rays of different multiplicities, emitted from ${}^{97}$Tc${}^{*}$ and ${}^{62}$Zn${}^{*}$ compound systems at the excitation energies $\sim 36$ MeV. Statistical model analysis of the experimental data have been carried out to extract the value of the inverse level density parameter ($k$) at different angular momentum regions, corresponding to different $\gamma$ multiplicity. A systematic trend of a decrease of inverse level density parameter with the increase in angular momentum has been observed from the study of all three evaporation spectra, for both systems. Simultaneous analysis of all (major) light particle spectra provide useful information to understand the angular momentum dependence of nuclear level density in a consistent manner.

We examine whether the breakdown in elliptic flow quark number scaling observed at the Relativistic Heavy Ion Collider (RHIC) energy scan is related to the turning off of deconfinement by testing the hypothesis that hydrodynamics and parton coalescence always apply, but are obscured, at lower energies, by variations in the widths of quark and antiquark rapidity distribution. We find that this effect is enough to spoil quark number scaling in elliptic flow. A lack of scaling in data, therefore, does not signal the absence of partonic degrees of freedom and hadronization by coalescence. In a coalescing partonic fluid, however, elliptic flow of antibaryons should be greater than that of baryons, since antibaryons contain a greater admixture of partons from the highly flowing midrapidity region. Intriguingly, purely hadronic dynamics has a similar dependence of baryon-antibaryons elliptic flow as purely partonic dynamics, again because antibaryons tend to come from regions where the deviation of the system from hydrodynamic behavior is at its smallest. The opposite trend observed in experiment is therefore an indication that we might be misunderstanding the origin of elliptic flow. We finish by discussing possible explanations of this and suggest experimental measurements capable of clarifying the situation.

The direct neutron capture reaction is investigated within the potential model. All allowed electric dipole ($E1$), electric quadrupole ($E2$), and magnetic dipole ($M1$) transitions are taken into account. The nuclear structure ingredients involved in the calculation are determined from experimental data whenever available, and if not, from global microscopic nuclear models. A special emphasis is put on the excitation spectrum deduced from a mean field plus combinatorial model of nuclear level densities. It is shown that considering either a total intrinsic nuclear level density or one-particle, one-hole neutron excitations give rise to similar predictions provided the corresponding average spectroscopic factor is renormalized. The potential model is shown to provide a fair agreement between the predicted radiative neutron capture cross section and experimental data for light targets as well as with previous calculations. A systematic study for about 6400 nuclei with $8\le Z\le 102$ lying between the proton and neutron drip lines shows that the direct capture cross sections (and consequently reaction rates of astrophysical interest) are proportional to the number of levels available below the neutron threshold and decreases with decreasing neutron separation energies. It is found that the $E2$ and $M1$ components are usually negligible with respect to the $E1$ contribution, but that they can dominate the direct capture rate for about several hundred nuclei.

The comparison of photoproduction cross sections for $c\overline{c}$ and $b\overline{b}$ in PbPb and $p$Pb collisions can show sensitivity to nuclear shadowing effects. The photoproduction of vector mesons is even more sensitive to the underlying gluon distributions. In this study we present the cross sections and rapidity dependence of the photoproduction of heavy quarks and the exclusive production of vector mesons in ultraperipheral $p$Pb and PbPb collisions at the CERN Large Hadron Collider at $\sqrt{s_{{}_{NN}}}=5$ TeV and $\sqrt{s_{{}_{NN}}}=2.76$ TeV, respectively. The potentials of using these processes for constraining nuclear gluon shadowing are explored. It is found that the photoproduction of $J/\psi$ and ${\rm Y}$ in PbPb collisions in particular exhibits very good sensitivity to gluon shadowing.

Excited states in ${}^{145}$Ba, populated in spontaneous fission of ${}^{248}$Cm, have been studied by means of $\gamma$ spectroscopy, using high-fold $\gamma$ coincidences measured with the EUROGAM2 array of Ge detectors. The 507.7-keV level, which has been assigned in this work spin and parity 9/2${}^{+}$, belongs to the $i_{13/2}$ intruder band. We have identified in ${}^{145}$Ba a new 9/2${}_2^{-}$ level at 346.3 keV and a band on top of it. The negative parity indicates that it is not due to an octupole excitation. The position of the 5/2${}^{-}$ ground state, relative to the positive-parity band, could be reproduced by calculations with a reflection-symmetric potential and we do not observe a parity doublet to the ground state. Therefore we conclude that octupole excitations in ${}^{145}$Ba are most likely due to octupole vibrations coupled either to the reflection-symmetric ground state or to the $i_{13/2}$, decoupled neutron configuration.

Large-scale shell model calculations based on a new diagonalization algorithm are performed in order to investigate the low-energy spectroscopic properties of a chain of Te isotopes going from ${}^{126}$Te to ${}^{132}$Te. The computed energy levels, $E2$ and $M1$ transition strengths are compared to experiments and put in relation to the scheme provided by the interacting boson model. The comparative analysis allows us to determine the proton-neutron symmetry as well as the bosonic content of the states.

The energy of actinide nuclei in the fusionlike deformation valley has been determined from a liquid-drop model, taking into account the proximity energy, the mass and charge asymmetries, and the shell and pairing energies. Double-humped potential barriers appear. The saddle point corresponds to the second maximum and to the transition from compact one-body shapes with a deep neck to two touching ellipsoids. The scission point, where the effects of the nuclear attractive forces between the fragments vanish, lies at the end of an energy plateau below the saddle point and corresponds to two well-separated fragments. The kinetic and excitation energies of the fragments come from the energy on this plateau. The shell and pairing effects play a main role to decide the most probable decay path. The heights of the potential barriers roughly agree with the experimental data and the calculated half-lives follow the trend of the experimental values. A shallow third minimum and a third peak appear in specific asymmetric exit channels where one fragment is close to a double magic quasispherical nucleus, while the other one evolves from oblate to prolate shapes.

The mass region with a proton number just below the magic number $Z=82$ is known to exhibit a rich variety of shape phenomena. Inspired by the recent extensive experimental measurements of the transition probabilities for the yrast bands in some Pt isotopes in this mass region, we have performed a detailed investigation of ${}^{180-190}$Pt using the triaxial projected shell model approach (TPSM). It is demonstrated that by performing the exact three-dimensional angular-momentum projection on multi-quasiparticle configurations, constructed from the traxially deformed mean field, the TPSM provides a consistent description of the yrast band structures, the $\gamma$-vibrational band, and the second $0^{+}$ band in these nuclei. Further, the observed rapid variations in the quadrupole transition probability along the yrast line of these isotopes are well reproduced in the present study.

We compare the predictions of different variants of chiral effective field theory for the $\gamma p$ elastic scattering differential cross section. We pay particular attention to the role of pion loops, and the impact that a heavy-baryon expansion has on the behavior of those loops. We also correct erroneous results for these loops that were published by Pascalutsa and Phillips [Phys. Rev. C 67, 055202 (2003)].

Pairing correlations have a strong influence on nuclear level densities. Empirical descriptions and theoretical models have been developed to take these effects into account. The present article discusses cases, where descriptions of nuclear level densities are inconsistent or in conflict with the present understanding of nuclear properties. Phenomenological approaches consider an energy-shift parameter. However, the absolute magnitude of the energy shift, which actually corresponds to the pairing condensation energy, is generally not compatible with the observation that stable pairing correlations are present in essentially all nuclei. It is also shown that in the BCS model pairing condensation energies and critical pairing energies are inconsistent for light nuclei. A modification to the composite Gilbert-Cameron level-density description is proposed, and the use of more realistic pairing theories is suggested.

We present a systematic configuration-interaction shell-model calculation on the structure of light tin isotopes with a global optimized effective interaction. The starting point of the calculation is the realistic CD-Bonn nucleon-nucleon potential. The unknown single-particle energies of the $1d_{3/2}$, $2s_{1/2}$, and $0h_{11/2}$ orbitals and the $T=1$ monopole interactions are determined by fitting to the binding energies of 157 low-lying yrast states in ${}^{102-132}$Sn. We apply the Hamiltonian to analyze the origin of the spin inversion between ${}^{101}$Sn and ${}^{103}$Sn that was observed recently and to explore the possible contribution from interaction terms beyond the normal pairing.

Proton-neutron, neutron-neutron, and proton-proton momentum-correlation functions ($C_{pn},C_{nn}$, and $C_{pp}$) are systematically investigated for ${}^{15}\mathrm{C}$ and other C-isotope-induced collisions at different entrance channel conditions within the framework of the isospin-dependent quantum-molecular-dynamics model complemented by the correlation after burner (crab) computation code. ${}^{15}\mathrm{C}$ is a prime exotic nucleus candidate due to the weakly bound valence neutron coupling with closed-neutron-shell nucleus ${}^{14}\mathrm{C}$. To study density dependence of the correlation function by removing the isospin effect, the initialized ${}^{15}\mathrm{C}$ projectiles are sampled from two kinds of density distribution from the relativistic mean-field (RMF) model in which the valence neutron of ${}^{15}\mathrm{C}$ is populated in both $1d5/2$ and $2s1/2$ states, respectively. The results show that the density distributions of the valence neutron significantly influence the nucleon-nucleon momentum-correlation function at large impact parameters and high incident energies. The extended density distribution of the valence neutron largely weakens the strength of the correlation function. The size of the emission source is extracted by fitting the correlation function by using the Gaussian source method. The emission source size as well as the size of the final-state phase space are larger for projectile samplings from more extended density distributions of the valence neutron, which corresponds to the $2s1/2$ state in the RMF model. Therefore, the nucleon-nucleon momentum-correlation function can be considered as a potentially valuable tool to diagnose exotic nuclear structures, such as the skin and halo.

We study the importance of the initial state, baryon stopping, and baryon number transport for the dynamical evolution of a strongly interacting system produced in heavy ion collisions. We employ a hybrid model, which combines the fluid dynamical evolution of the fireball with a transport treatment for the initial state and the final hadronic phase. We present results for collisions at beam energies from $\sqrt{s_{NN}}=7.7$ to 200 GeV. We study various observables such as the centrality dependent freeze-out parameters, the nonmonotonic behavior of effective slope parameter parameter with particle mass as well as the apparent difference in particle and antiparticle elliptic flow. Our results are in reasonable agreement with the available data. We find that the propagation of the baryon-number current in the hydrodynamic evolution as well as the transport treatment of the hadronic phase are essential for reproducing the experimental data.

We show that the effect of finite acceptance drastically influences the net-baryon and net-charge cumulants, which are believed to be sensitive probes of the QCD phase diagram. We derive general formulas that relate the true cumulants $K_n$ which reflect the full dynamics of the system with the actually measured cumulants $c_n$ for a given acceptance, modeled by a binomial probability parameter $p$. We find that this relation involves additional moments which cannot be expressed by cumulants and should be measured in order to extract any potential information about the QCD critical point. We demonstrate that for a wide range of the true cumulant ratios $K_n/K_m$ the measured ratios $c_n/c_m$ quickly converge if $p<1/2$, which makes the interpretation of the data very challenging, especially in case of the net-proton cumulants. Our study further suggests that the measurement of net-charge cumulants may be more advantageous for the investigation of the QCD phase diagram.