We apply a spin-projection method to calculate microscopically the level densities of a family of nickel isotopes ${}^{59-64}$Ni using the shell model Monte Carlo approach in the complete $pf{g}_{9/2}$ shell. Accurate ground-state energies of the odd-mass nickel isotopes, required for the determination of excitation energies, are determined using the Green's function method recently introduced to circumvent the odd particle-number sign problem. Our results are in excellent agreement with recent measurements based on proton evaporation spectra and with level counting data at low excitation energies. We also compare our results with neutron resonance data, assuming equilibration of parity and a spin-cutoff model for the spin distribution at the neutron binding energy, and find good agreement with the exception of ${}^{63}$Ni.

The linear term proportional to $|N-Z|$ in the nuclear symmetry energy (Wigner energy) is obtained in a model that uses isovector pairing on single-particle levels from a deformed potential combined with a ${\vec{T}}^2$ interaction. The pairing correlations are calculated by numerical diagonalization of the pairing Hamiltonian acting on the six or seven levels nearest the $N=Z$ Fermi surface. The experimental binding energies of nuclei with $N\approx Z$ are well reproduced. The Wigner energy emerges as a consequence of restoring isospin symmetry. We have found the Wigner energy to be insensitive to the presence of moderate isoscalar pair correlations.

First-order phase transitions (PTs) with more than one globally conserved charge, so-called noncongruent PTs, have characteristic differences compared to congruent PTs (e.g., dimensionality of phase diagrams and location and properties of critical points and end points). In the present article we investigate the noncongruence of the nuclear liquid-gas PT at subsaturation densities and the deconfinement PT at high densities and/or temperatures in Coulombless models, relevant for heavy-ion collisions and neutron stars. For the first PT, we use the FSUgold relativistic mean-field model and for the second one the relativistic chiral SU(3) model. The chiral SU(3) model is one of the few models for the deconfinement PT, which contains quarks and hadrons in arbitrary proportions (i.e., a “solution”) and gives a continuous transition from pure hadronic to pure quark matter above a critical point. The study shows the universality of the applied concept of noncongruence for the two PTs with an upper critical point and illustrates the different typical scales involved. In addition, we find a principle difference between the liquid-gas and the deconfinement PTs: in contrast to the ordinary Van-der-Waals-like PT, the phase coexistence line of the deconfinement PT has a negative slope in the pressure-temperature plane. As another qualitative difference we find that the noncongruent features of the deconfinement PT become vanishingly small around the critical point.

The performance of the Bayesian unfolding method in extracting the event-by-event (EbyE) distributions of harmonic flow coefficients $v_n$ is investigated using a toy model simulation, as well as simulations based on the HIJING model and a multiphase transport (AMPT) model. The unfolding method is shown to recover the input $v_2$–$v_4$ distributions for events with multiplicities similar to those observed in $\mathrm{Pb}+\mathrm{Pb}$ collisions at the Large Hadron Collider. The effects of the nonflow are evaluated using the HIJING simulation with and without a flow afterburner. The probability distribution of $v_n$ from nonflow is nearly a Gaussian and can be largely suppressed with the data-driven unfolding method used by the ATLAS Collaboration. The residual nonflow effects have no appreciable impact on the $v_3$ distributions, but affect the tails of the $v_2$ and $v_4$ distributions; these effects manifest as a small simultaneous change in the mean and standard deviation of the $v_n$ distributions. For the AMPT model, which contains both flow fluctuations and nonflow effects, the reduced shape of the extracted $v_n$ distributions is found to be independent of $p_{\mathrm{T}}$ in the low-$p_{\mathrm{T}}$ region, similar to what is observed in the ATLAS data. The prospect of using the EbyE distribution of the harmonic spectrum aided by the unfolding technique as a general tool to study azimuthal correlations in high-energy collisions is also discussed.

We have calculated the properties of nuclear matter in a self-consistent manner with a quark-meson coupling mechanism incorporating the structure of nucleons in vacuum through a relativistic potential model; where the dominant confining interaction for the free independent quarks inside a nucleon is represented by a phenomenologically average potential in equally mixed scalar-vector harmonic form. Corrections due to spurious center of mass motion as well as those due to other residual interactions, such as the one gluon exchange at short distances and quark-pion coupling arising out of chiral symmetry restoration, have been considered in a perturbative manner to obtain the nucleon mass in vacuum. The nucleon-nucleon interaction in nuclear matter is then realized by introducing additional quark couplings to $\sigma$ and $\omega$ mesons through mean field approximations. The relevant parameters of the interaction are obtained self-consistently while realizing the saturation properties such as the binding energy, pressure, and compressibility of the nuclear matter. We also discuss some implications of chiral symmetry in nuclear matter along with the nucleon and nuclear $\sigma$ term and the sensitivity of nuclear matter binding energy with variations in the light quark mass.

We demonstrate that when two colliding nuclei approach each other, their quantum vibrations are damped near the touching point. We show that this damping is responsible for the fusion hindrance phenomena measured in the deep sub-barrier fusion reactions. To show those, we, for the first time, apply the random-phase-approximation method to the two-body ${}^{16}\mathrm{O}+{}^{16}\mathrm{O}$ and ${}^{40}\mathrm{Ca}+{}^{40}\mathrm{Ca}$ systems. We calculate the octupole transition strengths for the two nuclei that adiabatically approach each other. The calculated transition strength drastically decreases near the touching point, which strongly suggests the vanishing of the quantum couplings between the relative motion and the vibrational intrinsic degrees of freedom of each nucleus. Based on this picture, we also calculate the fusion cross section for the ${}^{40}\mathrm{Ca}+{}^{40}\mathrm{Ca}$ system by using the coupled-channel method with a damping factor that simulates the vanishing of the couplings. The calculated results reproduce the experimental data well, which indicates that the smooth transition from the sudden to the adiabatic processes indeed occurs in the deep sub-barrier fusion reactions.

An exclusive measurement of the $dd{\to }^3\mathrm{He}n{\pi }^0$ reaction was carried out at a beam momentum of $p_d=$ 1.2 GeV/$c$ using the WASA-at-COSY facility. Information on the total cross section as well as differential distributions was obtained. The data are described by a phenomenological approach based on a combination of a quasifree model and a partial wave expansion for the three-body reaction. The total cross section is found to be ${\sigma }_{\mathrm{tot}}=(2.89\pm 0.{01}_{\mathrm{stat}}\pm 0.{06}_{\mathrm{sys}}\pm 0.{29}_{\mathrm{norm}})\mu \mathrm{b}$. The contribution of the quasifree processes (with the beam or target neutron being a spectator) accounts for 38$\%$ of the total cross section and dominates the differential distributions in specific regions of phase space. The remaining part of the cross section can be described by a partial wave decomposition indicating the significance of $p$-wave contributions in the final state.

The $\beta$ decay of five heavy, neutron-rich nuclei, ${}^{203,204}$Pt and ${}^{200-202}$Ir, has been investigated following relativistic cold fragmentation reactions of lead projectiles using the FRS+RISING setup at GSI. This paper reports on the study of the low-lying states in the decay daughter nuclei ${}^{203,204}$Au and ${}^{200-202}$Pt. The characteristic $\gamma$ rays for each nucleus have been determined using $\beta$-delayed $\gamma$-ray spectroscopy. Tentative level schemes, relative intensities, and apparent $\beta$ feedings are provided. These data are compared with shell-model calculations, which indicate a substantial contribution to the total $\beta$ strength from high-energy first-forbidden $\beta$-decay transitions in this mass region.

The cranked relativistic Hartree-Bogoliubov theory has been applied for a systematic study of pairing and rotational properties of actinides and light superheavy nuclei. Pairing correlations are taken into account by the Brink-Booker part of finite-range Gogny D1S force. For the first time, in the covariant density functional theory (CDFT) framework, the pairing properties of deformed nuclei are studied via the quantities (such as three-point ${\Delta }^{\left(3\right)}$ indicators) related to odd-even mass staggerings. The investigation of the moments of inertia at low spin and the ${\Delta }^{\left(3\right)}$ indicators shows the need for an attenuation of the strength of the Brink-Booker part of the Gogny D1S force in pairing channel. The investigation of rotational properties of even-even and odd-mass nuclei at normal deformation, performed in the density functional theory framework in such a systematic way for the first time, reveals that in the majority of the cases the experimental data are well described. These include the evolution of the moments of inertia with spin, band crossings in the $A\ge 242$ nuclei, the impact of the particle in specific orbital on the moments of inertia in odd-mass nuclei. The analysis of the discrepancies between theory and experiment in the band crossing region of $A\le 240$ nuclei suggests the stabilization of octupole deformation at high spin, not included in the present calculations. The evolution of pairing with deformation, which is important for the fission barriers, has been investigated via the analysis of the moments of inertia in the superdeformed minimum. The dependence of the results on the CDFT parametrization has been studied by comparing the results of the calculations obtained with the NL1 and NL3* parametrizations.

We report an investigation of the structure of the ${}^{12}$C nucleus employing a newly developed configuration-mixing method. In the three-dimensional coordinate-space representation, we generate a number of Slater determinants with various correlated structures using the imaginary-time algorithm. We then diagonalize a many-body Hamiltonian with the Skyrme interaction in the space spanned by the Slater determinants with parity and angular momentum projections. Our calculation reasonably describes the ground and excited states of the ${}^{12}$C nucleus, both for shell-model-like and cluster-like states. The excitation energies and transition strengths of the ground-state rotational band are well reproduced. Negative-parity excited states, $1_1^{-}$, $2_1^{-}$, and $3_1^{-}$, are also reasonably described. The second and third $0^{+}$ states, $0_2^{+}$ and $0_3^{+}$, appear at around 8.8 and 15 MeV, respectively. The $0_2^{+}$ state shows a structure consistent with former results of the $\alpha$-cluster models. However, the calculated radius of the $0_2^{+}$ state is smaller than in those calculations. The three-$\alpha$ linear-chain configuration dominates in the $0_3^{+}$ state.

The nuclear suppression factor $R_{AA}$ of single inclusive hadrons measured in ultrarelativistic heavy-ion collisions was the first observable to study jet quenching, i.e., the final state interaction of hard parton showers with the surrounding bulk matter. While its transverse momentum ($P_T$) dependence of $R_{AA}$ observed at RHIC was weak and hence never decisive in constraining models, there is now a strong and nontrivial $P_T$ dependence observed at the LHC. This has been a challenge for several models which worked well at RHIC kinematics. However, in more general terms it is also of importance to understand what physical properties of the hard process and the parton-medium interaction are reflected in $R_{AA}\left(P_T\right)$. The results of the work presented here suggest that the two main effects underlying the $P_T$ dependence are the Quantum-Chromodynamics scale evolution of the fragmentation function and the limited distance (set by the typical medium length scale) for which a shower evolves in the medium.

Elastic scattering data for ${}^{11}$Li, ${}^6$Li, and ${}^6$He $+$ ${}^{208}$Pb at incident energies of 29.8 MeV, 29 MeV, and 18 MeV, respectively, were analyzed by means of coupled discretized continuum channels (CDCC) calculations. Dynamic polarization potentials (DPPs) of the trivially equivalent local potential (TELP) type were derived from these calculations and compared. The dipole polarizability factor $\alpha$ for ${}^{11}$Li obtained by fitting a Coulomb polarization potential to the long-range part of the real DPP is consistent with the theoretical value of $5.7$ fm${}^3$. These results point to the dineutron model providing a very good description of ${}^{11}$Li breakup coupling effects. The much larger Coulomb dipole polarizability of ${}^{11}$Li suggests the persistence of large deviations from Rutherford scattering at sub-barrier energies for medium mass targets, a prediction confirmed by CDCC calculations.

The nuclear level densities, spin cut off parameters, and entropies have been extracted in ${}^{116-119}$Sn and ${}^{162,163}$Dy nuclei using superconducting theory, which includes nuclear pairing interaction. The results agree well with the recent data obtained from experimental level densities by the Oslo group for these nuclei. Also, the entropy excess ratio proposed by Razavi et al. [R. Razavi, A.N. Behkami, S. Mohammadi, and M. Gholami, Phys. Rev. C 86, 047303 (2012)] for a proton and neutron as a function of nuclear temperature have been evaluated and are compared with the spin cut off excess ratio. The role of the neutron (proton) system is well determined by the entropy excess ratio as well as the spin cut off excess ratio. The moment of inertia for even-odd and even-even nuclei are also compared. The moment of inertia carried by a single hole is smaller than the single particle moment of inertia.

Based on recent experimental data, the band structure of the odd-odd nucleus ${}^{86}$Y has been studied. The positive-parity yrast band built on the configuration $\pi g_{9/2}\otimes \nu g_{9/2}^{-1}$ shows a large signature splitting, and a signature inversion occurs at $I\sim 13\hslash$. The signature inversion is interpreted by the competition between single-particle and collective excitations in this nucleus. The negative-parity dipole band, which is probably connected with magnetic rotation, is assigned to the configurations $\pi g_{9/2}^2{(p_{3/2}/f_{5/2})}^{-1}\otimes \nu g_{9/2}^{-1}$ before and to $\pi g_{9/2}^2{(p_{3/2}/f_{5/2})}^{-1}\otimes \nu g_{9/2}^{-3}$ after the alignment. Self-consistent titled axis cranking calculations based on relativistic mean-field theory are performed to interpret the rotational structure. Characteristic features of magnetic rotation are found for the negative-parity band.

Excited states in ${}^{162}$Yb were populated via ${\beta }^{+}$/EC decay and were studied via conversion electrons and γ-ray spectroscopy at the Tandem Accelerator in the INFN Laboratory Nazionali del Sud in Catania, Italy. Conversion electrons were detected by a miniorange spectrometer with a transmission energy window that ranged from 500 to 1300 keV. The $E$0 decay of the first excited state at 1006 keV to the ground state was observed, and a $X$($E$0/$E$2) value was deduced. The value is compared to a few IBM-1 calculations by using the ECQF formalism or the full Hamiltonian in multipole expansion. Calculations turn out to be quite sensitive to properties related to nuclear shape.

Background: The temperature in heavy-ion collisions is an important question because it reflects the violence of the collisions and affects the results of many important parameters in nuclear physics.

Purpose: In this work, we focus on the investigation of the temperature of the measured fragments in the 1$A$ GeV ${}^{112,124}$Sn+${}^{112,124}$Sn, and ${}^{124,36}$Xe+Pb reactions.

Methods: The isobaric yield ratio method is deduced in a grand-canonical theory. The decay contribution and the pairing energy contribution to the free energy of the fragment are considered in the analysis.

Results: For the odd $I$ ($I\equiv N-Z$) fragment the decay or pairing energy contribution is found unnecessary. For the even $I$ fragments, both the decay contribution and the decay plus pairing energy contribution can weaken the staggering in the isobaric yield ratios. For the odd $I$ fragment, the temperature in this work is consistent with that of the modified Fisher model [Phys. Rev. C 86, 054611 (2012)]. For the even $I$ fragment, the temperature at which the decay plus the pairing energy contribution have been taken in account is consistent with that of the the odd $I$ fragments. The isospin dependence of the temperature determined by the isobaric yield ratio method is also found.

Conclusions: In the grand-canonical theory, after the correction of the decay plus pairing energy to the free energy of the fragments, reasonable temperature of the even $I$ fragment can be obtained.

Background: The recoil-corrected continuum shell model provides coupled-channels solutions for bound and unbound wave functions from realistic effective interactions. The wave functions are antisymmetric and contain no spurious components because the calculations are performed in the center-of-mass system.

Purpose: This model has now been extended to include 1$\hslash \omega$ excitations in the structure of $p$-shell target (residual) nuclei, hence allowing 0$s$-shell knockout processes. Several reactions involving the ${}^{12}$C compound system are investigated to demonstrate the utility of the model.

Methods: The states of ${}^{11}$B and ${}^{11}$C are constructed in the nonspurious 0$\hslash \omega$ plus 1$\hslash \omega$ model space. An interaction, fitted to Cohen and Kurath (8-16) plus Reid soft core $g$-matrix elements, is employed. One nucleon is coupled to these states to create a basis for the bound and scattering states for ${}^{12}$C.

Results: Calculated elastic and inelastic cross sections agree well with available data. The calculated transverse response at high momentum transfer is lower than that extracted from data. Although significant, meson exchange currents are not sufficient to give agreement with data. Likewise inclusion of 0$s$-shell knockout is not sufficient to provide agreement. The high-energy octupole resonance appears at low momentum transfer and an energy of 106/$A^{1/3}$.

Conclusions: The model should provide meaningful predictions for states near the proton drip line via the ($p$,$n$) reaction. Coupled-channels solutions are necessary for describing ${}^{12}$C($e$,$e^{\prime }x$) at low momentum transfer. Lack of strength at low energy and momentum transfer in optical model calculations of ${}^{12}$C($e$,$e^{\prime }x$) is at least partly attributable to the omission of giant resonances. Data for (${\pi }^{+}$,${\pi }^{+\prime }p$)/(${\pi }^{-}$,${\pi }^{-\prime }p$) could verify this conclusion. Lack of strength in the transverse response may be attributable to recoil terms which are omitted in most calculations.

The generalized Fermi breakup model, recently demonstrated to be formally equivalent to the statistical multifragmentation model, if the contribution of excited states is included in the state densities of the former, is implemented. Because this treatment requires application of the statistical multifragmentation model repeatedly on hot fragments until they have decayed to their ground states, it becomes extremely computationally demanding, making its application to the systems of interest extremely difficult. Based on exact recursion formulas previously developed by Chase and Mekjian to calculate statistical weights very efficiently, we present an implementation which is efficient enough to allow it to be applied to large systems at high excitation energies. Comparison with the gemini$++$ sequential decay code and the Weisskopf-Ewing evaporation model shows that the predictions obtained with our treatment are fairly similar to those obtained with these more traditional models.

The scattering of proton-halo nucleus ${}^8$B from ${}^{208}$Pb at 170.3 MeV is shown to reveal a distinctive pattern in the change in $|S_L|$ that is induced by coupling to breakup channels. The same pattern had been found for ${}^8$B scattering from ${}^{58}$Ni at 30 MeV, an energy near the Coulomb barrier, and has been linked to various other respects in which scattering for this proton-halo nucleus differs from that of other light, weakly bound nuclei. The increase in $|S_L|$ for $L<80$, induced by breakup coupling, is associated with a substantial repulsive region in the dynamic polarization potential as determined by exact inversion. This repulsion appears to reduce the penetration of the projectile into the absorptive region of the interaction. This accounts for the fact that the increase in the total reaction cross section, due to breakup, is much less than the breakup cross section, and is consistent with the relatively small effect of breakup on the elastic scattering angular distribution compared with the large breakup cross section.