Cross sections for ${}^6\mathrm{Li}(\gamma ,\gamma ){}^6\mathrm{Li}$ have been measured at the High Intensity Gamma-Ray Source $\mathrm{(HI}\vec{\gamma }\mathrm{S)}$ and the sensitivity of these cross sections to the nucleon isoscalar polarizabilities was studied. Data were collected using a quasimonoenergetic 86-MeV photon beam at photon scattering angles of ${40}^{\circ }–{160}^{\circ }$. These results are an extension of a previous measurement at a lower energy. The earlier work indicated that the ${}^6\mathrm{Li}(\gamma ,\gamma ){}^6\mathrm{Li}$ reaction at 60 MeV provides a means of extracting the nucleon polarizabilities; this work demonstrates that the sensitivity of the cross section to the polarizabilities is increased at 86 MeV. A full theoretical treatment is needed to verify this conclusion and produce values of the polarizabilities.

The nucleon separation energies and shell gaps in nuclei over the whole nuclear chart are systematically studied with eight global nuclear mass models. For unmeasured neutron-rich and superheavy regions, the uncertainty of the predictions from these different mass models is still large. The latest version (WS4) of the Weizsäcker-Skyrme mass formula, in which the isospin dependence of model parameters is introduced into the macroscopic-microscopic approach inspired by the Skyrme energy-density functional, is found to be the most accurate one in the descriptions of nuclear masses, separation energies, and shell gaps. Based on the predicted shell gaps in nuclei, the possible magic numbers in superheavy nuclei region are investigated. In addition to the shell closures at $N=184,Z=114$, the subshell closures at around $N=178,Z=120$ could also play a role for the stability of superheavy nuclei.

We report quantum Monte Carlo calculations of electromagnetic transitions in ${}^8\mathrm{Be}$. The realistic Argonne $v_{18}$ two-nucleon and Illinois-7 three-nucleon potentials are used to generate the ground state and nine excited states, with energies that are in excellent agreement with experiment. A dozen $M1$ and eight $E2$ transition matrix elements between these states are then evaluated. The $E2$ matrix elements are computed only in impulse approximation, with those transitions from broad resonant states requiring special treatment. The $M1$ matrix elements include two-body meson-exchange currents derived from chiral effective field theory, which typically contribute 20%–30% of the total expectation value. Many of the transitions are between isospin-mixed states; the calculations are performed for isospin-pure states and then combined with empirical mixing coefficients to compare to experiment. Alternate mixings are also explored. In general, we find that transitions between states that have the same dominant spatial symmetry are in reasonable agreement with experiments, but transitions between different spatial symmetries are often underpredicted.

We propose a new approach for the treatment of isovector pairing in self-consistent mean field calculations which conserves exactly the isospin and the particle number in the pairing channel. The mean field is generated by a Skyrme–Hartree-Fock functional while the isovector pairing correlations are described in terms of quartets formed by two neutrons and two protons coupled to the total isospin $T=0$. In this framework we analyze the contribution of isovector pairing to the symmetry and Wigner energies. It is shown that the isovector pairing provides a good description of the Wigner energy, which is not the case for the mean field calculations in which pairing is treated by BCS-like models.

One theoretical method for studying nuclear scattering and resonances is via the multichannel algebraic scattering (MCAS) formalism. Studies to date with this method have used a simple collective-rotor prescription to model target states with which a nucleon couples. While generally these target states all belong to the same rotational band, for certain systems it is necessary to include coupling to states outside of that main band. Here, we extend MCAS to allow coupling of different strengths between such states and the rotor band. This is an essential consideration in studying the example examined herein, the scattering of neutrons from ${}^{22}\mathrm{Ne}$.

Azimuthal emission patterns of $K^{\pm }$ mesons have been measured in Ni + Ni collisions with the FOPI spectrometer at a beam kinetic energy of 1.91 A GeV. The transverse momentum $p_T$ integrated directed and elliptic flow of $K^{+}$ and $K^{-}$ mesons as well as the centrality dependence of $p_T$ - differential directed flow of $K^{+}$ mesons are compared to the predictions of hadron string dynamics and isospin quantum molecular dynamics transport models. The data exhibits different propagation patterns of $K^{+}$ and $K^{-}$ mesons in the compressed and heated nuclear medium and favor the existence of a kaon-nucleon in-medium potential, repulsive for $K^{+}$ mesons and attractive for $K^{-}$ mesons.

High-spin dipole structures in ${}^{143}\mathrm{Eu}$ have been studied via the fusion-evaporation ${}^{116}\mathrm{Cd}$ $({}^{31}\mathrm{P}$, $4n)$ reaction at a beam energy of 148 MeV using a clover detector array (Indian National Gamma Array). The parity of the two observed dipole bands has been firmly established from linear polarization measurements. Level lifetimes of these bands have been measured using the Doppler shift attenuation method. The drop in $B\left(M1\right)$ values with spin exhibits a clear signature of the magnetic rotational character of these two bands. Configurations were assigned to the bands in the framework of the shears mechanism with the principal axis cranking model calculation. Alignment of an additional proton in the $h_{11/2}$ orbital gives rise to the unique observation of a large increase in the $B\left(M1\right)$ values for the higher-lying band.

Three consecutive Coulomb excitation experiments were performed to measure the reduced transition probabilities in ${}^{120,122,124}\mathrm{Te}$ by using a ${}^{58}\mathrm{Ni}$ beam. For ${}^{120}\mathrm{Te}$ the collectivity was remeasured with high precision yielding a $B(E2;0_{\text{g.s.}}^{+}\to 2_1^{+})$ value of 0.666 (20) $\mathrm{e}{}^2\mathrm{b}{}^2$. From the $B\left(E2\right)$ values connecting higher-lying states, the nuclear structure of ${}^{120,122,124}\mathrm{Te}$ was determined and shows a rotational behavior quite in contrast with the vibrational structure of the level schemes. The data are compared with different models.

The total fusion (TF) excitation function for a ${}^6\mathrm{Li}$ projectile with a ${}^{64}\mathrm{Ni}$ target has been measured using the online characteristic $\gamma$ ray detection method at energies around the Coulomb barrier. The complete fusion (CF) excitation function for the system is subsequently estimated from the dominating neutron evaporation channels with the help of statistical model predictions. The CF cross sections exhibit a suppression of about $13\%$ compared to the one-dimensional barrier penetration model (1DBPM) at above-barrier energies, but no suppression is observed for TF cross sections. The observation does corroborate the estimated suppression for ${}^6\mathrm{Li}$ on ${}^{59}\mathrm{Co}$ target, but does not corroborate the recently proposed universal suppression factor for the ${}^6\mathrm{Li}$ projectile. The result supports the conjecture of reduced suppression of CF cross sections with decreasing target mass. At energies below the barrier, both the TF and the CF cross sections are enhanced. The observed enhancement of the CF process can be explained by channel coupling (CC), but the enhancement in TF cross sections is significantly higher than the CC predictions.

The presence of large event-by-event flow fluctuations in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) provides an opportunity to study a broad class of flow observables. This paper explores the correlations among harmonic flow coefficients $v_n$ and their phases ${\Phi }_n$, as well as the rapidity fluctuation of $v_n$. The study is carried out using the Pb + Pb events generated by the multiphase transport (AMPT) model with fixed impact parameter. The overall ellipticity or triangularity of events is varied by selecting on the eccentricities ${\epsilon }_n$ or the magnitudes of the flow vector $q_n$ in a subevent for $n=2$ and 3, respectively. The responses of the harmonic coefficients, the event-plane correlations, and the rapidity fluctuations to the change in ${\epsilon }_n$ and $q_n$ are then systematized. Strong positive correlations are observed among all even harmonics $v_2$, $v_4$, and $v_6$ (all increase with $q_2$), between $v_2$ and $v_5$ (both increase with $q_2$), and between $v_3$ and $v_5$ (both increase with $q_3$), consistent with the effects of nonlinear collective response. In contrast, an anticorrelation is observed between $v_2$ and $v_3$ similar to that seen between ${\epsilon }_2$ and ${\epsilon }_3$. These correlation patterns are found to be independent of whether selecting on $q_n$ or ${\epsilon }_n$, validating the ability of $q_n$ in selecting the initial geometry. A forward/backward asymmetry of $v_n\left(\eta \right)$ is observed for events selected on $q_n$ but not on ${\epsilon }_n$, reflecting dynamical fluctuations exposed by the $q_n$ selection. Many event-plane correlators show good agreement between $q_n$ and ${\epsilon }_n$ selections, suggesting that their variations with $q_n$ are controlled by the change of ${\epsilon }_n$ in the initial geometry. Hence these correlators may serve as promising observables for disentangling the fluctuations generated in various stages of the evolution of the matter created in heavy ion collisions.

We discuss the energy of the excited $2{}^{+}$ state in the unbound nucleus ${}^{26}\mathrm{O}$ using the three-body model of ${}^{24}\mathrm{O}+n+n$. This model fully takes into account the continuum effects, as well as the dineutron correlation of the valence neutrons. The present calculation yields the energy of 1.354 MeV, which is slightly smaller than the unperturbed energy, 1.54 MeV. The energy shifts for the ground and the $2{}^{+}$ states with respect to the unperturbed energy suggest that $0{}^{+}$ and the $2{}^{+}$ states in ${}^{26}\mathrm{O}$ show a typical spectrum well described by a short-range pairing interaction acting on two valence nucleons in the same orbit.

The isobaric analog state (IAS) in ${}^8\mathrm{B}$ is confirmed to decay by two-proton emission to the isobaric analog state in ${}^6\mathrm{Li}$, which emits a 3.563 MeV $\gamma$ ray. Upper limits on the yield to isospin breaking decay channels are also reported. The three-body correlations from the two-proton decay from ${}^8\mathrm{B}{}_{\text{IAS}}$ to ${}^6\mathrm{Li}{}_{\text{IAS}}$ are statistically different than the two-proton decay of its isospin partner, ${}^8\mathrm{C}{}_{\text{g.s.}}$.

High spin states in the ${}^{85}\mathrm{Sr}$ nucleus were populated in the reaction ${}^{76}\mathrm{Ge}({}^{13}\text{C},4n)$ at a beam energy of 45 MeV. The $\gamma -\gamma$ and $\gamma -\gamma -\gamma$ coincidence measurements have been utilized to establish the level scheme of ${}^{85}\mathrm{Sr}$ up to $I^{\pi }=35/2^{-}$. Nearly 50 new $\gamma$ rays and about 25 new levels were identified and most of the previously known levels confirmed. The spin-parity assignment of the levels was made by using the directional correlations of the oriented nuclei ratios and polarization asymmetry measurements. The shell-model calculations have been performed by using two recent interactions, JUN45 and jj44b, for a detailed comparison between theoretical results and the experimental data obtained in the present work. The shell-model results are in good agreements with the experimental data and are able to explain the various features such as the odd-even staggering well. Tilted axis cranking calculations were also performed to understand the magnetic rotation (MR) phenomenon at higher spins. One of the positive-parity $\Delta I=1$ bands has been assigned a three-quasiparticle (3qp) configuration, which appears to behave like a MR band. A negative-parity band populated up to $I^{\pi }=35/2^{-}$ was also assigned a 3qp configuration at low spin and a five-quasiparticle configuration at high spin; however, it does not exhibit the expected MR features, in contrast to a similar band in the ${}^{83}\mathrm{Kr}$ nucleus.

Using multidimensional Langevin equations, we have calculated the angular distribution of fission fragments with nonconstant values for the dissipation coefficient of the $K$ coordinate (the projection of the total angular momentum $I$ onto the symmetry axis of the fissioning nuclear system) for symmetry and asymmetry fission. We investigated the relaxation time of the $K$ coordinate, ${\tau }_K$, as a function of scission criteria and the asymmetry parameter. Calculations are done for ${}^{16}\mathrm{O}+{}^{232}\mathrm{Th}\to {}^{248}\mathrm{Cf}$, ${}^{16}\mathrm{O}+{}^{238}\mathrm{U}\to {}^{254}\mathrm{Fm}$, and ${}^{16}\mathrm{O}+{}^{248}\mathrm{Cm}\to {}^{264}\mathrm{Rf}$ reactions and obtained results are compared with available experimental data. Our calculations with nonconstant values of the $K$ coordinate show that the agreement between theoretical calculations and experimental data for asymmetry fission is better than that for symmetry fission.

Measurements of event-ensemble mean transverse momentum $\langle p_t\rangle$ vs charged-hadron multiplicity $n_{\text{ch}}$ for $p_t$ spectra from 5-TeV $p$-Pb and 2.76-TeV Pb-Pb collisions and from $p\text{−}p$ collisions for several energies have been reported recently. While in all cases $\langle p_t\rangle$ increases monotonically with $n_{\mathrm{ch}}$ the rate of increase is very different from system to system. Comparisons with several theory Monte Carlos reveal substantial disagreements and lead to considerable uncertainty on how to interpret the $\langle p_t\rangle$ data. In the present study we develop a two-component ($\mathrm{soft}+\mathrm{hard})$ model (TCM) of $p_t$ production in high energy nuclear collisions and apply it to the $\langle p_t\rangle$ data. The soft component is assumed to be a universal feature of high energy collisions independent of the A-B system or energy. The hard-component model is based on the observation that dijet production in $p-p$ collisions does not satisfy the eikonal approximation but does so in $A\text{−}A$ collisions. Hard-component properties are determined from previous measurements of hadron spectrum hard components, jet spectra, and fragmentation functions. The TCM describes the $p-p$ and Pb-Pb $\langle p_t\rangle$ data accurately, within data uncertainties, and the $p$-Pb data appear to transition smoothly from $p-p$ to $A\text{−}A$ $n_{\mathrm{ch}}$ trends.

We consider radiative corrections to polarization observables in elastic electron-proton scattering, in particular, for the polarization transfer measurements of the proton form factor ratio $\mu G_E/G_M$. The corrections are of two types: two-photon exchange (TPE) and bremsstrahlung (BS); in the present work we pay special attention to the latter. Assuming small missing energy or missing mass cutoff, the correction can be represented in a model-independent form, with both electron and proton radiation taken into account. Numerical calculations show that the contribution of the proton radiation is not negligible. Overall, at high $Q^2$ and energies, the total correction to $\mu G_E/G_M$ grows, but is dominated by TPE. At low energies both TPE and BS may be significant; the latter amounts to $\sim 0.01$ for some reasonable cut-off choices.