The Serber force has relative orbital parity symmetry and requires vanishing $\mathit{NN}$ interactions in partial waves with odd angular momentum. We illustrate how this property is well fulfilled for spin triplet states with odd angular momentum and violated for odd singlet states for realistic potentials but fails for chiral potentials. The analysis is carried out in terms of partial wave sum rules for $\mathit{NN}$ phase shifts, $r$-space potentials at long distances, and $V_{\mathrm{low}\hspace{0.5em}k}$ potentials. We analyze how Serber symmetry can be accommodated within a large-$N_c$ perspective when interpreted as a long-distance symmetry. A prerequisite for this is the numerical similarity of the scalar and vector meson resonance masses. The conditions under which the resonance exchange potential can be approximated by a Yukawa form are also discussed. Although these masses arise as poles on the second Riemann in $\pi \pi$ scattering, we find that within the large-$N_c$ expansion the corresponding Yukawa masses correspond instead to a well-defined large-$N_c$ approximation to the pole that cannot be distinguished from their location as Breit-Wigner resonances.

The production of ${\Delta }^0(1232)\to p{\pi }^{-}$ resonance is studied in peripheral $\mathrm{C}+\mathrm{Ta}$ collisions at $4.2A$ GeV using the 2-m propane bubble chamber exposed at JINR Dubna Synchrophasotron. Using an invariant mass distribution of $p{\pi }^{-}$ pairs and additional kinematical constrains, the mass, width, and kinematical characteristics of ${\Delta }^0$ resonance are determined. The ratio of the number of pions originated from ${\Delta }^0$ resonance decay to the number of all pions (resonant and nonresonant) is estimated. The analogous ratio for protons is also determined.

The density dependence of nuclear symmetry energy is determined from a systematic study of the isospin dependent bulk properties of asymmetric nuclear matter using the isoscalar and isovector components of the density dependent M3Y interaction. The incompressibility $K_{\infty }$ for the symmetric nuclear matter, the isospin dependent part $K_{\mathrm{asy}}$ of the isobaric incompressibility, and the slope $L$ are all in excellent agreement with the constraints recently extracted from measured isotopic dependence of the giant monopole resonances in even-$A$ Sn isotopes, from the neutron skin thickness of nuclei, and from analyses of experimental data on isospin diffusion and isotopic scaling in intermediate energy heavy-ion collisions. This work provides a fundamental basis for the understanding of nuclear matter under extreme conditions and validates the important empirical constraints obtained from recent experimental data.

The odd mass nucleus ${}^{139}\mathrm{Pm}$ has been studied to high spins through the ${}^{116}\mathrm{Cd}({}^{27}\mathrm{Al},4n){}^{139}\mathrm{Pm}$ reaction at an incident beam energy of 120 MeV. The de-exciting $\gamma$-rays were detected using an array of 12 Compton suppressed Ge detectors. A total of 46 new levels have been proposed in the present work as a result of the observation of 60 new $\gamma$-rays. Four new bands including a $\Delta J=1$ sequence have been identified and all the earlier reported bands, other than the yrast band, have been extended to higher spins and excitation energy. The spin assignments for most of the newly reported levels have been made using the observed coincidence angular anisotropy. Tilted axis cranking calculations support the interpretation of two of the observed magnetic dipole sequences as examples of magnetic rotational bands.

We investigated systematically whether the $S$-wave ($\overline{Q}q$) meson and the ($Q\overline{q}$) meson may form $S$-wave bound states in a chiral SU(3) quark model by solving the resonating group method equation. Here $Q=c$ or $b$ and $q=u,d$, or $s$. Our preliminary calculation disfavors the existence of $I=\frac{1}{2}(\overline{Q}l)\text{−}(Q\overline{s})$ molecules ($l=u,d$) but favors the existence of isoscalar $B\overline{B}$, $B^{*}{\overline{B}}^{*}(J=2)$, and $B{\overline{B}}^{*}(C=+)$ molecules. The existence of isovector (charm-anticharm) and (charm-bottom) molecules is also disfavored. Therefore the resonance-like structure $Z^{+}(4051)$ is unlikely to be an $S$-wave $D^{*}{\overline{D}}^{*}$ molecule.

By elastic scattering of unpolarized electrons on a polarized deuteron target in the direction of the three momenta of the outgoing deuteron and by measuring the vector polarization of the final deuteron in the same direction and at the same values of squared transferred momenta $t$ as the unpolarized elastic electron-deuteron cross-section is measured, one can find out all three deuteron electromagnetic form factors in the space-like region.

The multiplicities of postsaddle protons and $\alpha$ particles of the heavy systems ${}^{234}\mathrm{Cf}$, ${}^{240}\mathrm{Cf}$, ${}^{246}\mathrm{Cf}$, and ${}^{240}\mathrm{U}$ as functions of the postsaddle dissipation strength are calculated in the framework of a dynamical Langevin model coupled with a statistical decay model. It is found that with increasing isospin of the Cf system, the sensitivity of the postsaddle proton and $\alpha$-particle multiplicity to the dissipation strength decreases substantially, and it disappears for the ${}^{240}\mathrm{U}$ system. We suggest that on the experimental side, to accurately probe the postsaddle dissipation strength by measuring the prescission proton and $\alpha$-particle multiplicity, it is best to populate heavy compound systems with low isospin.

The generalized Gerasimov-Drell-Hearn sum rule is evaluated for the contribution of single pion production on the deuteron by explicit integration up to an energy of 1.5 GeV for both coherent and incoherent production. As the elementary ${\gamma }^{*}N\to \pi N$ amplitude, the MAID2003 model has been used. For incoherent production, the final state interaction is included in the final $\mathit{NN}$ and $\pi N$ subsystems. The resulting contribution to the generalized transverse GDH sum rule is considerably smaller than the negative contribution from the disintegration channel $d(e,e^{\text{'}})\mathit{np}$, which dominates the sum rule at low $Q^2$.

By considering the effect of shear viscosity we have investigated the evolution of a chemically equilibrating quark-gluon plasma at finite baryon density. Based on the evolution of the system we have performed a complete calculation for the dilepton production from the following processes: $q\overline{q}\to l\overline{l}$, $q\overline{q}\to \mathit{gl}\overline{l}$, Compton-like scattering ($\mathit{qg}\to \mathit{ql}\overline{l},\overline{q}g\to \overline{q}l\overline{l}$), gluon fusion ($g\overline{g}\to c\overline{c}$), annihilation ($q\overline{q}\to c\overline{c}$), as well as the multiple scattering of quarks. We have found that quark-antiquark annihilation, Compton-like scatterring, gluon fusion, and multiple scattering of quarks give important contributions. Moreover, we have also found that the dilepton yield is an increasing function of the initial quark chemical potential, and the increase of the quark phase lifetime because of the viscosity also obviously raises the dilepton yield.

Within a chiral constituent quark model approach, $\eta$-meson production on the proton via electromagnetic and hadron probes is studied. With few parameters, the differential cross section and polarized beam asymmetry for $\gamma p\to \eta p$ and differential cross section for ${\pi }^{-}p\to \eta n$ processes are calculated and successfully compared with the data in the center-of-mass energy range from threshold up to 2 GeV. The five known resonances $S_{11}(1535)$, $S_{11}(1650)$, $P_{13}(1720)$, $D_{13}(1520)$, and $F_{15}(1680)$ are found to be dominant in the reaction mechanisms in both channels. Possible roles played by new resonances are also investigated; and in the photoproduction channel, significant contribution from $S_{11}$ and $D_{15}$ resonances, with masses around 1715 and 2090 MeV, respectively, are deduced. For the so-called missing resonances, no evidence is found within the investigated reactions. The helicity amplitudes and decay widths of $N^{*}\to \pi N$, $\eta N$ are also presented and found to be consistent with the Particle Data Group values.

The multipole mixing ratios of $\Delta I=1$ transitions between levels in rotational bands built on single-particle states in odd neutron nuclei are dependent on the configurations of the states. In particular, the mixing ratio can be used to distinguish between several possible single-particle configurations if interpreted with the particle-axial-rotor model. This work features the first determination of the ground-state configurations of ${}^{109,111}\mathrm{Ru}$. The single-particle structures of the ground states of ${}^{101}\mathrm{Zr}$ and ${}^{103,105,107}\mathrm{Mo}$ as well as excited states in ${}^{103,107}\mathrm{Mo}$ are also investigated, with a new result found in ${}^{107}\mathrm{Mo}$.

We study the transition from the $\gamma$-rigid to $\gamma$-soft collective nuclear dynamics across the Casten triangle of the interacting boson model using mean-field techniques and confront the description with the exact diagonalization. We inspect the domain of validity of the SU(3) quasidynamical symmetry inside the Casten triangle and reveal critical behavior within the low-lying excited spectrum due to a degeneracy of $\beta$ and $\gamma$ vibrations.

The polarization charges in ${}^{44,46,48}\mathrm{Ti}$ are studied by the microscopic particle-vibration model and used to investigate the electric quadrupole transitions of the yrast terminating bands. The validity of the commonly used empirical effective charges in the $\mathit{pf}$ shell-model calculations is confirmed. The quadrupole transition probabilities $B(E2,I\to I-2)$ and electromagnetic moments are reasonably well reproduced compared with experimental results. It is found that a globally decreasing $B(E2)$ is accompanied with convergence of valence particles into the $1f_{7/2}$ shell when approaching the terminating states. The $I=6^{+}$ state in ${}^{48}\mathrm{Ti}$ shows an exotic behavior with an irregularity of $B(E2)$ and sign change of electromagnetic moments, which is related to a neutron-dominant prolate shape.

The development of deformation and shape coexistence in the vicinity of doubly magic ${}^{48}\mathrm{Ca}$, related to the weakening of the $N=28$ shell closure, was addressed in a low-energy Coulomb excitation experiment using a radioactive ${}^{44}\mathrm{Ar}$ beam from the SPIRAL facility at GANIL. The $2_1^{+}$ and $2_2^{+}$ states in ${}^{44}\mathrm{Ar}$ were excited on ${}^{208}\mathrm{Pb}$ and ${}^{109}\mathrm{Ag}$ targets at two different beam energies. $B(E2)$ values between all observed states and the spectroscopic quadrupole moment of the $2_1^{+}$ state were extracted from the differential Coulomb excitation cross sections, indicating a prolate shape of the ${}^{44}\mathrm{Ar}$ nucleus and giving evidence of an onset of deformation already two protons and two neutrons away from doubly magic ${}^{48}\mathrm{Ca}$. New Hartree-Fock-Bogoliubov based configuration mixing calculations have been performed with the Gogny D1S interaction for ${}^{44}\mathrm{Ar}$ and neighboring nuclei using two different approaches: the angular momentum projected generator coordinate method considering axial quadrupole deformations and a five-dimensional approach including the triaxial degree of freedom. The experimental values and new calculations are furthermore compared to shell-model calculations and to relativistic mean-field calculations. The new results give insight into the weakening of the $N=28$ shell closure and the development of deformation in this neutron-rich region of the nuclear chart.

Much effort has been invested on effective-field-theoretical studies of the near-threshold $\mathit{NN}\to \mathit{NN}\pi$ reactions and, in order to deal with the somewhat large three-momentum transfers involved, the momentum counting scheme (MCS) was proposed as an alternative to the usual Weinberg counting scheme. Given the fact that a quantitative explanation of the existing high-precision $\mathit{NN}\to \mathit{NN}\pi$ data requires a careful examination of higher chiral order contributions to the transition operator, we make a detailed numerical investigation of the convergence property of MCS for a pilot case of the $\mathit{pp}\to \mathit{pp}{\pi }^0$ reaction. Our study indicates that MCS is superior to the Weinberg scheme in identifying dominant higher order contributions to the $\mathit{NN}\to \mathit{NN}\pi$ reactions.

The centrality dependence of the midrapidity charged-particle multiplicity density ($\left|\eta \right|<1$) is presented for $\mathrm{Au}+\mathrm{Au}$ and $\mathrm{Cu}+\mathrm{Cu}$ collisions at RHIC over a broad range of collision energies. The multiplicity measured in the $\mathrm{Cu}+\mathrm{Cu}$ system is found to be similar to that measured in the $\mathrm{Au}+\mathrm{Au}$ system, for an equivalent $N_{\mathrm{part}}$, with the observed factorization in energy and centrality still persistent in the smaller $\mathrm{Cu}+\mathrm{Cu}$ system. The extent of the similarities observed for bulk particle production is tested by a comparative analysis of the inclusive transverse momentum distributions for $\mathrm{Au}+\mathrm{Au}$ and $\mathrm{Cu}+\mathrm{Cu}$ collisions near midrapidity. It is found that, within the uncertainties of the data, the ratio of yields between the various energies for both $\mathrm{Au}+\mathrm{Au}$ and $\mathrm{Cu}+\mathrm{Cu}$ systems are similar and constant with centrality, both in the bulk yields and as a function of $p_T$, up to at least 4 GeV/$c$. The effects of multiple nucleon collisions that strongly increase with centrality and energy appear to only play a minor role in bulk and intermediate transverse momentum particle production.

We investigate the $\alpha$-decay half-lives of the exotic $N=125,126,127$ isotones by the generalized density-dependent cluster model (GDDCM) in combination with the microscopic two-level model. The decay widths are calculated using the overlap integral of the quasibound state wave function, the scattering state wave function, and the difference of potentials, instead of using the simple semiclassical WKB method along with the Bohr-Sommerfeld quantization condition. The $\alpha$-preformation factors are evaluated by the $Z$-dependent formula based on the two-level model, where the closed-shell effect is included. The calculated half-lives of $\alpha$ transitions to both ground states and excited states are found to be in good agreement with the experimental data.