The pseudorapidity distributions of charged particles produced in deuteron-gold ($d$-Au) and proton-emulsion ($p$-Em) collisions at high energies are studied in the framework of the two-cylinder model. The experimental results of nuclear reactions induced by protons and deuterons [$p(d)A$ collisions] can be simply described by this model. The dependencies of parameter values on centrality for $d$-Au collisions and on nucleon-nucleon center-of-mass energy for $p$-Em collisions are obtained. The formula obtained by this model is a unified formula in the description of (pseudo)rapidity distributions of final-state particles produced in different interactions over an energy range from intermediate accelerator energy to ultrahigh cosmic-ray energy.

The light vector mesons ($\rho$,$\omega$, and $\varphi$) were produced in deuterium, carbon, titanium, and iron targets in a search for possible in-medium modifications to the properties of the $\rho$ meson at normal nuclear densities and zero temperature. The vector mesons were detected with the CEBAF Large Acceptance Spectrometer (CLAS) via their decays to $e^{+}{e}^{-}$. The rare leptonic decay was chosen to reduce final-state interactions. A combinatorial background was subtracted from the invariant mass spectra using a well-established event-mixing technique. The $\rho$-meson mass spectrum was extracted after the $\omega$ and $\varphi$ signals were removed in a nearly model-independent way. Comparisons were made between the $\rho$ mass spectra from the heavy targets ($A>2$) with the mass spectrum extracted from the deuterium target. With respect to the $\rho$-meson mass, we obtain a small shift compatible with zero. Also, we measure widths consistent with standard nuclear many-body effects such as collisional broadening and Fermi motion.

Within the neutron-proton interacting boson model we study the population of mixed-symmetry states via $\alpha$ transfer processes. Closed expressions are deduced in the case of the limiting $U_{\pi +\nu }(5)$ and ${\mathit{SU}}_{\pi +\nu }(3)$. We find that the population of the lowest mixed-symmetry $2^{+}$ state, vanishing along the $N_{\pi }=N_{\nu }$ line, depends on the number of active bosons and is normally smaller than that of the lowest full symmetric $2^{+}$ state. In particular, for deformed nuclei where the number of bosons is normally large, the relative population of the mixed-symmetry $2^{+}$ state is of the order of a few percent. More favorable cases can be found near shell closures, as in the case of $\alpha$ transfer leading to ${}^{140}\mathrm{Ba}$.

An excitation function for the fusion reaction ${}^{28}\mathrm{Si}$ $+$ ${}^{30}\mathrm{Si}$ ($Q=14.3\mathrm{MeV}$) has been measured down to $40\mu b$. Deviations from the behavior predicted by the optical model and standard coupled-channels calculations have been observed in this system. The fusion cross sections can be reproduced by a shallow potential model well, which was originally developed to explain the hindrance of heavy-ion fusion for systems with negative $Q$-values.

A methodology for extracting neutron direct capture rates from Coulomb dissociation data is developed and applied to the Coulomb dissociation of ${}^{15}\mathrm{C}$ on ${}^{208}\mathrm{Pb}$ at 68 MeV/nucleon. Full continuum discretized coupled channel calculations are performed and an asymptotic normalization coefficient is determined from a fit to the breakup data. Direct neutron capture calculations using the extracted asymptotic normalization coefficient provide $(n,\gamma )$ cross sections consistent with direct measurements. Our results show that the Coulomb dissociation data can be reliably used for extracting the cross section for ${}^{14}\mathrm{C}$($n,\gamma$)${}^{15}\mathrm{C}$ if the appropriate reaction theory is used. The resulting error bars are of magnitude comparable to those from the direct measurement. This procedure can be used more generally to extract capture cross sections from breakup reactions whenever the desired capture process is fully peripheral.

We studied analogs of the giant dipole resonance (GDR) and spin-dipole resonance (SDR) in ${}^4\mathrm{He}$ and in the α clusters of ${}^{6,7}\mathrm{Li}$ via the (${}^7\mathrm{Li}$,${}^7\mathrm{Be}$γ) reactions on ${}^4\mathrm{He}$, ${}^6\mathrm{Li}$, and ${}^7\mathrm{Li}$ at an incident energy of 455 MeV and at a scattering angle of $0°$ by measuring spin-nonflip and spin-flip spectra. The reaction $Q$-values for the analogs of the GDR and SDR in the α clusters of ${}^{6,7}\mathrm{Li}$ were found to be more negative than those in ${}^4\mathrm{He}$ by $2.0\pm 0.5$ MeV. The ratios of the cross section for the analog of the GDR to that for the analog of the SDR in ${}^4\mathrm{He}$ and in the α clusters of ${}^6\mathrm{Li}$ and ${}^7\mathrm{Li}$ were found to be the same within errors, $0.5\pm 0.1$. The cross sections for the analogs of the GDR as well as those for the analogs of the SDR in the α clusters of ${}^{6,7}\mathrm{Li}$ were 0.6∼0.8 times smaller than those in ${}^4\mathrm{He}$. These results suggest that excitations of α clusters embedded in nuclei are suppressed as compared with excitations of free α particles.

The triaxial rotor model with independent inertia and electric quadrupole tensors is applied to the description of the extensive set of $E2$ matrix elements available for ${}^{186,188,190,192}\mathrm{Os}$. Most large and medium transition $E2$ matrix elements can be reproduced to within $~10\%,$ and most diagonal elements to within $~30\%$. Most small transition matrix elements can be reproduced to within $~30\%,$ and they support the interference effect exhibited by the model between the inertia and $E2$ tensors: this is a new feature of quantum rotor models. The diagonal $E2$ matrix elements at higher spins in the $K=2$ band are extremely sensitive to admixtures of higher $K$ values: the low experimental values in ${}^{190,192}\mathrm{Os}$ indicate significant admixtures of $K=4$ components. Attention is given to the $K^{\pi }=4^{+}$ bands in these nuclei and the controversial issue of whether they are of quadrupole or hexadecapole nature.

Azimuthal angle ($\Delta \varphi$) correlations are presented for a broad range of transverse momentum ($0.4<p_T<10$ GeV/$c$) and centrality (0–92%) selections for charged hadrons from dijets in Au+Au collisions at $\sqrt{s_{\mathit{NN}}}=200$ GeV. With increasing $p_T$, the away-side $\Delta \varphi$ distribution evolves from a broad and relatively flat shape to a concave shape, then to a convex shape. Comparisons with $p+p$ data suggest that the away-side distribution can be divided into a partially suppressed “head” region centered at $\Delta \varphi ~\pi$, and an enhanced “shoulder” region centered at $\Delta \varphi ~\pi \pm 1.1$. The $p_T$ spectrum for the associated hadrons in the head region softens toward central collisions. The spectral slope for the shoulder region is independent of centrality and trigger $p_T$. The properties of the near-side distributions are also modified relative to those in $p+p$ collisions, reflected by the broadening of the jet shape in $\Delta \varphi$ and $\Delta \eta$, and an enhancement of the per-trigger yield. However, these modifications seem to be limited to $p_T\lesssim 4$ GeV/$c$, above which both the hadron pair shape and per-trigger yield become similar to $p+p$ collisions. These observations suggest that both the away- and near-side distributions contain a jet fragmentation component which dominates for $p_T\gtrsim 5$ GeV/$c$ and a medium-induced component which is important for $p_T\lesssim 4$ GeV/$c$. We also quantify the role of jets at intermediate and low $p_T$ through the yield of jet-induced pairs in comparison with binary scaled $p+p$ pair yield. The yield of jet-induced pairs is suppressed at high pair proxy energy (sum of the $p_T$ magnitudes of the two hadrons) and is enhanced at low pair proxy energy. The former is consistent with jet quenching; the latter is consistent with the enhancement of soft hadron pairs due to transport of lost energy to lower $p_T$.

The medium-spin structure of the neutron-rich, odd-odd nucleus ${}^{94}\mathrm{Rb}$ was studied by means of γ-ray spectroscopy. Excited levels were populated in the neutron-induced fission of ${}^{235}\mathrm{U}$ and in the spontaneous fission of ${}^{252}\mathrm{Cf}$ and ${}^{248}\mathrm{Cm}$. Two isomeric states were found at 1485.2 and 2074.8 keV with half-lives of 18 and 107 ns, respectively. The probable structures of the two isomers involve the fully aligned, proton-neutron configurations $[\pi (g_{9/2})\otimes \nu (g_{7/2})]{}_{8^{+}}$ and $[\pi (g_{9/2})\otimes \nu (h_{11/2})]{}_{{10}^{-}}$, respectively. These new data give information on the single-particle energies in the region.

Two-quasineutron states in ${}^{248}\mathrm{Cf}$ and ${}^{250}\mathrm{Cf}$ were investigated by single-neutron transfer reactions, ${}^{249}\mathrm{Cf}$($d,t$)${}^{248}\mathrm{Cf}$ and ${}^{249}\mathrm{Cf}$($d,p$)${}^{250}\mathrm{Cf}$. The majority of levels observed were assigned to 12 bands in ${}^{248}\mathrm{Cf}$ and six bands in ${}^{250}\mathrm{Cf}$, constructed from the single-particle states in neighboring Cf nuclei. The effective two-body interactions between two odd neutrons coupled outside a deformed core were deduced from the differences in the energies of the bandheads formed by the parallel and antiparallel coupling of the intrinsic spins of the two single-particle states.

A spin-isospin-dependent three-dimensional approach based on momentum vectors for formulation of the three-nucleon bound state is presented in this article. The three-nucleon Faddeev equations with two-nucleon interactions are formulated as a function of vector Jacobi momenta, specifically the magnitudes of the momenta and the angle between them with the inclusion of the spin-isospin quantum numbers, without employing a partial wave decomposition. As an application the spin-isospin-dependent Faddeev integral equations are solved with Bonn-B potential. Our result for the Triton binding energy with the value of $-8.152$ MeV is in good agreement with the achievements of the other partial wave based methods.

Dipole-strength distributions in the nuclides ${}^{98}\mathrm{Mo}$ and ${}^{100}\mathrm{Mo}$ up to the neutron-separation energies have been studied in photon-scattering experiments at the bremsstrahlung facility of the Forschungszentrum Dresden-Rossendorf. To determine the dipole-strength distributions up to the neutron-emission thresholds, statistical methods were developed for the analysis of the measured spectra. The measured spectra of scattered photons were corrected for detector response and atomic background by simulations using the code GEANT3. Simulations of $\gamma$-ray cascades were performed to correct the intensities of the transitions to the ground state for feeding from higher-lying levels and to determine their branching ratios. The photoabsorption cross sections obtained for ${}^{98}\mathrm{Mo}$ and ${}^{100}\mathrm{Mo}$ from the present $(\gamma ,{\gamma }^{\text{'}})$ experiments are combined with $(\gamma ,n)$ data from literature, resulting in a photoabsorption cross section covering the range from 4 to about 15 MeV of interest for network calculations in nuclear astrophysics. Novel information about the low-energy tail of the giant dipole resonance and its energy dependence is derived. The photoabsorption cross sections deduced from the present photon-scattering experiments are compared with existing data from neutron capture and ${}^3\mathrm{He}$-induced reactions.

Self-consistent axially symmetric Skyrme Hartree-Fock plus BCS calculations are performed to study the evolution of shapes with the number of nucleons in various chains of Yb, Hf, W, Os, and Pt isotopes from neutron number $N=110$ up to $N=122$. Potential energy curves are analyzed in a search for signatures of oblate-prolate phase shape transitions, and results from various Skyrme and pairing forces are considered. Comparisons with results obtained with the Gogny interaction as well as with relativistic mean field calculations are presented. The role of the γ degree of freedom is also discussed.

High-spin states of ${}^{156}\mathrm{Yb}$ have been studied via the ${}^{144}\mathrm{Sm}$(${}^{16}\mathrm{O}$,$4n$)${}^{156}\mathrm{Yb}$ fusion-evaporation reaction at beam energy 102 MeV. The positive-parity yrast band and negative-parity cascade have been extended up to higher-spin states, respectively. In the present work, the negative-parity sequence above the ${25}^{-}$ state was found to be irregular and fragment into many parallel branches. This pattern may related to the excitation from the nucleon in the $Z=64,N=82$ core. The characteristics of alignment plot and E-GOS curve for the positive-parity yrast sequence in ${}^{156}\mathrm{Yb}$ indicate that this nucleus may undergo an evolution from quasivibrational to quasirotational structure with increasing angular momentum. Based on a systematic summary of the available experimental alignments for the even-$A$ ${}^{156,158,160,162,164}\mathrm{Yb}$ isotopes, the structural evolutions induced by the increase in angular momentum, as well as by the change in neutron numbers, in these even-$A$ Yb isotopes have been discussed in comparison with the cranked Woods-Saxon-Strutinsky calculations by means of total-Routhian-surface (TRS) methods.

In this article we report the results of detailed interacting boson model calculations with configuration mixing for the neutron-deficient Pb isotopes. Calculated energy levels and $B(E2)$ values for ${}^{188-196}\mathrm{Pb}$ are discussed and some care is suggested concerning the current classification on the basis of level systematics of the $4_1^{+}$ and $6_1^{+}$ states in ${}^{190-194}\mathrm{Pb}$. Furthermore, quadrupole deformations are extracted for ${}^{186-196}\mathrm{Pb}$ and the mixing between the different families (0p-0h, 2p-2h, and 4p-4h) is discussed in detail. Finally, the experimental and the theoretical level systematics are compared.

We present a description of nuclear spontaneous fission, and generally of quantum tunneling, in terms of instantons, that is, periodic imaginary-time solutions to time-dependent mean-field equations. This description allows comparisons to be made with the more familiar generator coordinate (GCM) and adiabatic time-dependent Hartree-Fock (ATDHF) methods. It is shown that the action functional whose value for the instanton is the quasiclassical estimate of the decay exponent fulfills the minimum principle when additional constraints are imposed on trial fission paths. In analogy with mechanics, these are conditions of energy conservation and the velocity-momentum relations. In the adiabatic limit, the instanton method reduces to the time-odd ATDHF equation, with collective mass including the time-odd Thouless-Valatin term, while the GCM mass completely ignores velocity-momentum relations. This implies that GCM inertia generally overestimates the instanton-related decay rate. The very existence of the minimum principle offers hope for a variational search for instantons. After the inclusion of pairing, the instanton equations and the variational principle can be expressed in terms of the imaginary-time-dependent Hartree-Fock-Bogoliubov (TDHFB) theory. The adiabatic limit of this theory reproduces ATDHFB inertia.

Measurements of Bose-Einstein correlations of ${\pi }^{-}{\pi }^{-}$ pairs in central Pb+Pb collisions were performed with the NA49 detector at the CERN Super Proton Synchroton for beam energies of $20A,30A,40A,80A$, and $158A$ GeV. Correlation functions were measured in the longitudinally comoving “out-side-long” reference frame as a function of rapidity and transverse momentum in the forward hemisphere of the reaction. Radius and correlation strength parameters were obtained from fits of a Gaussian parametrization. The results show a decrease of the radius parameters with increasing transverse-momentum characteristic of strong radial flow in the pion source. No striking dependence on pion-pair rapidity or beam energy is observed. Static and dynamic properties of the pion source are obtained from simultaneous fits with a blast-wave model to radius parameters and midrapidity transverse-momentum spectra. Predictions of hydrodynamic and microscopic models of Pb+Pb collisions are discussed.

Neutrino emission in processes of breaking and formation of neutron and proton Cooper pairs is calculated within the Larkin-Migdal-Leggett approach for a superfluid Fermi liquid. We demonstrate explicitly that the Fermi-liquid renormalization respects the Ward identity and ensures the weak vector-current conservation. The systematic expansion of the emissivities for small temperatures and nucleon Fermi velocity $v_{\mathrm{F},i},i=n,p,$ is performed. Both neutron and proton processes are mainly controlled by the axial-vector current contributions, which are not strongly changed in the superfluid matter. Thus, compared to earlier calculations, the total emissivity of processes on neutrons paired in the $1S_0$ state is suppressed by a factor of $\simeq (0.9\text{−}1.2)v_{\mathrm{F},n}^2$. A similar suppression factor ($~v_{\mathrm{F},p}^2$) arises for processes on protons.

We estimate electromagnetic (ultraperipheral) and strong contributions to $d+\mathrm{Au}$ soft coherent inelastic diffraction at RHIC, $d+\mathrm{Au}$ $\to X+$Au. We show that the electromagnetic contribution is the dominant one and that the corresponding cross section is sizable, ${\sigma }_{\mathrm{e}.\mathrm{m}.}^{d+\mathrm{Au}\to X+\mathrm{Au}}=214$ mb, which constitutes 10% of the total $d\mathrm{Au}$ inelastic cross section.

The scattering of a weakly bound three-body system by a target is discussed. A transformed harmonic oscillator basis is used to provide an appropriate discrete and finite basis for treating the continuum part of the spectrum of the projectile. The continuum-discretized coupled-channels framework is used for the scattering calculations. The formalism is applied to different reactions, ${}^6\mathrm{He}$$+$${}^{12}\mathrm{C}$ at 229.8 MeV, ${}^6\mathrm{He}$$+$${}^{64}\mathrm{Zn}$ at 10 and 13.6 MeV, and ${}^6\mathrm{He}$$+$${}^{208}\mathrm{Pb}$ at 22 MeV, induced by the Borromean nucleus ${}^6\mathrm{He}$. Both the Coulomb and nuclear interactions with a target are taken into account.