We report the experimental confirmation of the production of element 110. In the bombardment of a ${}^{208}\mathrm{Pb}$ target with a 309-MeV ${}^{64}\mathrm{Ni}$ beam, we have observed two chains of time- and position-correlated events. Each chain consisted of the implantation of an evaporation residue followed by the emission of $\alpha$ particles. We attribute these two chains to the decay of ${}^{271}110$ produced with a cross section of ${8.3}_{-5.3}^{+11\mathrm{}}\mathrm{pb}.$

The ultrarelativistic quantum molecular dynamics (UrQMD) model is incorporated with a statistical decay model aiming to describe the neutron double global-differential cross sections of $p+\mathrm{Al},$ Fe, and Zr at 1.2 GeV. Good agreement is generally obtained with the default UrQMD parameters. In particular, the UrQMD calculation with a momentum dependent Pauli potential improves the intensity of the quasielastic peak in neutron double-differential cross sections. The lower and higher energy parts of the neutron spectra at backward angles are found to be sensitive to meson-meson and meson-baryon interactions. The influence of sequential evaporation and simultaneous multifragmentation disintegration mechanisms on the neutron spectra is also investigated. It is shown that the statistical multifragmentation model is more suited for the description of the lower part of the neutron energy spectra.

Comparisons of calculated neutron yield distributions from $\alpha$-particle induced reactions on thick targets are made with measured data to analyze the initial reaction process in the framework of the exciton (hybrid) model code ALICE91 (M. Blann, Lawrence Livermore National Laboratory Report UCID 19614, 1982). We have considered two reaction mechanisms: dissolution of the $\alpha$ in the nuclear field, and preequilibrium processes initiated by $\alpha$-nucleon collisions. Both these processes seem to contribute to the emitted neutron spectra in varying proportions depending on the incident $\alpha$ energy and possibly on the target nucleus. Contributions from other processes appear to be non-negligible.

Angular distributions of the differential cross section and the induced polarization of ${}^3\mathrm{He}$ elastic scattering on ${}^{12}\mathrm{C},$ ${}^{58}\mathrm{Ni},$ and ${}^{90}\mathrm{Zr}$ targets were measured at 443 MeV incident energy. This is the first measurement of ${}^3\mathrm{He}$ spin observables at intermediate energies. Cross sections and polarizations were measured in the range of center-of-mass angles of $5°–30°$ and $5°–20°,$ respectively. The polarization was measured with the focal plane polarimeter system of the Grand Raiden spectrometer, which was calibrated for ${}^3\mathrm{He}$ at the present energy. The optical potential parameters including the spin-orbit term were determined by a systematic search procedure. The diffuseness parameter of the spin-orbit potential was about 0.6–0.8 fm in contrast to much smaller values of 0.2–0.3 fm reported at lower energies. The energy dependence of the reduced volume integrals of the optical potential was found to be similar to that observed for protons at intermediate energies, but the real potential terms were smaller. Single folding (SF) model calculations were performed and compared with the experimental data. We found that the renormalization factors used to modify the SF potential were necessary in order to obtain a good fit to the data. These results call for an appropriate density dependent nucleon-nucleus interaction in the ${}^3\mathrm{He}$ nucleus.

We show that centrality dependence of charged particle pseudorapidity density at midrapidity in $\mathrm{Au}+\mathrm{Au}$ collisions at the RHIC is well described as proportional to the number of participating constituent quarks. In this approach there is no need for an additional contribution from hard processes usually considered in the models based on the number of the nucleon participants.

The diffractive $\phi$-meson photoproduction amplitude is dominated by the Pomeron-exchange process and contains the terms that govern the spin-spin and spin-orbital interactions. We show that these terms are responsible for the spin-flip transitions at forward photoproduction angles and appear in the angular distributions of $\overrightarrow{\phi }{K}^{+}{K}^{-}$ decay in reactions with unpolarized and polarized photon beams. At large momentum transfers, the main contribution to the $\phi$-meson photoproduction is found to be due to the excitation of nucleon resonances. Combined analysis of $\omega$ and $\phi$ photoproduction indicates strong Okubo-Zweig-Iizuka–rule violation in $\phi {\mathrm{NN}}^{*}$ couplings. We also show that the spin observables are sensitive to the dynamics of $\phi$-meson photoproduction at large angles and could help to distinguish different theoretical models of nucleon resonances. Predictions for spin effects in $\phi$-meson photoproduction are presented for future experimental tests.

Neutrino emissivities in a neutron star are computed for the neutrino bremsstrahlung process. In the first part, the electroweak nucleon-nucleon bremsstrahlung is calculated in free space in terms of an on-shell T matrix using a generalized low-energy theorem. In the second part, the emissivities are calculated in terms of the hadronic polarization at the two-loop level. Various medium effects, such as finite particle width, Pauli blocking in the T matrix are considered. Compared to the pioneering work of Friman and Maxwell in terms of (antisymmetrized) one-pion exchange, the resulting emissivity is about a factor 4 smaller at saturation density.

A recoil coincidence technique has been applied to measure the $\alpha$-decay branching ratios of near-threshold states in ${}^{19}\mathrm{Ne}.$ Populating these states using the $\mathrm{}(p,t)\mathrm{}$ reaction in inverse kinematics, we detected the recoils and their decay products with 100% geometric efficiency using a magnetic spectrometer. Combining our branching ratio measurements with independent determinations of the radiative widths of these states, we calculate the astrophysical rate of ${}^{15}\mathrm{O}(\alpha ,\gamma {)}^{19}\mathrm{Ne}.$ Using this reaction rate, we perform hydrodynamic calculations of nova outbursts and conclude that no significant breakout from the hot CNO cycles into the $\mathrm{rp}$ process occurs in novae via ${}^{15}\mathrm{O}(\alpha ,\gamma {)}^{19}\mathrm{Ne}.$

From the analysis of appropriate experimental data within a simple theoretical model, it is shown that the intermediate neutron transfer channels with positive Q values really enhance the fusion cross section at sub-barrier energies. The effect is found to be very large, especially for fusion of weakly bound nuclei. New experiments are proposed, which may shed additional light on the effect of neutron transfer in fusion processes.

Non-yrast states in ${}^{80}\mathrm{Sr}$ were populated in the ${}^{24}\mathrm{Mg}{(}^{58}\mathrm{Ni}{,2p)}^{80}\mathrm{Sr}$ reaction at 200 MeV and their γ decays investigated using Gammasphere, in order to investigate shape softness and quasiparticle excitations. A large data set was collected which was A and Z gated, using the Argonne Fragment Mass Analyzer and a focal plane ion chamber. The excellent channel selection enhanced the sensitivity to energetically nonfavored configurations. Several new rotational bands were found, and many conflicts between previous experiments were resolved. In particular, the gamma vibrational band is now clearly delineated, and more than ten quasiparticle bandheads have been identified. At the highest spins, evidence for a long-predicted shape change was found.

Under the assumption that isospin T is a good quantum number, isobaric analog states and various analogous transitions among these states are expected in isobars with mass number A. Strengths of analogous Gamow-Teller (GT) and $M1\mathrm{}$ transitions have been compared for an $A=26\mathrm{}$ isobar triplet with $T_z=+1,\hspace{0.5em}0,$ and $-1,$ where $T_z$ is defined by $T_z=\left(N-Z\right)/2.\mathrm{}$ The $T_z=+\overrightarrow{1}0$ GT transitions from the $J^{\pi }{=0\mathrm{}}^{+}$ ground state of ${}^{26}\mathrm{Mg}$ to excited $J^{\pi }{=1\mathrm{}}^{+}$ states in ${}^{26}\mathrm{Al}$ were studied up to the excitation energy ${(E}_x)$ of 9 MeV by using a high energy-resolution ${(}^3\mathrm{He},t)$ reaction. The distribution of observed GT strengths was well reproduced in a shell-model calculation. The isospin symmetric $T_z=-\overrightarrow{1}0$ GT transitions can be studied in the ${}^{26}\mathrm{Si}$ $\beta$ decay. The GT strengths from the ${(}^3\mathrm{He},t)$ reaction were in good agreement with the $\beta$-decay values evaluated up to $E_x=2.7-\mathrm{MeV}$ states in ${}^{26}\mathrm{Al}.$ The GT strengths were further compared with the strengths of analogous $M1\mathrm{}$ $\gamma$ transitions in ${}^{26}\mathrm{Al},$ i.e., the $M1\mathrm{}$ transitions from the excited $1^{+}$ states to the isobaric analog state of the ${}^{26}\mathrm{Mg}$ ground state in ${}^{26}\mathrm{Al}.$ Through this comparison, contributions of spin and orbital terms in these $M1\mathrm{}$ transitions were studied. The GT and $M1\mathrm{}$ strengths as well as spin and orbital contributions in $M1\mathrm{}$ strengths are interpreted by both the shell model and the particle-rotor model assuming a correlated proton and neutron pair around a ${}^{24}\mathrm{Mg}$ core. The isospin T of each excited $1^{+}$ state in ${}^{26}\mathrm{Al}$ was also studied by examining the existence or the nonexistence of the analog $1^{+}$ state in the $T_z{=1\mathrm{}}^{26}\mathrm{Mg}$ nucleus.

The low-lying dipole strength distribution in the rare isotope ${}^{176}\mathrm{Hf}$ was studied in nuclear resonance fluorescence experiments performed at the Stuttgart Dynamitron facility using bremsstrahlung beams with end- point energies of 4.1 and 2.4 MeV. In total, about 55 excited spin-1 states, unknown so far, were observed in the excitation energy range up to 4 MeV. Detailed spectroscopic information has been obtained on excitation energies, spins, decay widths, decay branchings, and transition probabilities. Ascribing a positive parity to all observed $K=1\mathrm{}$ states, the detected total $B\left(M1\mathrm{}\right)\mathrm{}\uparrow$ strength in the energy range of the scissors mode amounts to $2.56\left(6\right)\mathrm{}{\mu }_N^2,$ nearly as much as for well-deformed midshell rare-earth nuclei. The total strength is higher than in the heavier Hf isotopes ${}^{178,180}\mathrm{Hf},$ but fits well into the systematics. The observed low-lying $\Delta K=0\mathrm{}$ transitions (with probable $E1\mathrm{}$ character) lie in the energy range around 2 MeV, as expected from the systematics. The excitation probabilities correspond to values which are characteristic for nuclei in the transitional region from deformed rotors to more $\gamma$-soft nuclei.

Nuclei far from stability are studied by solving the Hartree-Fock-Bogoliubov (HFB) equations, which describe the self-consistent mean field theory with pairing interaction. Calculations for even-even nuclei are carried out on a two-dimensional axially symmetric lattice, in coordinate space. The quasiparticle continuum wave functions are considered for energies up to 60 MeV. Nuclei near the drip lines have a strong coupling between weakly bound states and the particle continuum. This method gives a proper description of the ground state properties of such nuclei. High accuracy is achieved by representing the operators and wave functions using the technique of basis splines. The detailed representation of the HFB equations in cylindrical coordinates is discussed. Calculations of observables for nuclei near the neutron drip line are presented to demonstrate the reliability of the method.

High resolution proton resonance data have been examined for a possible parity dependence of nuclear level densities. Five spin-parity ${\mathrm{combinations}\mathrm{—}1/2}^{+},$ ${1/2}^{-},$ ${3/2}^{-},$ ${3/2}^{+},$ and ${5/2}^{+}$—have been analyzed for three ${\mathrm{datasets}\mathrm{—}}^{44}\mathrm{Ca}\mathrm{}(p,p),$ ${}^{48}\mathrm{Ti}\mathrm{}(p,p),$ and ${}^{56}\mathrm{Fe}\mathrm{}(p,p).$ Much of the uncertainty in the level density arises from the determination of the fraction of levels that are not observed. The missing fraction of levels was determined by (a) the standard width analysis method that assumes a Porter-Thomas distribution for the reduced widths and (b) a recently developed method that analyzes the spacing distribution and assumes the Wigner distribution for the nearest-neighbor spacings. There are indications of parity dependence of the level densities for several of the spin-parity combinations.

Dispersive corrections to the total cross section for high-energy scattering from a heavy nucleus are calculated using a matrix model, based on the triple-Pomeron behavior of diffractive scattering from a single nucleon, for the cross section operator connecting different states of the projectile nucleon. Energy-dependent effects due to the decrease in longitudinal momentum transfers and the opening of more channels with increasing energy are included. The three leading terms in an expansion in the number of inelastic transitions are evaluated and compared to exact results for the model in the uniform nuclear density approximation for the the scattering of nucleons from ${}^{40}\mathrm{Ca}$ and ${}^{208}\mathrm{Pb}$ for laboratory momenta ranging from 50 to $200\mathrm{GeV}/c.\mathrm{}$

In two series of high-resolution coincidence experiments at the three-spectrometer facility at MAMI, the $\mathrm{H}{(e,e}^{\prime }{\pi }^{+})X$ and ${}^2\mathrm{H}{(e,e}^{\prime }p)X$ reactions were studied to search for narrow nucleon resonances below pion threshold. The missing-mass resolution was $0.6–1.6\mathrm{MeV}{/c}^2$ full width at half maximum in the proton experiment and $0.9–1.3\mathrm{MeV}{/c}^2$ in the deuteron experiment. The experiments covered the missing-mass region from the neutron mass up to about 1050 and $1100\mathrm{MeV}{/c}^2,$ respectively. None of our measurements showed a signal for narrow resonances to a level of down to ${10}^{-4}$ with respect to the neutron peak in the missing-mass spectra.

We apply renormalization-group methods to two-body scattering by combination of known long-range and unknown short-range potentials. We impose a cutoff in the basis of distorted waves of the long-range potential and identify possible fixed points of the short-range potential as this cutoff is lowered to zero. The expansions around these fixed points define the power countings for the corresponding effective field theories. Expansions around nontrivial fixed points are shown to correspond to distorted-wave versions of the effective-range expansion. These methods applied to scattering the presence of Coulomb, Yukawa, and repulsive inverse-square potentials.

The Euclidean-time hadronic current correlation functions $G_P(\tau ,T)$ and $G_V(\tau ,T)$ of pseudoscalar and vector currents have recently been calculated in lattice simulations of QCD and have been used to obtain the corresponding spectral functions. We have used the Nambu–Jona-Lasinio (NJL) model to calculate such spectral functions, as well as the Euclidean-time correlators, and have made a comparison to the lattice results for the correlators. We find evidence for the type of temperature dependence of the NJL coupling parameters that we have used in previous studies of the mesonic confinement-deconfinement transition. We also see that the spectral functions obtained when using the maximum-entropy method and the lattice data differ from the spectral functions that we calculate in our chiral model. However, our results for the Euclidean-time correlators are in general agreement with the lattice results, with better agreement when our temperature-dependent coupling parameters are used than when temperature-independent parameters are used for the NJL model. We also discuss some additional evidence for the utility of temperature-dependent coupling parameters for the NJL model. For example, if the constituent quark mass at $T=0\mathrm{}$ is $352\mathrm{MeV}$ in the chiral limit, the transition temperature is $T_c=208\mathrm{}\mathrm{MeV}$ for the NJL model with a standard momentum cutoff parameter. (If a Gaussian momentum cutoff is used, we find $T_c=225\mathrm{}\mathrm{MeV}$ in the chiral limit, with $m=368\mathrm{}\mathrm{MeV}$ at $T=0.)$ The introduction of a weak temperature dependence for the coupling constant will move the value of $T_c$ into the range 150–170 MeV, which is more in accord with what is found in lattice simulations of QCD with dynamical quarks.

We obtain the effective-range expansion of the $\eta d$ system for seven different theoretical models of the two-body interactions. The expansion reproduces very well the theoretical scattering amplitudes for center-of-mass energies up to 100 MeV. Using this expansion we calculate the position of the $\eta \mathrm{NN}$ quasivirtual state in the complex energy plane as it is predicted by each theoretical model.

In order to determine the position of the neutron dripline for $Z=4,$ a primary beam of ${}^{40}\mathrm{Ar}$ was accelerated to 140 MeV/nucleon using the newly completed Coupled Cyclotron Facility at the National Superconducting Cyclotron Laboratory at Michigan State University. Neutron-rich fragmentation products emerging from a beryllium production target were separated with the A1900 fragment separator. The isotopes ${}^{6,8}\mathrm{He},$ ${}^{9,11}\mathrm{Li},$ ${}^{12,14}\mathrm{Be},$ ${}^{17,19}\mathrm{B},$ and ${}^{20}\mathrm{C}$ were identified using time-of-flight and energy-loss information, but no events of ${}^{16}\mathrm{Be}$ were recorded.