Measurements of the ${}^{14}\mathrm{C}$(${}^{14}\mathrm{C}$,${}^{14}\mathrm{C}$[${}^{10}\mathrm{Be}$+$\alpha$]) breakup reaction have been made at a beam energy of 98.2 MeV. The studies were performed with two charged-particle telescopes that permitted the energy, mass, charge, and emission angle of each detected particle to be determined. A series of ${}^{14}\mathrm{C}$ excited states at energies of 14.3, 14.8 15.6, 16.4, 17.3, 18.6, 19.8, 20.6, and 21.6 MeV was observed to decay to either the ${}^{10}\mathrm{Be}$ ground state or the first excited states. Angular correlation measurements suggest an assignment of $J^{\pi }=3^{-}$ for the 15.6 MeV state.

In recent years, an energetic experimental program has set quite stringent limits on a possible “non-$1/r^2$” dependence on gravity at short length scales. This effort has been largely driven by the predictions of theories based on compactification of extra spatial dimensions. It is characteristic of many such theories that the strength and length scales of such anomalous gravity are not clearly determined from first principles. As a result, it is productive to extend the current limits the range and strength of such hypothetical interactions. As a heavy, neutral, and (almost) stable particle, the neutron provides an ideal probe for the study of such hypothetical interactions at very short range. In this work, we describe methods based on neutron interferometry which have the capability to provide improved sensitivity non-Newtonian forces down to length scales at and below an nanometer.

For the first time, non-yrast structures of the neutron mid-shell nucleus ${}^{186}\mathrm{Pb}$ have been identified in an in-beam γ-ray spectroscopy measurement using the recoil-decay tagging technique. The yrast band has been tentatively extended up to $I^{\pi }=20{}^{+},$ revealing a similar backbend to that observed in the Pt and Hg isotones. Three new bands and several other transitions have been observed. Calculations carried out in the framework of the interacting boson model together with mean-field studies using the generator coordinate method provide arguments for the association of one of the new bands with an oblate shape. The present data also show evidence for octupole and γ-vibrational bands.

Experimental analyses of moderate-temperature nuclear gases produced in the violent collisions of 35 MeV/nucleon ${}^{64}\mathrm{Zn}$ projectiles with ${}^{92}\mathrm{Mo}$ and ${}^{197}\mathrm{Au}$ target nuclei reveal a large degree of α particle clustering at low densities. For these gases, temperature- and density-dependent symmetry energy coefficients have been derived from isoscaling analyses of the yields of nuclei with $A⩽4$. At densities of 0.01 to 0.05 times the ground-state density of symmetric nuclear matter, the temperature- and density-dependent symmetry energies range from 9.03 to 13.6 MeV. This is much larger than those obtained in mean-field calculations and reflects the clusterization of low-density nuclear matter. The results are in quite reasonable agreement with calculated values obtained with a recently proposed virial equation of state calculation.

The low-spin structure of ${}^{94}\mathrm{Zr}$ has been studied with the ($n$,$n^{\text{'}}$γ) reaction, and branching ratios, lifetimes, multipolarities and spin assignments were determined. The $2_2^{+}$ state at 1671.4 keV has been identified as the lowest mixed-symmetry state in ${}^{94}\mathrm{Zr}$. The 752.5-keV transition from this state to the $2_1^{+}$ level has a large $B(M1)$ value of 0.33(5) ${\mu }_N^2$, and the $B(E2)$ of the transition to the ground state has an unusually large value of 8(1) W.u. The $M1$ transition strength is in agreement with IBM-2 predictions in the U(5) vibrational limit, whereas the large $B(E2;2_{1,\mathrm{MS}}^{+}\to 0_1^{+}$) value significantly exceeds the $E2$ strength predicted by the IBM-2. For the first time, the $2_{1,\mathrm{MS}}^{+}\to 0_1^{+}E2$ transition is observed to have a larger $E2$ transition strength than the $2_1^{+}\to 0_1^{+}$ decay.

The phase diagram of two-level boson Hamiltonians, including the interacting boson model (IBM), is studied beyond the standard mean field approximation using the Holstein-Primakoff mapping. The limitations of the usual intrinsic state (mean field) formalism concerning finite-size effects are pointed out. The analytic results are compared to numerics obtained from exact diagonalizations. Excitation energies and occupation numbers are studied in different model space regions (Casten triangle for IBM) and especially at the critical points.

The rates governing momentum broadening in a quark-gluon plasma with a momentum anisotropy are calculated to leading-log order for a heavy quark using kinetic theory. It is shown how the problematic singularity for these rates at leading order is lifted by next-to-leading-order gluon self-energy corrections to give a finite contribution to the leading-log result. The resulting rates are shown to lead to larger momentum broadening along the beam axis than in the transverse plane, which is consistent with recent STAR results. This might indicate that the quark-gluon-plasma at RHIC is not in equilibrium.

On a bounded, measurable domain of non-negative current-quark mass, realistic models of the QCD gap equation can simultaneously admit two nonequivalent dynamical chiral symmetry breaking (DCSB) solutions and a solution that is unambiguously connected with the realization of chiral symmetry in the Wigner mode. The Wigner solution and one of the DCSB solutions are destabilized by a current-quark mass, and both disappear when that mass exceeds a critical value. This critical value also bounds the domain on which the surviving DCSB solution possesses a chiral expansion. This value can therefore be viewed as an upper bound on the domain within which a perturbative expansion in the current-quark mass around the chiral limit is uniformly valid for physical quantities. For a pseudoscalar meson constituted of equal-mass current quarks, it corresponds to a mass $m_{0^{-}}~0.45$ GeV. In our discussion, we employ properties of the two DCSB solutions of the gap equation that enable a valid definition of $\langle \overline{q}q\rangle$ in the presence of a nonzero current mass. The behavior of this condensate indicates that the essentially dynamical component of chiral symmetry breaking decreases with increasing current-quark mass.

The double neutron-proton differential transverse flow taken from two reaction systems using different isotopes of the same element is studied at incident beam energies of 400 and 800 MeV/nucleon within the framework of an isospin- and momentum-dependent hadronic transport model IBUU04. The double differential flow is found to retain about the same sensitivity to the density dependence of the nuclear symmetry energy as the single differential flow in the more neutron-rich reaction. Because the double differential flow reduces significantly both the systematic errors and the influence of the Coulomb force, it is thus more effective probe for the high-density behavior of the nuclear symmetry energy.

In a recent paper Nayak uses the “infinite nuclear matter” model to argue that all shell effects are quenched at both drip lines. We claim here that this argument is invalid.

The proton and deuteron analyzing powers and ten of the possible 12 spin correlation coefficients have been measured for $p+d$ elastic scattering at proton bombarding energies of 135 and 200 MeV. The results are compared with Faddeev calculations using two different $\mathit{NN}$ potentials. The qualitative features of the extensive data set on the spin dependence in $p+d$ elastic scattering over a wide range of angles presented here are remarkably well explained by two-nucleon force predictions without inclusion of a three-nucleon force. The remaining discrepancies are, in general, not alleviated when theoretical three-nucleon forces are included in the calculations.

We extend the renormalization of the $\mathit{NN}$ interaction with chiral two-pion exchange potential to the calculation of noncentral partial wave phase shifts with total angular momentum $j⩽5$. The short distance singularity structure of the potential, as well as the requirement of orthogonality conditions on the wave functions, determines exactly the number of undetermined parameters after renormalization.

A new model for short-range isoscalar currents in the deuteron and in the $\mathit{NN}$ system is developed. The model is based on the generation of an intermediate dressed dibaryon, which is the basic ingredient for the medium- and short-range $\mathit{NN}$ interaction proposed recently by the present authors. The new current model has only one free parameter, which has a clear physical meaning. Our calculations have demonstrated that this new current model can very well describe the experimental data for three basic deuteron observables of isoscalar magnetic type: the magnetic moment, the circular polarization of the photon in the $\overrightarrow{n}p\to d\overrightarrow{\gamma }$ process at thermal neutron energies, and the structure function $B(Q^2)$ up to $Q^2\simeq 2{\mathrm{GeV}}^2/c^2$.

The general form of the cross section as well as the polarizations of electron-deuteron elastic scattering are given. Two-photon exchange effects are analyzed. Possible signatures of the two-photon exchange effects in the electron-deuteron elastic scattering are discussed.

The structure of the ${}^{56,58,60}\mathrm{Cr}$ nuclei was investigated at Gammasphere using both deep inelastic and fusion-evaporation reactions. As a result of this work, expanded level schemes are now available for these three neutron-rich, even-even isotopes. Experimental signatures were found for both single-particle and collective excitations whose relative importance varies with neutron number. Together with recent structural information on the odd-$A$ ${}^{55,57,59}\mathrm{Cr}$ neighbors, the present data highlight the changing role of the $g_{9/2}$ orbital with neutron number. Comparisons with shell-model calculations using the recently developed GXPF1A interaction and with total Routhian surface calculations are presented.

The energies of the degenerate spin-flip doublet $(3^{+}/2,5^{+}/2)$ of ${}_{\Lambda }^9\text{Be}$ and of the $2^{+}$ state of ${}_{\Lambda \Lambda }^{10}\text{Be}$ are analyzed in the α cluster model using a phenomenological dispersive three-body $\Lambda \alpha \alpha$ force that reproduces the ground state energy of ${}_{\Lambda }^9\text{Be}$. Two types of phenomenological $\Lambda \alpha$ and $\alpha \alpha$ potentials and a few s-state $\Lambda \Lambda$ potentials are taken as input. The energies of the excited states of the hypernuclei, treated as three- and four-body systems, calculated using the Variational Monte Carlo method, are in good agreement with the experimental values. Our results demonstrate that the existing data are insensitive to whether one employs a dispersive $\Lambda \alpha \alpha$ force along with potentials in the relative angular momentum state $l=0$ and 2 as in the present work or whether one uses nonlocal $\Lambda \alpha$ potential as in earlier analyses.

Giant neutron halos in medium-heavy nuclei are studied in the framework of the Hartree-Fock-Bogoliubov (HFB) approach with Skyrme interactions. The appearance of such structures depends sensitively on the effective interaction adopted. This is illustrated by comparing the predictions of SLy4 and SkI4 in the Ca and Zr isotopic chains. The latter force predicts a neutron halo in the Zr chain with $A>122$ due to the weakly bound orbitals $3p1/2$ and $3p3/2$. It is found that the energies of states near the separation threshold depend sensitively on effective mass values. The structure of the halo is analyzed in terms of the occupation probabilities of these orbitals and their partial contributions to the neutron density. The antihalo effect is also discussed in the case of ${}^{124}\mathrm{Zr}$ by comparing the occupation probabilities and wave functions of the Hartree-Fock neutron single-particle states near the Fermi energy with the corresponding HFB quasiparticle states.

Analysis of the differential cross sections for ${}^4\mathrm{He}$ +${}^4\mathrm{He}$ elastic scattering is performed within the framework of the double-folding optical model. Two appropriate effective nucleon-nucleon interactions are employed to generate the α-α folded real potentials. The obtained potentials in conjunction with phenomenological Woods-Saxon (WS) derivative imaginary potentials are used to investigate six sets of the elastic scattering data through the energy range 100–280 MeV. Successful reproduction of the data is obtained by both considered interactions. In addition, real phenomenological potentials expressed in a squared WS form are successfully used to reproduce these data.

We estimate exclusive density and asymmetry parameter dependent dispersion relations of various charged states of pions in asymmetric nuclear matter. The possibility of matter induced mixing of ${\pi }^0$ with η is clearly exposed with the further mass modification of ${\pi }^0$ meson due to mixing. Asymmetry driven mass splitting and mixing amplitude are of the same order as the corresponding values in vacuum. Closed form analytic results for the mass shifts and dispersion relations with and without mixing are presented. Furthermore, we discuss the sensitivity of our results on the scalar mean field within the framework of quantum hadrodynamics.

We show that dynamical deformation effects play an important role in fusion reactions involving the ${}^{64}\mathrm{Ni}$ nucleus, in particular the ${}^{64}\mathrm{Ni}+{}^{132}\mathrm{Sn}$ system. We calculate fully microscopic interaction potentials and the corresponding subbarrier fusion cross-sections.