Low-lying proton-based intruder states have been observed in the odd-mass isotopes ${}^{189,191,193}\mathrm{Pb}$ in experiments at the RITU gas-filled recoil separator. The identification has been performed by observing the fine structure in the $\alpha$ decay of the parent ${}^{193,195,197}\mathrm{Po}$ nuclei in prompt coincidence with conversion electrons and $\gamma$ rays in the daughter lead isotopes. Along with the literature data these results establish a systematics of intruder states in the odd-mass lead isotopes from ${}^{197}\mathrm{Pb}$ down to ${}^{185}\mathrm{Pb}.$ Interpretation of these states involves the coupling of the ${1i}_{13/2}$ or ${3p}_{3/2}$ odd neutron to the $0^{+}$ state in the oblate minimum in the even-mass lead core. Conversion coefficients have been determined for some of the transitions, revealing mixing between the coexisting states. The experimental results are compared to potential energy surface calculations.

The transfer-induced fission channel has been studied in the collision of 340 MeV ${}^{28}\mathrm{Si}$ on ${}^{232}\mathrm{Th}$ as a function of the atomic number of the projectilelike fragments (PLF’s) by using a $4\pi$ detector array. It is found that the energy loss of the transfer reaction increases as a function of the net charge transfer $\Delta Z$ from the projectile to the target nucleus, going from quasielastic to deep-inelastic regimes. The average excitation energy of the targetlike fragment (TLF) is derived from the measured energy loss, whereas its angular momentum has been obtained from the angular distribution of fission fragments. It is found that the populated TLF nuclei with $Z_{\mathrm{TLF}}=90\mathrm{}–96\hspace{0.5em}(\Delta Z=0\mathrm{}–6)$ have average excitation energies up to about 100 MeV and angular momenta up to about $40ħ.$ The measured ratio of transfer-fission yield to PLF singles, $Y_f,$ first increases with increasing net charge transfer up to $\Delta Z=4\mathrm{}$ and then shows a plateau around the values $Y_f=0.4\mathrm{}–0.6$ followed by a decrease for higher $\Delta Z$ transfers. This ratio can be identified as the cumulative fission probability of the populated nuclei for net charge transfers up to $\Delta Z<~6,$ where a two-body mechanism for the first reaction step is supported by the experimental data. This result suggests a significant survival probability against fission of these TLF nuclei, in marked disagreement with the standard statistical model predictions. The observed survival probability implies that there is a strong hindrance to fission in the early stages of deexcitation, as also indicated by the large fission times ${(t}_f=10\mathrm{}–100\hspace{0.5em}\mathrm{zs})$ derived from earlier neutron measurements in fusion-fission reactions. The importance of such effects in the population of nuclei in the heavy and superheavy mass regions by transfer reactions is discussed.

We study the breakup of one-neutron halo nuclei in the Coulomb field of a target nucleus. In the post-form distorted wave Born approximation theory of this reaction, with only Coulomb distortions in the entrance and outgoing channels, an analytic solution for the breakup T matrix is known. We study this T matrix and the corresponding cross sections numerically. This formula can be related to the first order semiclassical treatment of the electromagnetic dissociation. This theory contains the electromagnetic interaction between the core and the target nucleus to all orders. We show that higher order effects (including postacceleration) are small in the case of higher beam energies and forward scattering. We investigate the beam energy dependence of the postacceleration effects. They are found to be quite important for smaller beam energies (slow collisions), but almost negligible at larger ones.

We have measured production cross sections of projectilelike fragments in the reaction of neutron-deficient ${}^{112}\mathrm{Sn}$ with a ${}^9\mathrm{Be}$ target at an energy of $E_{\mathrm{lab}}=1A\hspace{0.5em}\mathrm{GeV}.$ Results have been obtained for neutron-deficient products along the $N=Z$ line down to the subnanobarn range. We find very good agreement with the recently revised empirical parametrization EPAX. In addition, a few one- and two-proton pickup cross sections have been measured. The former ones are well reproduced by intranuclear-cascade calculations.

Using an expanding matter model with a Lennard-Jones potential, the instability of the expanding system is investigated. The pressure, temperature, and density fluctuations are calculated as functions of density during the time evolution of the expanding matter, which are compared to the coexistence curve calculated by the Gibbs ensemble. The expanding matter undergoes the first order phase transition in the limit of the quasistatic expansion. The resultant fragment mass distributions are also investigated.

The leading order nonrelativistic QCD result for the quarkonium-hadron interaction cross section is derived by using the QCD factorization formula combined with the Bethe-Salpeter amplitude for the heavy quark bound state. Our result shows the equivalence of this approach with the operator product expansion even for the bound state scattering to leading order in QCD. We also apply the formula to the charmonium system and investigate the relativistic correction coming from the phase space of the reaction. We find that although $J/\psi$-gluon cross section gets a large relativistic correction at higher energies, the correction becomes small in the $J/\psi$-hadron cross section due to the increase of the gluon distribution at smaller x inside the hadron.

Event-by-event fluctuations in the multiplicities of charged particles and photons, and the total transverse energy in $158A\hspace{0.5em}\mathrm{GeV}$ Pb+Pb collisions are studied for a wide range of centralities. For narrow centrality bins the multiplicity and transverse energy distributions are found to be near perfect Gaussians. The effect of detector acceptance on the multiplicity fluctuations has been studied and demonstrated to follow statistical considerations. The centrality dependence of the charged particle multiplicity fluctuations in the measured data has been found to agree reasonably well with those obtained from a participant model. However, for photons the multiplicity fluctuations have been found to be lower compared to those obtained from a participant model. The multiplicity and transverse energy fluctuations have also been compared to those obtained from the VENUS event generator.

A systematic analysis of multifragmentation (MF) in fully reconstructed events from $1A\mathrm{GeV}$ Au, La, and Kr collisions with C has been performed. These data are used to provide a definitive test of the variable volume version of the statistical multifragmentation model (SMM). A single set of SMM parameters directly determined by the data and the semi-empirical mass formula are used after the adjustable inverse level density parameter ${\epsilon }_0$ is determined by the fragment distributions. The results from SMM for second stage multiplicity, size of the biggest fragment, and the intermediate mass fragments are in excellent agreement with the data. Multifragmentation thresholds have been obtained for all three systems using SMM prior to secondary decay. The data indicate that both thermal excitation energy $E_{\mathrm{th}}^{*}$ and the isotope ratio temperature $T_{\mathrm{H}\mathrm{e}-\mathrm{D}\mathrm{T}}$ decrease with increase in system size at the critical point. The breakup temperature obtained from SMM also shows the same trend as seen in the data. The SMM model is used to study the nature of the MF phase transition. The caloric curve for Kr exhibits back-bending (finite latent heat) while the caloric curves for Au and La are consistent with a continuous phase transition (nearly zero latent heat) and the values of the critical exponents τ, β, and γ, both from data and SMM, are close to those for a “liquid-gas” system for Au and La. We conclude that the larger Coulomb expansion energy in Au and La reduces the latent heat required for MF and changes the nature of the phase transition. Thus the Coulomb energy plays a major role in nuclear MF.

The doubly odd nucleus ${}^{128}\mathrm{Pr}$ was studied via in-beam γ-ray spectroscopy using the ${}^{40}\mathrm{Ca}{+}^{92}\mathrm{Mo}$ reaction at 190 MeV. Five rotational bands were observed and assigned to configurations involving proton and neutron orbitals close to the Fermi level. The observed bands are discussed in the framework of the three-dimensional (3D) tilted axis cranking (TAC) model. Two of the negative-parity bands have almost degenerate energy levels, which suggests an interpretation in terms of the pseudospin doublet $\left[32̃1\right].$ It was impossible, however, to reproduce the observed small level spacing by either 3D TAC or two-quasiparticle–rotor model calculations.

Two-photon production in $\mathrm{pp}$ scattering is proposed as a means of studying virtual-pion emission. Such a process is complementary to real-pion emission in $\mathrm{pp}$ scattering. The virtual-pion signal is embedded in a background of double-photon bremsstrahlung. We have developed a model to describe this background process and show that in certain parts of phase space the virtual-pion signal gives significant contributions. In addition, through interference with the two-photon bremsstrahlung background, one can determine the relative phase of the virtual-pion process.

We investigate the effects of the spin-isospin channel of the Skyrme energy functional on predictions for Gamow-Teller distributions and superdeformed rotational bands. We use the generalized Skyrme interaction ${\mathrm{SkO}}^{\prime }$ to describe even-even ground states and then analyze the effects of time-odd spin-isospin couplings, first term by term and then together via linear regression. Some terms affect the strength and energy of the Gamow-Teller resonance in finite nuclei without altering the Landau parameter $g_0^{\prime }$ that to leading order determines spin-isospin properties of nuclear matter. Though the existing data are not sufficient to uniquely determine all the spin-isospin couplings, we are able to fit them locally. Altering these coupling constants does not change the quality with which the Skyrme functional describes rotational bands.

The potential energy surfaces are calculated for $N=Z,$ ${}^{72}\mathrm{Kr}$ to ${}^{92}\mathrm{Pd}$ nuclei in an axially deformed relativistic mean field approach, using a quadratic constraint scheme. The NL3 and TM1 parameter sets are used to see the dependence of our results on force parameters for a wide range of quadrupole deformation. The ground-state solutions as well as some excited state solutions for the binding energies and quadrupole deformations are deduced. Interestingly enough, more than two shapes at about the same binding energy are found to exist for all the $N=Z$ nuclei, which is perhaps the reason for a drastic change of shape with the addition of only two protons or two neutrons in the mass region $A\approx 80\pm 10.$ This new result of multiple low-lying spherical or deformed states, suggesting a “dynamically” variable nature of nuclear shapes in the neutron-deficient $N=Z$ exotic nuclei, needs an immediate experimental verification. For the ground state, our calculated results compare nicely with the experimental data and other theoretical works, wherever available.

We discuss charmonium production in proton-nucleus collisions at the Relativistic Heavy Ion Collider (RHIC) energies under the assumption of $x_F$ and $x_2$ scalings. We find that all the ambiguities due to energy loss are gone at this energy, and therefore data will reveal the scaling law, if any. These $p-A$ data will also be crucial to interpret nucleus-nucleus data with respect to a possible formation of a quark gluon plasma because the extrapolations for charmonium production from the present $p-A$ data to RHIC energies, based on the two scaling laws, differ by a factor of 4.

A light front formalism for deep inelastic lepton scattering from finite nuclei is developed. In particular, the nucleon plus momentum distribution and a finite system analog of the Hugenholtz–van Hove theorem are presented. Using a relativistic mean field model, numerical results for the plus momentum distribution and ratio of bound to free nucleon structure functions for oxygen, calcium, and lead are given. We show that we can incorporate light front physics with excellent accuracy while using easily computed equal time wave functions. Assuming nucleon structure is not modified in-medium we find that the calculations are not consistent with the binding effect apparent in the data not only in the magnitude of the effect, but also in the dependence on the number of nucleons.

We present a measurement of the half-life of ${}^{121}{\mathrm{Sn}}^m,$ obtaining a value of $43.9\pm 0.5\mathrm{yr}.$ In the same experiment, we measured a half-life of $21.8\pm 0.3\mathrm{yr}$ for ${}^{210}\mathrm{Pb}$ to verify the reliable performance of our data acquisition system and analysis methods. Our experimental ${}^{121}{\mathrm{Sn}}^m$ half-life is consistent with 49 yr, a value predicted on the basis of the systematic trend of the M4 isomeric γ-ray transition in ${}^{117}\mathrm{Sn}$ and ${}^{119}\mathrm{Sn}.$

The Faddeev-Yakubovsky equations for the α particle are solved. Accurate results are obtained for several modern nucleon-nucleon $\mathrm{}\left(\mathrm{NN}\right)\mathrm{}$ interaction models, which include charge-symmetry breaking effects in the $\mathrm{NN}$ force, nucleon mass dependences as well as the Coulomb interaction. These models are augmented by three-nucleon forces of different types and adjusted to the $3N$ binding energy. Our results are close to the experimental binding energy with a slight overbinding. Thus there is only little room left for the contribution of possible $4N$ interactions to the α-particle binding energy. We also discuss model dependences of the binding energies and the wave functions.

We compute the rates of real and virtual photon (dilepton) emission from dense QCD matter in the color-flavor locked (CFL) phase, focusing on results at moderate densities (three to five times the nuclear saturation density) and temperatures $T\simeq 80\hspace{0.5em}\mathrm{MeV}.$ We pursue two approaches to evaluate the electromagnetic response of the CFL ground state: (i) a direct evaluation of the photon self-energy using quark particle/hole degrees of freedom and (ii) a hidden local symmetry framework based on generalized mesonic excitations, where the $\rho$ meson is introduced as a gauge boson of a local SU(3) color-flavor group. The $\rho$ coupling to generalized two-pion states induces a finite width and allows us to address the issue of vector meson dominance in the CFL phase. We compare the calculated emissivities (dilepton rates) to those arising from standard hadronic approaches including in-medium effects. For rather large superconducting gaps (several tens of MeV at moderate densities), as suggested by both perturbative and nonperturbative estimates, the dilepton rates from CFL quark matter turn out to be very similar to those obtained in hadronic many-body calculations, especially for invariant masses above $M\simeq 0.3\hspace{0.5em}\mathrm{GeV}.$ A similar observation holds for (real) photon production.

The widths for one- and two-proton decay of the $1_2^{-}$ state in ${}^{18}\mathrm{Ne}$ are calculated. Shell-model wave functions are used to obtain the spectroscopic factors. The R-matrix theory of Barker which incorporates the final-state interaction between the two protons is used for the di-proton decay model. The calculated widths for both one- and two-proton decay are in qualitative agreement with experiment. We find that the decay width for sequential two-proton decay through the ghost of the ${1/2}^{+}$ bound state in ${}^{17}\mathrm{F}$ is comparable to the width of the direct di-proton decay.

Twenty four and twenty two new excited states are proposed in neutron-rich ${}^{115,117}\mathrm{Ag},$ respectively. These new results came from new works in Gammasphere measuring $>~$ triple- and higher-fold prompt coincidences following the spontaneous fission of ${}^{252}\mathrm{Cf}.$ The $\pi 7/2\left[413\right]$ rotational bands are identified in ${}^{115,117}\mathrm{Ag},$ along with higher bands of uncertain structures. A doublet structure in some bands is suggestive of softness toward triaxiality.