The ${}_{\Lambda }^{13}\mathrm{C}$ hypernucleus was studied by measuring $\gamma$ rays in coincidence with the ${}^{13}\mathrm{C}{(K}^{-},{\pi }^{-})$ reaction. $\gamma$ rays from the ${1/2}^{-}$ and ${3/2}^{-}$ states, which are the partners of the spin-orbit doublet states with a predominant configuration of ${[}^{12}{\mathrm{C}}_{\mathrm{g}.\mathrm{s}.\mathrm{}}{(0\mathrm{}}^{+})\otimes p_{\Lambda }],$ to the ground state were measured. The splitting of the states was found to be $\Delta {E(1/2\mathrm{}}^{-}-{3/2}^{-})=+152\mathrm{}\pm 54(\mathrm{stat})\pm 36(\mathrm{syst})\hspace{0.5em}\mathrm{keV}.$ This value is 20–30 times smaller than that of single particle states in nuclei around this mass region. The $j_{\Lambda }={\mathcal{l}}_{\Lambda }-1/2\left[{(p}_{1/2}{)}_{\Lambda }\right]$ state appeared higher in energy, as in normal nuclei. The value gives new insight into the $\mathrm{YN}$ interaction. The excitation energies of the ${1/2}^{-}$ and ${3/2}^{-}$ states were obtained as $10.982\pm 0.031\left(\mathrm{stat}\right)\pm 0.056\left(\mathrm{syst}\right)$ and $10.830\pm 0.031\left(\mathrm{stat}\right)\pm 0.056\left(\mathrm{syst}\right)\hspace{0.5em}\mathrm{MeV},$ respectively. We also observed $\gamma$ rays from the ${3/2}^{+}$ state, which has a ${[}^{12}\mathrm{C}{(2\mathrm{}}^{+})\otimes s_{\Lambda }]$ configuration, to the ground state in ${}_{\Lambda }^{13}\mathrm{C}.$ The excitation energy of the ${3/2}^{+}$ state was obtained as $4.880\pm 0.010\left(\mathrm{stat}\right)\pm 0.017\left(\mathrm{syst}\right)\hspace{0.5em}\mathrm{MeV}.$ Nuclear $\gamma$ rays with energies of 4.438 and 15.100 MeV had similar yields, which suggests that a quasifree knockout of a $\Lambda$ particle is dominant in highly excited regions.

We consider a model where, for a finite disintegrating system, yields of composites can be calculated to arbitrary accuracy. An analytic answer for yields is also known in the thermodynamic limit. In the range of temperature and density considered in this work, the model has a phase transition. This phase transition is first order. The analytic expression for yields of composites, in the thermodynamic limit, does not conform to the expression $〈n_a〉{=a}^{-\tau }f\left(a^{\sigma }\right(T-T_c\left)\right)$ where the usual identification would be that $T_c$ is the critical temperature and $\tau ,\sigma$ are critical exponents. Nonetheless, for finite systems, we try to fit the yields with the above expression. A minimization procedure is adopted to get the parameters $T_c,\tau ,$ and $\sigma .$ While deviations from the formula are not negligible, one might believe that the deviations are consistent with the corrections attributable to finite particle number effects and might then conclude that one has deduced at least approximately the values of critical parameters. This exercise thus points to difficulties of trying to extract critical parameters from data on nuclear disintegration. An interesting result is that the value of $T_c$ deduced from the “best” fit is very close to the temperature at which the first order phase transition occurs in the model. The yields calculated in this model can also be fitted quite well by a parametrization derived from a droplet model.

Fusion cross sections have been measured for the symmetric system ${}^{46}\mathrm{Ti}{+}^{46}\mathrm{Ti}$ in the energy range encompassing the Coulomb barrier. A representation of the fusion barrier distribution has been obtained from the second energy derivative of the excitation function. The data are well described by coupled-channels calculations including two quadrupole phonons and one octupole phonon of both colliding nuclei. The comparison with previous data for ${}^{40}\mathrm{Ca}{+}^{46}\mathrm{Ti}$ and ${}^{40}\mathrm{Ca}{+}^{40}\mathrm{Ca}$ clarifies the relative importance of various low-lying inelastic exitations of ${}^{46}\mathrm{Ti}$ and of ${}^{40}\mathrm{Ca}$ in the subbarrier fusion yields. Similarities with the case of ${}^{58}\mathrm{Ni}{+}^{60}\mathrm{Ni}$ are pointed out.

Potentional energy surface calculations for the doubly midshell nucleus ${}_{66}^{170}{\mathrm{Dy}}_{104}$ support a variety of extreme properties. The ground-state deformation is among the largest in the region, consistent with it having the maximal value of valence particles for any nucleus below the ${}^{208}\mathrm{Pb}$ doubly closed shell. The energy minimum is found to be remarkably constant in the $({\beta }_2,\gamma )$ plane as a function of angular momentum. The nucleus is predicted to undergo a dual alignment with midshell high-$j$ protons and neutrons aligning simultaneously at spin $\approx 14ħ.$ Configuration-constrained calculations for the two-quasiparticle configurations predict the presence of a low-lying $K^{\pi }{=6\mathrm{}}^{+}$ state with a similar axially symmetric shape to the highly deformed ground state.

Head-on collisions of ${}^{16}\mathrm{O}{+}^{16}\mathrm{O}$ are calculated using an extended version of the time-dependent Hartree-Fock theory known as the time-dependent density-matrix theory (TDDM). TDDM deals with both one-body and two-body dissipation in a quantum-mechanical way. A newly developed TDDM code, which includes spin-orbit force in a mean field, is used. It is found that the threshold energy above which the colliding nuclei do not fuse increases due to two-body dissipation. Head-on collisions of ${}^{22}\mathrm{O}{+}^{22}\mathrm{O}$ are also calculated to investigate the effects of two-body collisions in exotic nuclei. In contrast to the case of ${}^{16}\mathrm{O}{+}^{16}\mathrm{O},$ no additional dissipation due to two-body collisions is found in the head-on collisions of ${}^{22}\mathrm{O}{+}^{22}\mathrm{O}.$

Pseudospin symmetry in nuclei is investigated by solving the Dirac equation with Woods-Saxon scalar and vector radial potentials, and studying the correlation of the energy splittings of pseudospin partners with the nuclear potential parameters. The pseudospin interaction is related to a pseudospin-orbit term that arises in a Schroedinger-like equation for the lower component of the Dirac spinor. We show that the contribution from this term to the energy splittings of pseudospin partners is large. The near pseudospin degeneracy results from a significant cancellation among the different terms in that equation, manifesting the dynamical character of this symmetry in the nucleus. We analyze the isospin dependence of the pseudospin symmetry and find that its dynamical character is behind the different pseudospin splittings observed in neutron and proton spectra of nuclei.

The g factors of the first $2^{+}$ states and the $B\left(E2\mathrm{}\right)\mathrm{}$ values of the ${(2\mathrm{}}_1^{+}\to 0_1^{+})$ transitions have been determined with high precision for all stable doubly even Zn isotopes employing the combined technique of projectile Coulomb excitation in inverse kinematics and transient magnetic fields. In addition, this systematic study was supplemented by a first measurement of radioactive ${}^{62}\mathrm{Zn}$ ${(T}_{1/2}=9.2\mathrm{}\hspace{0.5em}h)$ formed in an $\alpha$-transfer reaction with a ${}^{58}\mathrm{Ni}$ beam. The ${g(2\mathrm{}}_1^{+})$ values obtained are in good agreement with previous data but provide considerably higher accuracy. The same quality of agreement was found for the $B\left(E2\mathrm{}\right)\mathrm{}$ values with the exception of ${}^{70}\mathrm{Zn}$ where the measured value is slightly smaller. The experimental data were compared with large scale shell model calculations considering configurations in the $\mathrm{fp}$ and $\mathrm{fpg}$ model spaces with inert cores of ${}^{40}\mathrm{Ca}$ and ${}^{56}\mathrm{Ni},$ respectively.

Rotational bands have been found in ${}^{57}\mathrm{Co}$ using the ${}^{28}\mathrm{Si}{(}^{32}\mathrm{S},3p)$ reaction at 130 MeV. The bands, extending the mass 60 region of large deformation down to $Z=27,$ are signature-partner sequences. Their quadrupole moments are similar to those of bands in the neighboring nuclei. The features of the new bands are described by Skyrme Hartree-Fock calculations favoring a configuration assignment with one neutron and one proton excited in the respective ${1g}_{9/2}$ intruder orbital. An attempt to describe the magnetic $\mathrm{}\left(M1\mathrm{}\right)\mathrm{}$ properties of the signature-partner structure is also presented.

We examine three different ways a heavy quarkonium can dissociate at high temperatures. The heavy quarkonium can dissociate spontaneously when it becomes unbound at a temperature above its dissociation temperature. Following the recent work of Digal, Petreczky, and Satz, we calculate the dissociation temperatures of heavy quarkonia taking into account the angular momentum selection rules and using a temperature-dependent potential inferred from lattice gauge calculations. We find that the selection rules change the dissociation temperatures substantially for charmonia but only slightly for bottomia. A quarkonium system in thermal equilibrium with the medium can dissociate by thermalization. The fraction of quarkonium lying above the dissociation threshold increases as temperature increases. A quarkonium can also dissociate by colliding with light hadrons. We evaluate the cross sections for the dissociation of $J/\psi$ and ${\rm Y}$ in collision with $\pi$ as a function of the temperature of the hadron medium, using the quark-interchange model of Barnes and Swanson. We find that as the temperature increases, the threshold energy decreases and the dissociation cross section increases.

High-$p_T$ pion and kaon production is studied in relativistic proton-proton, proton-nucleus, and nucleus-nucleus collisions in a wide energy range. Cross sections are calculated based on perturbative QCD, augmented by a phenomenological transverse-momentum distribution of partons (“intrinsic $k_T”).\mathrm{}$ An energy dependent width of the transverse-momentum distribution is extracted from pion and charged hadron production data in proton-proton/proton-antiproton collisions. Effects of multiscattering and shadowing in the strongly interacting medium are taken into account. Enhancement of the transverse-momentum width is introduced and parameterized to explain the Cronin effect. In collisions between heavy nuclei, the model overpredicts central pion production cross sections (more significantly at higher energies), hinting at the presence of jet quenching. Predictions are made for proton-nucleus and nucleus-nucleus collisions at relativistic heavy ion collider energies.

The elliptic flow in heavy ion collisions at the Relativistic Heavy Ion Collider is studied in a multiphase transport model. By converting the strings in the high energy density regions into partons, we find that the final elliptic flow is sensitive to the parton scattering cross section. To reproduce the large elliptic flow observed in Au+Au collisions at $\sqrt{s}=130\mathrm{}\hspace{0.5em}A\mathrm{GeV}$ requires a parton scattering cross section of about 6 mb. We also study the dependence of the elliptic flow on the particle multiplicity, transverse momentum, and particle mass.

We report studies of the response of a massless particle confined by a potential. At large momentum transfer q it exhibits $\tilde{y}$ or equivalently Nachtmann ξ scaling, and acquires a constant width independent of q. This width has a contribution from the final state interactions of the struck particle, which persists in the |q$\overrightarrow{\mathrm{|}}$∞ limit. The width of the response predicted using the plane wave impulse approximation is smaller because of the neglect of final state interactions in that approximation. However, the exact response may be obtained by folding the approximate response with a function representing final state interaction effects. We also study the response obtained from the momentum distribution assuming that the particle is on the energy shell both before and after being struck. Quantitative results are presented for the special case of a linear confining potential. In this case the response predicted with the on-shell approximation has correct values for the total strength, mean energy, and width; however, its shape is wrong.

We study the S-wave interaction of mesons with baryons in the strangeness $S=0\mathrm{}$ sector in a coupled channel unitary approach. The basic dynamics is drawn from the lowest order meson-baryon chiral Lagrangians. Small modifications inspired by models with explicit vector meson exchange in the t channel are also considered. In addition the $\pi \pi N$ channel is included and shown to have an important repercussion in the results, particularly in the isospin 3/2 sector. The $N^{*}\mathrm{}\left(1535\right)\mathrm{}$ resonance is dynamically generated and appears as a pole in the second Riemann sheet with its mass, width, and branching ratios in fair agreement with experiment. A $\Delta \mathrm{}\left(1620\right)\mathrm{}$ resonance also appears as a pole at the right position although with a very large width, coming essentially from the coupling to the $\pi \pi N$ channel, in qualitative agreement with experiment.

Parity violating asymmetry in inclusive ${\pi }^0$ or ${\pi }^{+}$ meson production by longitudinally polarized electrons on unpolarized protons, is calculated as a function of the momentum transfer square $k^2$ and the total energy W of the $\pi N$ system. We consider the Δ contribution in the s channel, the standard Born contributions and the vector mesons (ρ and ω) exchanges in the t channel. The parity-odd term is the sum of two contributions. The main term (found to be linear in $k^2)$ comes from the isovector component of the electromagnetic currents. It is model independent and can be calculated exactly in terms of fundamental constants. The second term is isoscalar in nature. Near threshold and in the Δ region, it is found to be much smaller (in absolute value) than the isovector one.

The photo-induced depopulation of the quasistable isomer ${(t}_{1/2}>~1.2\times {10}^{15}\hspace{0.5em}\mathrm{yr})$ in ${}^{180}\mathrm{Ta}$ with angular momentum and parity $J^{\pi }{=9\mathrm{}}^{-}$ at an excitation energy $E_x=75\mathrm{}\hspace{0.5em}\mathrm{keV}$ was studied at the new bremsstrahlung irradiation facility installed at the Stuttgart 4.3 MV DYNAMITRON accelerator in the energy range of bremsstrahlung end point energies between $E_0=0.8\mathrm{}–3.1\hspace{0.5em}\mathrm{MeV}.$ The onset of the isomer depopulation could be observed starting at an end point energy of $E_0\approx 1\hspace{0.5em}\mathrm{MeV},$ i.e., at an intermediate state of ${}^{180}\mathrm{Ta}$ at or below that energy. Higher-lying intermediate states were found at 1.22, 1.43, 1.55, 1.85, 2.16, 2.40, 2.64, and 2.80 MeV. The extracted integrated cross sections show a remarkably strong depopulation of the ${}^{180}{\mathrm{Ta}}^m$ isomer by photoexcitation. The results are compared with previous experiments and recent quasiparticle-phonon model calculations. Implications of the results for a possible nucleosynthesis of ${}^{180}\mathrm{Ta}$ in the s process and the neutrino process are discussed.

We construct the equation of state (EOS) in a wide density range for neutron stars using the relativistic mean field theory. The properties of neutron star matter with both uniform and nonuniform distributions are studied consistently. The inclusion of hyperons considerably softens the EOS at high densities. The Thomas-Fermi approximation is used to describe the nonuniform matter, which is composed of a lattice of heavy nuclei. The phase transition from uniform matter to nonuniform matter occurs around $0.06\hspace{0.5em}{\mathrm{fm}}^{-3},$ and the free neutrons drip out of nuclei at about $2.4\times {10}^{-4}\hspace{0.5em}{\mathrm{fm}}^{-3}.$ We apply the resulting EOS to investigate the neutron star properties such as maximum mass and composition of neutron stars.

This new mass formula explains the shape of the binding energy versus neutron number curve of all the elements from Li to Bi. A simple comparison of the one-neutron separation energy versus neutron number curve with the experimental data clearly delineates positions of all the known old and new magic numbers, reveals extra stability at neutron number $N=16\mathrm{}$ $\mathrm{}(Z=7,8\mathrm{}),$ $N=14\mathrm{}$ $(Z=7\mathrm{}–10),$ $Z=14\mathrm{}$ $(N=13\mathrm{}-19),$ $N=6\mathrm{}$ $(Z=3\mathrm{}–8),$ and loss of magicity for nuclei with $N=8\mathrm{}$ $\mathrm{}(Z=4\mathrm{})\mathrm{}$ and $N=20\mathrm{}$ $(Z=12\mathrm{}–17).$ It supports existence of ${}^{32}\mathrm{Ne},$ ${}^{35}\mathrm{Na},$ ${}^{38}\mathrm{Mg},$ and ${}^{41}\mathrm{Al}$ nuclei as the last bound isotopes of Ne, Na, Mg, Al, and suggests ${}^{26}\mathrm{O}$ as a bound nucleus.

We report measurements of the cross section of the ${}^8\mathrm{Li}(d,\alpha {)}^6\mathrm{He}$ reaction in the energy range $E_{c.m.\mathrm{}}=2.3\mathrm{}–3.5\mathrm{MeV}$ using a ${}^8\mathrm{Li}$-radioactive beam on a ${\mathrm{CD}}_2$ foil. The astrophysical S factor and reaction rate were calculated from the measured cross section. The ${}^6\mathrm{He}$ nuclei produced in the reaction were detected in solid-state detector telescopes. This reaction might have affected the primordial abundance of ${}^6\mathrm{Li}$ in big bang nucleosynthesis, since ${}^6\mathrm{He}$ beta decays to ${}^6\mathrm{Li}.$ However, several big bang nucleosynthesis network calculations were found to be insensitive to this reaction, suggesting that the ${}^8\mathrm{Li}(d,\alpha {)}^6\mathrm{He}$ reaction does not affect ${}^6\mathrm{Li}$ primordial production.

A new $7\hspace{0.5em}\mu \mathrm{s}$ isomer in the drip line nucleus ${}^{140}\mathrm{Dy}$ was selected from the products of the ${}^{54}\mathrm{Fe}$ $(315\mathrm{}\hspace{0.5em}\mathrm{MeV}{)+}^{92}\mathrm{Mo}$ reaction by a recoil mass spectrometer and studied with recoil-delayed $\gamma -\gamma$ coincidences. Five cascading $\gamma$ transitions were interpreted as the decay of an $I^{\pi }{=8\mathrm{}}^{-}$ $\{\nu {9/2}^{-}\left[514\right]\otimes \nu {7/2}^{+}\left[404\right]\}$ K isomer $(T_{1/2}=7.0\mathrm{}(5\left)\mathrm{}\hspace{0.5em}\mu \mathrm{s}\right)$ via the ground-state band. The probability of proton emission from ${}^{141}\mathrm{Ho}$ to the $0^{+}$ ground state and to the $2^{+}$ excited state in ${}^{140}\mathrm{Dy}$ is discussed.

The $“2_1^{+}$ anomaly” in vibrational nuclei is studied in the context of alternate vibrational potentials. It is shown that a better reproduction of phonon and multiphonon multiplet energy centroids in vibrational nuclei is obtained with potentials having a strong quartic $\left(V\sim {\beta }^4\right)$ component.