A calculation of thermal gluon decay shows that this process contributes significantly to strangeness production in a quark-gluon plasma. Our analysis does not support recent claims that this is the dominant process. In our calculations we take into account the resummed form of the transverse and longitudinal parts of the gluon propagator following the Braaten-Pisarski method. The estimate of the damping rate entering the effective gluon propagator subjects our results to uncertainty.

Effects of N¯N polarization on vector meson (ρ and ω) masses at finite temperature are studied. Including a reduced nucleon mass in a hot matter, we find that the reduction of vector meson masses due to the vacuum effect is larger than the increase of their masses from interactions with nucleons and pions in the hot matter. The vector meson masses at finite temperature thus decrease with temperature.

The level structure of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Na}$ above the proton threshold has been investigated in the past by charge exchange reactions and by the resonant scattering of a radioactive ${}_{}{}^{19}{}_{}{}^{}\mathrm{Ne}$ beam on a hydrogen target. A discrepancy was found between the two sets of experiments for the excitation energy of the state at ≊3050 keV, which led to discussions about systematic deviations in the results of the different methods. We have reanalyzed the data of one of the ${(}^3$He,t) experiments and find an agreement with the results of the scattering experiment.

The suggestion made recently by H. Abele et al. that relativistic effects in the interaction of alpha particles with various nuclei at intermediate energies may remove the existing discrepancy between the theoretical predictions and the experimental data for the reaction cross section is investigated. We use a relativistic model based on the Kemmer-Duffin-Petiau equation and find that relativistic effects do not lead to a reduction in the reaction cross section within the present approach. Alternative explanations are discussed.

We investigate the specific heat of superfluid neutrons in the region of the crust of a neutron star characterized by unusual nuclear shapes, whose possible existence has been recently proposed. To describe pairing properties the results from Reid soft-core potential for nucleon-nucleon interaction are used. It is found that the presence of unusual nuclei causes a sizable increase in the specific heat. The results can have consequences in the study of thermal evolution of young neutron stars.

We suggest that there might be a production of a large number of glueballs in relativistic nucleus-nucleus collisions if the quark-gluon plasma (QGP) phase is realized. The ratio of the number of the produced glueball to that of the neutral pions directly produced in the process of QGP hadronization is estimated phenomenologically. Being a function of the phase transition temperature and chemical potential, it can be as large as a few percents. Considering the fact that the hadronization is very complicated, we anticipate that the abundant population of glueballs from the quark-gluon plasma at least may exert influences on the final-state ${\mathit{K}}^{+}$/${\mathrm{\pi }}^{+}$ ratio.

We show that the 1/${\mathit{N}}_{\mathit{c}}$ rotational corrections of ${\mathit{g}}_{\mathit{A}}$, derived using the semiclassical quantization scheme in the Nambu–Jona-Lasino model, possess correct properties under charge conjugation.

Dilepton production from ${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$ annihilation in nuclear matter is calculated in a simple two-level Delta-hole model and a more realistic model including both real pions and nucleon-hole and Delta-hole excitations. Substantial enhancement of the dilepton yield is found in the invariant mass region M<250 MeV/${\mathit{c}}^2$ due to annihilation of noncollective low-energy high-momentum nucleon-hole modes having a (very) small pion component. The inclusion of a finite temperature in the dispersion relation does not affect the total dilepton yield much, although it causes significant redistribution of the contributions from the various combinations of pionic modes.

The superdeformed bands in the A∼150 region are studied with the cranking Bohr-Mottelson Hamiltonian proposed by us. The transition energies can be represented satisfactorily and the level spins are extracted. The validity of our formulas and the reliability of the spin determinations are discussed.

Helicity amplitudes for the electroproduction of the ${\mathit{N}}^{\mathrm{*}}$(1535) from the nucleon are calculated in a constituent quark model formulated in light front dynamics. Previous work is extended and improved.

We calculate the differential cross section, photon asymmetry, and initial deuteron polarizations of the reaction γd→${\mathrm{\pi }}^0$d in the energy region from threshold up to 1 GeV. We compare our results with available data and give predictions where no data are available. The calculation is performed fully relativistically, by applying the spectator-on-mass-shell prescription to the single- and double-scattering diagrams. We study the sensitivity of this reaction to the use of pseudovector versus pseudoscalar πNN couplings when the elementary γN→πN reaction takes place on a bound nucleon.

We have excited the giant resonance region in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ via inelastic electron scattering, and have measured the first complete angular correlations for charged particle emission for this reaction for four values of momentum transfer ranging from 0.24 ${\mathrm{fm}}^{\mathrm{-}1}$ to 0.61 ${\mathrm{fm}}^{\mathrm{-}1}$. By analyzing the α-emission channels via the Legendre and resonance formalisms, we unambiguously determined the multipole contributions to the total cross section for α emission to the ground state of ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$, and have set limits on these contributions for α emission to the first excited state of ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$. We have found that, in both cases, E2 radiation is the strongest contribution but that E0 and E3 contributions cannot be ignored. By constructing total multipole form factors and fitting them within the distorted wave Born approximation using a transition charge density specified by the Tassie model, we deduced multipole transition strengths and fractions of the appropriate sum rules. Our results are compared with those from the (p,p’α) and (α,α’,α) reactions.

High-spin states in ${}_{}{}^{80}{}_{}{}^{}\mathrm{Kr}$ were studied using the ${}_{}{}^{65}{}_{}{}^{}\mathrm{Cu}$${(}^{18}$O,p2n) reaction at 65 MeV. Prompt γ-γ coincidences were measured using the Pitt-FSU detector array with nine high-purity Compton-suppressed Ge detectors and a 28-element Bismuth Germanate multiplicity filter. The previous level scheme has been extended by 16 new states up to spins and parities of ${20}^{+}$ and (${19}^{\mathrm{-}}$). The known band crossing in the positive-parity yrast band of ${}_{}{}^{80}{}_{}{}^{}\mathrm{Kr}$ near ħω≊0.5 MeV may be due to a ${\mathit{g}}_{9/2}$ neutron alignment, rather than a ${\mathit{g}}_{9/2}$ proton alignment as had been previously thought, based on the predicted oblate shape by Hartree-Fock-Bogolyubov calculations. No evidence was found for a second crossing in the yrast sequence up to ħω=0.9 MeV. The new extension of the ground-state band through nonyrast states points to another band crossing at ħω≊0.62 MeV which may be caused by a ${\mathit{g}}_{9/2}$ proton alignment. A new negative-parity high-spin band shows that rotational bands do form at excitations above the strongly mixed low-spin levels as in the isotone ${}_{}{}^{82}{}_{}{}^{}\mathrm{Sr}$.

An iron-free beta spectrometer with pre- and post-acceleration of electrons was used to study β branches and conversion electrons at very low energies in the β decay of ${}_{}{}^{228}{}_{}{}^{}\mathrm{Ra}$. Results of conversion-electron and γ-ray spectroscopy are analyzed using β selection rules and two-quasiparticle-rotor model considerations. A tentative ${}_{}{}^{228}{}_{}{}^{}\mathrm{Ac}$ level scheme, including model-dependent spin-parity and configuration assignments consistent with the available data, is presented.

Two new superdeformed (SD) bands have been observed in ${}_{}{}^{150}{}_{}{}^{}\mathrm{Tb}$ using the reaction ${}_{}{}^{31}{}_{}{}^{}\mathrm{P}$${+}^{124}$Sn and the GAMMASPHERE detector array. These new bands are interpreted as being excited SD configurations involving a proton and a neutron particle-hole excitation, respectively. The configurations are discussed in terms of the occupancy of high-N intruder orbitals. These data are used to provide information on (i) the contribution to the dynamic moments of inertia due to the occupation of specific orbitals, (ii) the deformation driving effects of the particle-hole states, and (iii) the consequences of these effects on pairing and band-crossings.

A superdeformed band has been found in ${}_{}{}^{142}{}_{}{}^{}\mathrm{Eu}$. It is populated with 1.2(2)% of the total γ-ray intensity that decayed into ${}_{}{}^{142}{}_{}{}^{}\mathrm{Eu}$ via the reaction ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$${(}^{27}$Al,5n${)}^{142}$Eu at 152 MeV. The strength of the band is similar to that previously reported in ${}_{}{}^{143}{}_{}{}^{}\mathrm{Eu}$, where the superdeformed band is populated with an intensity of 1.1(1)%. This is unexpected, since both total Routhian surface (TRS) and cranked modified oscillator (MO) calculations predict that the superdeformed band in ${}_{}{}^{143}{}_{}{}^{}\mathrm{Eu}$ becomes yrast at lower spin than that in ${}_{}{}^{142}{}_{}{}^{}\mathrm{Eu}$. This difference is ∼4ħ in the MO calculations and ∼8ħ in the TRS. Extrapolation of the ‘‘normal’’-deformed yrast states in ${}_{}{}^{143}{}_{}{}^{}\mathrm{Eu}$ shows, however, that a difference of ∼8ħ in spin corresponds to a change in the relative energy of the superdeformed and normal-deformed yrast lines of only ∼1 MeV.