We discuss the properties of two distinct forms of hypothetical strange matter, small lumps of strange quark matter (strangelets) and of hyperon matter [metastable exotic multihypernuclear objects (MEMO’s)], with special emphasis on their relevance for present and future heavy ion experiments. The masses of small strangelets up to $A_B=40\mathrm{}$ are calculated using the MIT bag model with shell mode filling for various bag parameters. The strangelets are checked for possible strong and weak hadronic decays, also taking into account multiple hadron decays. It is found that strangelets which are stable against strong decay are most likely highly negatively charged, contrary to previous findings. Strangelets can be stable against weak hadronic decay but their masses and charges are still rather high. This has serious impact on the present high sensitivity searches in heavy ion experiments at the AGS and CERN facilities. On the other hand, highly charged MEMO’s are predicted on the basis of an extended relativistic mean-field model. Those objects could be detected in future experiments searching for short-lived, rare composites. It is demonstrated that future experiments can be sensitive to a much wider variety of strangelets.

The effect of medium-induced parton energy loss on jet fragmentation is studied in high-energy heavy-ion collisions. It is shown that an effective jet fragmentation function can be extracted from the inclusive $p_T$ spectrum of charged particles in the opposite direction of a tagged direct photon with a fixed transverse energy. We study the modification of the effective jet fragmentation function due to parton energy loss in $\mathrm{AA}$ as compared to $\mathrm{pp}$ collisions, including $E_T$ smearing from initial-state radiations for the photon-tagged jets. The effective fragmentation function at ${z=p}_T{/E}_T^{\gamma }\sim 1$ in $\mathrm{pA}$ collisions is shown to be sensitive to the additional $E_T$ smearing due to initial multiple parton scatterings whose effect must be subtracted out in $\mathrm{AA}$ collisions in order to extract the effective parton energy loss. Jet quenching in deeply inelastic lepton-nucleus scatterings as a measure of the parton energy loss in cold nuclear matter is also discussed. We also comment on the experimental feasibilities of the proposed study at the Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies and some alternative measurements such as using $Z^0$ as a tag at the LHC energy.

The recoil shadow method for the detection of fission fragments has been used to investigate delayed fission of very heavy Λ hypernuclei produced in the $p$-U interaction at the projectile energy of 1.5 GeV. From the measured distribution of delayed fission events in the shadow region and the calculated momenta of hypernuclei leaving the target the lifetime of the Λ hyperon in very heavy hypernuclei was determined to be $\tau =2.40\mathrm{}\pm 60$ ps. The comparison of the number of delayed fission events with that of the prompt events leads to an estimation of the cross section for the production of Λ hypernuclei in $p+$U collisions at 1.5 GeV of ${\sigma }_{\mathrm{Hy}}{=150\mathrm{}}_{-80}^{+150\mathrm{}}$ μb.

The nucleon’s strange-quark vector current form factors are studied from the perspective of chiral symmetry. It is argued that chiral perturbation theory cannot yield a prediction for the strangeness radius and magnetic moment. Arrival at definite predictions requires the introduction of additional, model-dependent assumptions which go beyond the framework of chiral perturbation theory. A variety of such model predictions is surveyed, and the credibility of each is evaluated.

A recent analysis by Törnqvist and Roos suggests that the σ meson has a mass of 860 MeV with a width of 880 MeV. In this work we calculate the properties of the σ meson using a generalized Nambu–Jona-Lasinio model that includes a model of confinement. We describe, in some detail, how the σ coupling to states in the two-pion continuum may be calculated, when using a Lorentz-vector confining interaction. As part of our work we provide a general procedure for calculating various loop diagrams in Minkowski momentum space for quarks in the presence of the confining interaction. We study the properties of the σ meson by considering $t$-channel scalar-isoscalar exchange between two quarks. The resulting quark-quark $T$ matrix $t_{\mathrm{qq}}{(q}^2)$ has $\mathrm{Re}{t}_{\mathrm{qq}}{(q}^2)=0\mathrm{}$ for $q^2=(0.823\mathrm{}\mathrm{GeV}{)}^2.$ Thus, we have $m_{\sigma }=0.823\mathrm{}\mathrm{GeV}.$ However, the coupling of the σ to the two-pion states is so large as to make $|t_{\mathrm{qq}}{(q}^2)|$ a rather smooth function over a broad range of $q^2.$ Therefore, we do not attempt to assign a width for the resonance.

We use QCD sum rules for the three-point function of a pseudoscalar and two nucleonic currents in order to estimate the charge dependence of the pion-nucleon coupling constant $g_{\mathrm{NN}\pi }$ coming from isospin violation in the strong interaction. The effect can be attributed primarily to the difference of the quark condensates $〈ūu〉$ and $〈\mathrm{d¯}d〉$. For the splitting ${(g}_{\mathrm{pp}{\pi }_0}-g_{\mathrm{nn}{\pi }_0}{)/g}_{\mathrm{NN}\pi }$ we obtain an interval of $1.2\times {10}^{-2}$ to $3.7\times {10}^{-2}$, the uncertainties coming mainly from the input parameters. The charged pion nucleon coupling is found to be the average of $g_{\mathrm{pp}{\pi }_0}$ and $g_{\mathrm{nn}{\pi }_0}$. Electromagnetic effects are not included.

We calculate perturbatively the effect of density on hadronic properties using the chiral quark model implemented by the QCD trace anomaly to see the possibility of constructing a Lorentz-invariant Lagrangian at finite density. We calculate the density-dependent masses of the constituent quark, the scalar field, and the pion in one-loop order using the technique of thermofield dynamics. In the chiral limit, the pion remains massless at finite density. It is found that the tadpole-type corrections lead to decreasing masses with increasing baryon density, while the radiative corrections induce Lorentz-symmetry-breaking terms. We found in the large $N_c$ limit with large scalar mass that the tadpoles dominate and the mean-field approximation is reliable, giving rise to a Lorentz-invariant Lagrangian with masses decreasing as the baryon density increases.

Helicity amplitudes for the ${\gamma }^{*}N\to \Delta$ transition are calculated using the cloudy bag model. A correction for center-of-mass motion is carried out using a modified Peierls-Thouless projection method. This reduces the magnitude of the transition amplitudes at small momentum transfers and enhances them at modest momentum transfers. Our calculation shows that the pion cloud contributes substantially to the transition helicity amplitudes, with the final result giving reasonable agreement with the corresponding experimental values.

We study the deuteron electrodisintegration with inclusion of the neutral currents focusing on the helicity asymmetry of the exclusive cross section in coplanar geometry $\mathcal{A}\left({\vartheta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}\right)$. We stress that a measurement of $\mathcal{A}\left({\vartheta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}\right)$ in the quasielastic region is of interest for an experimental determination of the weak form factors of the nucleon, allowing one to obtain the parity-violating electron neutron asymmetry. Numerically, we consider the reaction at low-momentum transfer and discuss the sensitivity of $\mathcal{A}\left({\vartheta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}\right)$ to the strangeness radius and magnetic moment. The problems coming from the finite angular acceptance of the spectrometers are also considered.

The proton capture cross sections of the stable molybdenum isotopes 92, 94, 95, and 98 have been measured by means of the activation method in the proton energy range between 1.5 and 3 MeV. Thin layers of natural molybdenum were irradiated at the Karlsruhe 3.75 MV Van de Graaff accelerator with proton beams of 20–55 $\mu$A. The activity induced by ($p,\gamma )$ reactions was measured with a calibrated HPGe detector. In this way, six cross sections for populating ground states and isomers in four different Tc isotopes could be determined simultaneously. The systematic uncertainties of this method are typically 4%. The fact that the resulting cross sections are 2–4 times larger than recent statistical model predictions illustrates the need of experimental data for the yet unexplored field of $(p$,$\gamma )$ reactions in the mass region beyond $A=90\mathrm{}$. The present results are important for a quantitative discussion of the production of the abundant $p$ nuclei ${}^{92}$Mo, ${}^{94}$Mo, ${}^{96}$Ru, and ${}^{98}$Ru during SN Ia explosions. They represent also a first step in establishing parameter systematics that allow for more reliable model extrapolations into the region of unstable nuclei of relevance for the $p$ process in SN II.

Using the full temperature-dependent extended Thomas-Fermi formalism, we calculate the equation of state of inhomogeneous nuclear matter for a force that has been fitted to essentially all nuclear masses, and has the correct properties of neutron matter. Both droplet and bubble phases are considered, under the conditions appropriate to a collapsing star. We examine the relevance of the choice of effective mass to the temperature.

A disagreement between two determinations of ${\Gamma }_{\alpha }$ of the astrophysically relevant level at $E_x$=4.378 MeV in ${}^{19}$F has been stated in two recent papers by Wilmes et al. and de Oliveira et al. In this work the uncertainties of both papers are discussed in detail, and we adopt the value ${\Gamma }_{\alpha }$ = ${(1.5\mathrm{}}_{-0.8}^{+1.5\mathrm{}})$$\times {10}^{-9}\hspace{0.5em}$ eV for the 4.378 MeV state. In addition, the validity and the uncertainties of the usual approximations for mirror nuclei ${\Gamma }_{\gamma }{(}^{19}\mathrm{F}\left)\approx {\Gamma }_{\gamma }{(}^{19}\mathrm{Ne}\right),\hspace{0.5em}{\theta }_{\alpha }^2{(}^{19}\mathrm{F}\left)\approx {\theta }_{\alpha }^2{(}^{19}\mathrm{Ne}\right)$ are discussed, together with the resulting uncertainties on the resonance strengths in ${}^{19}$Ne and on the ${}^{15}\mathrm{O}(\alpha ,\gamma {)}^{19}$Ne rate.

Spectroscopic factors of six low-lying neutron hole states in ${}^{207}\mathrm{Pb}$ were measured with a $\mathrm{}(p,d)\mathrm{}$ reaction at 65 MeV. The results are compared with previous $\mathrm{}(p,d)\mathrm{}$ reaction data as well as recent escape width ones of isobaric analog states in ${}^{208}\mathrm{Bi}$ into the neutron hole states in ${}^{207}\mathrm{Pb}.$ The spectroscopic factor for the ${2f}_{7/2}$ hole state shows a strong quenching (about 50% of the sum-rule limit), which suggests the existence of considerable strengths in higher excitation energy region. The appearance of the fragmentation or quenching in neutron hole strength distribution observed in the $2p-1f$ and $3p-2f$ shell regions is discussed.

Fusion cross section measurements for the ${}^{16,18}\mathrm{O}{+}^{58,60,64}\mathrm{Ni}$ systems, in the energy range $38<~E_{\mathrm{lab}}<~64$ MeV are presented. The standard radius deviations obtained from the data analysis, considering the zero-point motion of the nuclear surface, are compared to those associated to quadrupole and pairing vibration modes. Using the optical model analysis of the elastic data, the connection between the threshold anomaly and the subbarrier fusion enhancement is investigated.

The effective running coupling constants in the Walecka model are investigated by introducing renormalization-group equations at finite density, where couplings are divided into two parts: density dependence and momentum dependence. The results are applied to one-loop calculations in nuclear matter.

A collective contribution to backbending at high spin states in the interacting boson model (IBM) is found. The condition for the collective backbending in the IBM is the existence of an attractive force between the $d$ bosons and the finiteness of the boson number. An application to ${}^{136}$Nd is presented.

We find that a spin-orbit force with the conventional Skyrme form reproduces satisfactorily the isospin dependence of the spin-orbit field generated in relativistic Hartree calculations on semi-infinite nuclear matter with different neutron excesses. We also examine a generalization of the Skyrme-type energy-density functional that leads to still better agreement with the relativistic Hartree calculations.

The well known experimental levels of ${}^{208}$Bi have been calculated with a generalized intermediate coupling model with Gaussian potential with and without an octupole phonon interaction parameter. The neutron-proton interaction parameters are taken from those obtained in the calculation of 34 experimental levels in ${}^{210}$Bi. The goodness of fit of the calculated energies to the energies of the 36 experimentally assigned states in ${}^{208}$Bi is quite remarkable in spite of the fact that the neutron-proton interaction parameters have been transferred from fitting in ${}^{210}$Bi, a neutron shell away. Finally, the calculated levels of ${}^{208}$Bi are compared with those calculated by a delta force.

The collapse of structure effects observed in hot nuclei is interpreted in terms of a dynamic lattice model which describes the process of nucleon (clusters) evaporation from a hot nucleus, predicting the final mass distribution. Results are compared with experimental data for the ${}^{10}{\mathrm{B}+}^9\mathrm{Be}$ and ${}^{10}{\mathrm{B}+}^{10}\mathrm{B}$ reactions, and indicate that the structures observed in the low-energy mass distributions in both simulation and experiment are a consequence of the competition between the residual interactions and the thermalization dissipative process. As a characteristic feature of complex evolving systems, this competition leads to long term memory during the dissipative path, the observables becoming thus insensitive to the actual microscopic interactions.