The SU(3) extension of the linear sigma model is employed to elucidate the effect of including strangeness on the formation of disoriented chiral condensates. By means of a Hartree factorization, approximate dispersion relations for the 18 scalar and pseudoscalar meson species are derived and their self-consistent solution makes it possible to trace out the thermal path of the two order parameters as well as delineate the region of instability within which spontaneous pair creation becomes possible. The results depend significantly on the employed sigma mass, with the highest values yielding the largest regions of instability. An approximate solution of the equations of motion for the order parameter in scenarios emulating uniform scaling expansions show that even with a rapid quench only the pionic modes grow unstable. Nevertheless, the rapid and oscillatory relaxation of the order parameters leads to enhanced production of both pions and (to a lesser degree) kaons.

Chemically nonequilibrated quark-antiquark matter is studied within the Nambu–Jona-Lasinio model. The equations of state of nonstrange $\mathrm{}(q=u,d)\mathrm{}$ and strange $\mathrm{}(q=s)\mathrm{}\hspace{0.5em}q\overline{q}$ systems are calculated in the mean-field approximation. The existence of metastable bound states with zero pressure is predicted at finite densities and temperatures $T\lesssim 50\hspace{0.5em}\mathrm{MeV}.$ It is shown that the minimum energy per particle occurs for symmetric systems, with equal densities of quarks and antiquarks. At $T=0\mathrm{}$ these metastable states have quark number densities of about $0.5\hspace{0.5em}{\mathrm{fm}}^{-3}$ for $q=u,d$ and of $1\hspace{0.5em}{\mathrm{fm}}^{-3}$ for $q=s.\mathrm{}$ A first order chiral phase transition is found at finite densities and temperatures. The critical temperature for this phase transition is approximately 75 MeV (90 MeV) for the nonstrange (strange) baryon-free quark-antiquark matter. For realistic choices of parameters, the model does not predict a phase transition in chemically equilibrated systems. Possible decay channels of the metastable $q\overline{q}$ droplets and their signatures in relativistic heavy-ion collisions are discussed.

We discuss the Fermi-liquid properties of hadronic matter derived from a chiral Lagrangian field theory in which Brown-Rho (BR) scaling is incorporated. We identify the BR scaling as a contribution to Landau’s Fermi-liquid fixed-point quasiparticle parameter from “heavy” isoscalar meson degrees of freedom that are integrated out from a low-energy effective Lagrangian. We show that for the vector (convection) current, the result obtained in the chiral Lagrangian approach agrees precisely with that obtained in the semiphenomenological Landau-Migdal approach. This precise agreement allows one to determine the Landau parameter that enters in the effective nucleon mass in terms of the constant that characterizes BR scaling. When applied to the weak axial current, however, these two approaches differ in a subtle way. While the difference is small numerically, the chiral Lagrangian approach implements current algebra and low-energy theorems associated with the axial response that the Landau method misses and hence is expected to be more predictive.

For a nonrelativistic system we compare the Gersch-Rodriguez-Smith (GRS) and the impulse approximation (IA) approaches to the structure function. The first of these two approaches generates a series in $1/q,$ whereas the second treats the interaction between the struck and core nucleons perturbatively. Instead of the IA series we derive a DWIA representation and prove that, up to and including terms of order $\mathcal{O}{(1/q}^2),$ it is contained in the GRS series of the same order. This clarifies the relation between the two approaches and suggests that the two approaches, when treated exactly, produce identical structure function to arbitrary order in $1/q.$

Using a recently developed three-point formalism within the method of QCD sum rules we determine the vacuum susceptibilities needed in the two-point formalism for the coupling of axial, vector, tensor, and pseudoscalar currents to hadrons. All susceptibilities are determined by the space-time scale of condensates, which is estimated from data for deep inelastic scattering on nucleons.

A new chiral SU(3) Lagrangian is proposed to describe the properties of kaons and antikaons in the nuclear medium, the ground state of dense matter, and the kaon-nuclear interactions consistently. The saturation properties of nuclear matter are reproduced as well as the results of Dirac-Brückner theory. Our numerical results show that the kaon effective mass might be changed only moderately in the nuclear medium due to highly nonlinear density effects. After taking into account the coupling between the omega meson and the kaon, we obtain similar results for the effective kaon and antikaon energies as calculated in the one-boson-exchange model while in our model the parameters of the kaon-nuclear interactions are constrained by the SU(3) chiral symmetry.

The reaction $\nu \overrightarrow{d}{\mu }^{-}{\Delta }^{++}n$ is studied in the region of low $q^2$ to investigate the effect of deuteron structure and width of the $\Delta$ resonance on the differential cross section. The results are used to extract the axial vector $N-\Delta$ coupling $C_5^A$ from the experimental data on this reaction. The possibility to determine this coupling from electroweak interaction experiments with high intensity electron accelerators is discussed.

The positron decay partial half-life of ${}^{56}\mathrm{Ni}$ is needed to employ this isotope as a cosmic-ray chronometer. We conducted an experiment by counting a purified 2.8-$\mu \mathrm{Ci}$ source of ${}^{56}\mathrm{Ni}$ in GAMMASPHERE in order to search for the ${\beta }^{+}$-decay branch of this isotope. A plastic scintillator was used to measure the energy of positrons in coincidence with the positron-annihilation $\gamma$ rays and the characteristic 158-keV $\gamma$ ray line. A careful analysis of 96 h of source counting shows no net signal and results in an upper limit of 77 counts of 511-511-158 keV plus scintillator coincident events. From this result we establish a $1\sigma$ upper limit on the branch for this decay mode to be $(6.3\mathrm{}\times {10}^{-5})\%$. The discrepancy between the outcome of this experiment and previous measurements of this branch and the implications of this result for the ${}^{56}\mathrm{Ni}$ cosmic-ray chronometer problem are discussed.

The cross section of the ${}^{14}\mathrm{N}{\mathrm{}(n,p)\mathrm{}}^{14}\mathrm{C}$ reaction was measured at an astrophysically relevant energy using a newly constructed gas-scintillation drift chamber. Low-energy protons were detected with a good S/N value and a large acceptance of 4π, and scintillation photons emitted from He were detected to determine the neutron energy with a time-of-flight method. The cross section was obtained to be 1.67 (33) and 1.19 (14) mb at average neutron energies of 35.8 and 67.1 keV, respectively, and supports the values recently measured by a different method. The present study demonstrates the characteristic features of the chamber for studying a $\{n,p\left(\alpha \right)\}$ reaction of a gaseous sample using keV neutrons.

The reaction ${}^{18}\mathrm{Ne}(\alpha {,p)}^{21}\mathrm{Na},$ of importance to nuclear astrophysics, has been studied directly using the postaccelerated radioactive ${}^{18}\mathrm{Ne}$ beam available at Louvain-la-Neuve and a gaseous helium target. This study covered the energy region from 2.04 to 3.01 MeV in the center of mass, and identified various levels in the compound nucleus ${}^{22}\mathrm{Mg}.$ The stellar reaction rate due to these states has been deduced. The experimental rate shows good agreement with theoretical predictions [J. Görres, M. Wiescher, and F. K. Thielemann, Phys. Rev. C 51, 392 (1995)] above 2.5 GK.

The measurement of the neutron capture reaction ${}^{46}\mathrm{Ca}(n,\gamma {)}^{47}\mathrm{Ca}$ is of astrophysical interest, because ${}^{46}\mathrm{Ca}$ is bypassed by charged-particle reactions. The nucleus ${}^{46}\mathrm{Ca}$ is produced and destroyed by neutron-induced nucleosynthesis in hydrostatic helium, carbon, and neon burning through the reaction chain ${}^{45}\mathrm{Ca}(n,\gamma {)}^{46}\mathrm{Ca}(n,\gamma {)}^{47}\mathrm{Ca}.$ At the Karlsruhe and Tübingen 3.75 MV Van de Graaff accelerators the thermonuclear ${}^{46}\mathrm{Ca}(n,\gamma {)}^{47}\mathrm{Ca}(4.54\mathrm{}d)$ cross section was measured by the activation technique via the 1297.09 keV $\gamma$-ray line of the ${}^{47}\mathrm{Ca}$ decay. Samples of ${\mathrm{CaCO}}_3$ enriched in ${}^{46}\mathrm{Ca}$ by 5% were irradiated between two gold foils which served as capture standards using the ${}^7\mathrm{Li}\mathrm{}(p,n)\mathrm{}$ and $T(p,n)\mathrm{}$ reactions. The capture cross section was measured at the mean neutron energies 30, 104, 149, 180, and 215 keV, respectively. Maxwellian averaged capture cross sections were measured at the quasithermal neutron energies $kT=25\mathrm{}$ and 52 keV, respectively. It was found that the ${}^{46}\mathrm{Ca}(n,\gamma {)}^{47}\mathrm{Ca}$ cross section in the thermonuclear energy region and at thermal energy is dominated by an s-wave resonance at 28.4 keV with a neutron width ${\Gamma }_n{=(17.4\mathrm{}}_{-2.8}^{+3.6\mathrm{}})$ keV and a radiation width ${\Gamma }_{\gamma }=(2.4\mathrm{}\pm 0.3)$ eV. The stellar reaction rate is determined in the temperature range from $kT=1\mathrm{}$ to 250 keV and is compared with previous investigations using Hauser-Feshbach calculations or experimental cross section data. The astrophysical consequences of the new stellar reaction rate with respect to the nucleosynthetic abundance of ${}^{46}\mathrm{Ca}$ are discussed.

We present here useful relations showing the connection between the asymptotic normalization coefficient (ANC) and the fitting parameters in K- and R-matrix theory methods which are often used when analyzing low energy experimental data. It is shown that the ANC of a subthreshold bound state defines the normalization of both direct radiative capture leading to this state and resonance capture in which the state behaves like a subthreshold resonance. A determination of the appropriate ANC(s) thus offers an alternative method for finding the strength of these types of capture reactions, both of which are important in nuclear astrophysics.

Polarized protons were used to measure the analyzing power of $\mathrm{the}{}^9\mathrm{Be}(\overrightarrow{p},\gamma {)}^{10}\mathrm{B}$ reaction for $E_p=280\mathrm{}–0\hspace{0.5em}\mathrm{keV}.$ The analyzing power for the ground state transition compared to calculations leads to a spin-parity assignment of $2^{+}$ for the 7.478 MeV state of ${}^{10}\mathrm{B}.$ This $2^{+}$ assignment is consistent with other observables for this reaction and is predicted by cluster and shell model calculations. It is found that the $2^{+}$ assignment leads to a value for the astrophysical S factor for capture to the ground state of ${}^{10}\mathrm{B}$ of $S\left(0\right)=0.20\mathrm{}\hspace{0.5em}\mathrm{keV}\mathrm{}\mathrm{b}$ which is about 40% smaller than that obtained with a $2^{-}$ assignment.

We present the results of an experimental comparative study of the ${}^{40,48}\mathrm{Ca}$ resonance spectra between 6 and 12 MeV. The power of the heavy ion reaction ${}^{40,48}\mathrm{Ca}{(}^{86}\mathrm{Kr},{\hspace{0.5em}}^{86}{\mathrm{Kr}}^{\prime }{)}^{40,48}{\mathrm{Ca}}^{*}$ at 60 MeV per nucleon was exploited to enhance greatly the low energy part of inclusive spectra in order to look for the possible presence of a low energy dipole mode in ${}^{48}\mathrm{Ca}$ due to a neutron skin. We did not observe any difference in the $l=1\mathrm{}$ channel and therefore found no evidence of this mode. In the $l=2\mathrm{}$ channel, an important excess of strength was observed in ${}^{40}\mathrm{Ca}$ compared to ${}^{48}\mathrm{Ca}$.

The nuclide ${}^{262}\mathrm{Db}\hspace{0.5em}\mathrm{}(Z=105\mathrm{})\mathrm{}$ was produced in the reaction ${}^{248}\mathrm{Cm}{(}^{19}\mathrm{F},\hspace{0.5em}5n)$ at a beam energy of 106.5 MeV. ${}^{262}\mathrm{Db}$ was identified by observing four time correlated $\alpha$-$\alpha$ decay chains of ${}^{262}\mathrm{Db}$ and its daughter ${}^{258}\mathrm{Lr}$. From these correlations a production cross section of ${0.26}_{-0.09}^{+0.15\mathrm{}}$ nb was deduced. This cross section is more than one order of magnitude smaller than the peak cross section observed in the ${}^{249}\mathrm{Bk}{(}^{18}\mathrm{O},\hspace{0.5em}{5n)}^{262}\mathrm{Db}$ reaction. Model calculations with the HIVAP code gave good agreement with the cross section measured in the ${}^{19}\mathrm{F}{+}^{248}\mathrm{Cm}$ reaction.

Motivated by recent experimental observations, we discuss the freeze-out properties of the fireball created in central heavy ion collisions. We find that the freeze-out parameters, temperature T, and velocity gradient near the center of the fireball are similar for different colliding systems and beam energies. This means that the transverse flow is stronger in collisions of heavy nuclei than that of light ones.

We consider the masses used in recent studies involving the nonstrange sector of the $l=1\mathrm{}$ baryons. The use of T-matrix and K-matrix poles versus the conventional Breit-Wigner masses is discussed within the context of a large-$N_c$ fitting scheme.

We show that the fragment partitions and kinematic characteristics of fragments can change in the presence of an external Coulomb field at statistical multifragmentation of highly excited nuclei. There are indications that this effect takes place at intermediate energy peripheral nucleus-nucleus collisions. The phenomenon has general importance for understanding disintegration processes affected by long-range forces.

The results of relativistic mean field (RMF) calculations for the ground-state properties of odd-$A$ Bi isotopes are presented using the most successful nonlinear sets of Lagrangian parameters. The calculated quadrupole moments are found to increase as neutrons are added or removed from the $N=126\mathrm{}$ shell. However, no corresponding increase is revealed in the calculated charge radii. This observation is consistent with recent experimental findings.

The electric charge of strange quark matter is of vital importance to experiments. A recent investigation shows that strangelets are most likely highly negatively charged, rather than slightly positively charged as previously believed. Our present study indicates that negative charges can indeed lower the critical density, and thus be favorable to the experimental searches in heavy ion collisions. However, too much negative charges can make it impossible to maintain flavor equilibrium.