The density of accessible levels at low spin in the ( ${}^3\mathrm{He},\alpha \gamma$) reaction has been extracted for the ${}^{162}\mathrm{Dy}$, ${}^{166}\mathrm{Er}$, and ${}^{172}\mathrm{Yb}$ nuclei. The nuclear temperature is measured as a function of excitation energy in the region of 0–6 MeV. The temperature curves reveal structures indicating the onset of new degrees of freedom. The heat capacity of the nuclear system is discussed within the framework of a canonical ensemble.

In bombardment of ${}^{244}\mathrm{Pu}$ with ${}^{48}\mathrm{Ca}$, we observed a decay sequence consisting of an implanted heavy atom, three subsequent $\alpha$ decays, and a spontaneous fission (SF), all correlated in time and position. The measured $\alpha$ energies and corresponding time intervals were $E_{\alpha }=9.71\mathrm{}$ MeV ( $\Delta t=30.4\mathrm{}$ s), 8.67 MeV ( $\Delta t=15.4\mathrm{}$ min), and 8.83 MeV ( $\Delta t=1.6\mathrm{}$ min); for the SF ( $\Delta t=16.5\mathrm{}$ min), the total deposited energy was approximately 190 MeV. The $\alpha$-particle energies together with the decay times and SF terminating the chain offer evidence of the decay of nuclei with high atomic numbers. This decay chain is a good candidate for originating from the $\alpha$ decay of the parent nucleus ${}^{289}114$, produced with a cross section of about 1 pb.

We have measured the Coulomb dissociation of ${}^8\mathrm{B}$ into ${}^7\mathrm{Be}$ and a proton at 254 MeV/nucleon using a large-acceptance focusing spectrometer. The astrophysical $S_{17}$-factor for the ${}^7\mathrm{Be}(p,\gamma {)}^8\mathrm{B}$ reaction at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=0.25\mathrm{}–2.78\mathrm{MeV}$ is deduced yielding $S_{17}\left(0\right)=20.6\mathrm{}\pm 1.2$ (expt) $\pm 1.0\left(\mathrm{theor}\right)\mathrm{eV}\mathrm{b}$. This result agrees with the presently adopted zero-energy $S_{17}$-factor obtained in direct-reaction measurements and with the results of other Coulomb-dissociation studies performed at 46.5 and 51.2 MeV/nucleon.

We report on polarized beam–polarized target measurements of the spin-dependent neutron-proton total cross-section differences in longitudinal and transverse geometries ( $\Delta {\sigma }_L$ and $\Delta {\sigma }_T$, respectively) between $E_n=5\mathrm{}$ and 20 MeV. Single-parameter phase-shift analyses were performed to extract the phase-shift mixing parameter ${\varepsilon }_1$, which characterizes the strength of the nucleon-nucleon tensor interaction at low energies. Consistent with the trend of previous determinations at $E_n=25\mathrm{}$ and 50 MeV, our values for ${\varepsilon }_1$ imply a stronger tensor force than predicted by meson-exchange nucleon-nucleon potential models and nucleon-nucleon phase-shift analyses.

The virtual-bremsstrahlung yields in proton-proton scattering, $\mathrm{pp}\to {\mathrm{ppe}}^{+}{e}^{-}$, below the pion threshold were measured. The leptonic-angle dependence of the experimentally determined cross section is exploited in order to extract the nucleon-nucleon response functions in the timelike region. All six response functions are compared to the predictions of a microscopic, fully relativistic nucleon-nucleon model, as well as a model based on a low-energy-theorem expansion.

The proton elliptic flow in collisions of ${}^{48}\mathrm{Ca}$ on ${}^{48}\mathrm{Ca}$ at energies from 30 to 100 MeV/nucleon is studied in an isospin-dependent transport model. With increasing incident energy, the elliptic flow shows a transition from positive to negative flow. Its magnitude depends on both the nuclear equation of state (EOS) and the nucleon-nucleon scattering cross section. Different elliptic flows are obtained for a stiff EOS with free nucleon-nucleon cross sections and a soft EOS with reduced nucleon-nucleon cross sections, although both lead to vanishing in-plane transverse flow at the same balance energy.

Light charged particles emitted by the projectilelike fragment were measured in the direct and reverse collision of ${}^{93}$Nb and ${}^{116}$Sn at 25A MeV. The experimental multiplicities of hydrogen and helium particles as a function of the primary mass of the emitting fragment show evidence for a correlation with net mass transfer. The ratio of hydrogen and helium multiplicities points to a dependence of the angular momentum sharing on the net mass transfer.

A precise measurement of the ratios of the Drell-Yan cross section per nucleon for an 800 GeV/c proton beam incident on Be, Fe, and W targets is reported. The behavior of the Drell-Yan ratios at small target-parton momentum fraction is well described by an existing fit to the shadowing observed in deep-inelastic scattering. The cross-section ratios as a function of the incident-parton momentum fraction set tight limits on the energy loss of quarks passing through a cold nucleus.

Precision studies of the reaction ${}^3\mathrm{He}\left({e,e}^{\prime }p\right)$ using the three-spectrometer facility at the Mainz microtron MAMI are presented. All data are for quasielastic kinematics at $|\overrightarrow{q}|=685\mathrm{}\mathrm{MeV}/c$. Absolute cross sections were measured at three electron kinematics. For the measured missing momenta range from 10 to $165\mathrm{MeV}/c$, no strength is observed for missing energies higher than 20 MeV. Distorted momentum distributions were extracted for the two-body breakup and the continuum. The longitudinal and transverse nature of the cross sections is well described by a widely used prescription of the off-shell electron-nucleon cross section. The results are compared to modern three-body calculations and to previous data.

In a series of measurements with Gammasphere, striking differences were found between the yrast and negative parity bands in ${}^{238–240}\mathrm{Pu}$ and those in ${}^{241–244}\mathrm{Pu}$. These differences can be linked to variations with mass of the strength of octupole correlations. At the highest spins, ${}^{238–240}\mathrm{Pu}$ are found to exhibit properties associated with stable octupole deformation, suggesting that a transition with spin from a vibration to stable deformation may have occurred.

The induced pairing interaction arising from the exchange of low-lying collective surface vibrations among nucleons moving in time reversal states close to a Fermi energy is found to lead to values of the pairing gap which constitute a large fraction of those experimentally observed.

The mechanism of backbending in ${}^{48}\mathrm{Cr}$ is investigated in terms of the projected shell model and the generator coordinate method. It is shown that both methods are reasonable shell model truncation schemes. These two quite different quantum mechanical approaches lead to a similar conclusion that the backbending is due to a band crossing involving an excited band which is built on simultaneously broken neutron and proton pairs in the “intruder” subshell $f_{7/2}$. It is pointed out that this type of band crossing is usually known to cause the second backbending in rare-earth nuclei.

Low-density nuclear matter at finite temperature is considered representing the strong coupling situation of a highly correlated fermion system. One-particle self-energies and the density of states in the vicinity of the pairing transition point are presented. Within the Green function approach, model calculations are performed using the thermodynamic $T$ matrix in ladder approximation. As a main result the formation of a pseudogap in the level density near the critical temperature of the pairing phase transition has been found. It is shown that compared to mean-field approaches the scenario of the onset of the pairing transition is essentially changed if correlations are taken into account.

Midrapidity antihyperon $\left(\overline{Y}\right)$ production in nuclear collisions is studied using a new hadronic string mechanism. This mechanism of baryon junction-antijunction $\left(J\overline{J}\right)$ loops is an extension of the baryon junction exchange mechanism recently proposed to explain valence baryon number transport. These loops are shown to enhance the $\overline{\Lambda }$, $\overline{\Xi }$, and $\overline{\Omega }$ as well as lead to long range rapidity correlations. Comparisons are made with recent observations of $\mathrm{Pb}+\mathrm{Pb}\to Y\overline{Y}X$ at the CERN Super Proton Synchrotron (SPS), and predictions are made for upcoming experiments.

We report on a measurement of subthreshold $\eta$ and ${\pi }^0$ mesons in the reaction $\mathrm{Ar}+\mathrm{Ca}$ at $180A$ MeV. We find that the ratio of the $\eta$ to ${\pi }^0$ meson-production cross section is more than a factor of 20 smaller than the one expected from threshold-energy scaling of meson production. In addition, the multiplicity of high $m_t$ ${\pi }^0$ increases faster with the centrality of the reaction than the multiplicity of the bulk of ${\pi }^0$ mesons. This behavior is explained by the rescattering of $\pi$ mesons in nuclear matter at the origin of most energetic particles.

We found strong evidence for the existence of supersymmetry by studying the odd-odd nucleus ${}^{196}\mathrm{Au}$ using the ${}^{197}\mathrm{Au}(\overrightarrow{d},t)$, ${}^{197}\mathrm{Au}(p,d)$, and ${}^{198}\mathrm{Hg}(\overrightarrow{d},\alpha )$ transfer reactions. High resolution ${}^{196}\mathrm{Pt}(p,d)$ and ${}^{196}\mathrm{Pt}(\overrightarrow{d},t)$ transfer experiments performed in parallel yielded an improved level scheme of ${}^{195}\mathrm{Pt}$. Using extended supersymmetry, a single fit of the six parameter eigenvalue expression yielded a complete description of all observed low-lying excited states in the four nuclei forming the supermultiplet. The detailed comparison of the transfer amplitudes the odd-odd member of the supermultiplet ${}^{196}\mathrm{Au}$ using a semimicroscopic transfer operator provides, then, evidence that this description is correct.

A Comment on the Letter by M. Drochner et al., Phys. Rev. Lett. 77, 454 (1996). The authors of the Letter offer a Reply.

A Reply to the Comment by J. Blomgren and N. Olsson.