Kaon production has been studied in $\mathrm{Ni}+\mathrm{Ni}$ collisions at beam energies of 0.8–1.8 GeV/nucleon with the kaon spectrometer at GSI. The $K^{+}$ production cross section increases as $E_{\mathrm{beam}}^{5.3\pm 0.2}$. Both $K^{+}$ and $K^{-}$ mesons are predominantly produced in central collisions. The $K^{-}/K^{+}$ ratio measured at equivalent beam energies below the respective particle production threshold is considerably larger for $\mathrm{Ni}+\mathrm{Ni}$ collisions than for nucleon-nucleon collisions near threshold. This is evidence for an enhanced $K^{-}$ production in the nuclear medium.

The differential cross section and the transverse-transverse interference structure function for the reaction ${}^2\mathrm{H}\left({e,e}^{\prime }p\right)n$ have been determined at an np invariant mass of 2.16 GeV. The data, covering a 40° range in the proton emission angle, indicate that Δ excitation and subsequent NΔ interaction is the dominant reaction mechanism. Calculations performed within an NΔ coupled-channel approach reproduce the cross section data, but underestimate the $f_{\mathrm{TT}}$ results by 30 to 40 percent.

A four-nucleon calculation of the total ${}^4\mathrm{He}$ photodisintegration cross section is performed. The full final-state interaction is taken into account for the first time. This is achieved via the method of the Lorentz integral transform. Semirealistic $\mathrm{NN}$ interactions are employed. Different from the known partial two-body ${}^4\mathrm{He}(\gamma ,n{)}^3\mathrm{He}$ and ${}^4\mathrm{He}(\gamma ,p{)}^3\mathrm{H}$ cross sections our total cross section exhibits a pronounced giant resonance. Thus, in contrast to older $(\gamma ,np)$ data, we predict quite a strong contribution of the $(\gamma ,np)$ channel at the giant resonance peak energy.

Slow ramping of the CELSIUS storage ring has been utilized to measure the yield of charged pions in proton and heavy ion induced collisions with continuously varying beam energy. Boltzmann-Uehling-Uhlenbeck predictions, including Fermi momenta of nucleons in nuclei, follow the general shape of the $p$-nucleus excitation functions quite well except for a general overestimation of the backward emission. For heavy ion reactions the calculated yield also falls off faster with decreasing beam energy than the data. No statistically significant narrow resonances are observed.

It is proposed that the differences in superdeformed band population observed in recent experiments result from a modification of the compound-nucleus angular momentum distribution due to the presence of low-lying vibrational states in the projectile and/or target nuclei. To test this hypothesis the nucleus ${}^{135}\mathrm{Nd}$ was studied with the reactions ${}^{74}\mathrm{Ge}{+}^{64}\mathrm{Ni}$ and ${}^{26}\mathrm{Mg}{+}^{112}\mathrm{Cd}$. The ${}^{74}\mathrm{Ge}$-induced reaction was found to preferentially populate high-spin states, including superdeformed states. Statistical-model calculations are consistent with the present observations provided coupled-channel effects are taken into account.

The apparent temperatures measured with double ratios of fragment isotope yields display fluctuations that can be attributed to the sequential decay of heavier particle unstable nuclei. Empirical correction factors which minimize these fluctuations have been obtained for 18 isotope thermometers. These factors appear to be common to the three reactions studied suggesting their application to different reactions at different incident energies.

A Comment on the Letter by J. D. Bierman, et al., Phys. Rev. Lett. 76, 1587 (1996). The authors of the Letter offer a Reply.

A Reply to the Comment by C. H. Dasso and J. Fernández-Niello.

A high-sensitivity search for the strangeness $S=-2\mathrm{}$ $H$ dibaryon $\left(\mathrm{uuddss}\right)$ was conducted at the Brookhaven Alternating Gradient Synchrotron (AGS) using the reaction ${}_{}{}^3{}_{}{}^{}H\mathrm{e}\left(K^{-}{,K}^{+}\right)\mathrm{Hn}$ at $P_{K^{-}}=1.8\mathrm{}\mathrm{GeV}/c$. The sensitivity was independent of $H$ lifetime and decay modes. No evidence for $H$ production was observed. In a mass range extending from about $50$ to $380\mathrm{MeV}{/c}^2$ below the $\Lambda \Lambda$ threshold of $2.231\mathrm{GeV}/c^2$, the resulting upper limits on the $H$-production cross section are in the range of $0.058$ to $0.021\mu \mathrm{b}/\mathrm{sr}$, approximately 1 order of magnitude below a theoretical calculation.

Excited states have been observed for the first time in the neutron-deficient ${}^{176,178}\mathrm{Hg}$ nuclei using the recoil-decay tagging (RDT) technique in which prompt $\gamma$ rays are associated with a particular isotope through a correlation with the characteristic ground state $\alpha$ decay. Below $N=102\mathrm{}$, the excitation energy of a rotational band built on a prolate shape $\left({\beta }_2\sim 0.25\right)$ increases with decreasing mass to the point where there is no longer any evidence for its presence at low spin in ${}^{176}\mathrm{Hg}$. The data are in qualitative agreement with recent mean field calculations.

$\Delta I=4\mathrm{}$ bifurcation has been observed in two superdeformed bands, the newly discovered yrast superdeformed band of ${}^{148}\mathrm{Eu}$, and a previously known excited band in ${}^{148}\mathrm{Gd}$. Both of these bands have moments of inertia that are identical to the yrast band of ${}^{149}\mathrm{Gd}$, the first superdeformed band in which this bifurcation was observed. This first observation of $\Delta I=4\mathrm{}$ bifurcation in identical superdeformed bands provides a crucial test of recent models.

A connection is established between an interacting boson model (IBM) that includes $T=1\mathrm{}$ bosons (IBM-3) and one that includes $T=0\mathrm{}$ as well as $T=1\mathrm{}$ bosons (IBM-4). The connection relies on an IBM-4 classification that breaks Wigner's SU(4) symmetry. The resulting generalized IBM-4 is relevant for studying the competition between $T=0\mathrm{}$ and $T=1\mathrm{}$ pairing in $N\sim Z$ nuclei. Consequences for the pair structure in self-conjugate nuclei are discussed.

Nonlocal interactions are an intrinsically quantum phenomenon. In this work we point out that, in the context of heavy ions, such interactions can be studied through the refractive elastic scattering of these systems at intermediate energies. We show that most of the observed energy dependence of the local equivalent bare potential arises from the exchange nonlocality. The nonlocality parameter extracted from the data was found to be very close to the one obtained from folding models. The effective mass of the colliding, heavy-ion, system was found to be close to the nucleon effective mass in nuclear matter.

A Comment on the Letter by D. Beavis, et al., Phys. Rev. Lett. 75, 3633 (1995). The authors of the Letter offer a Reply.

A Reply to the Comment by Y. Pang, D. E. Kahana, and S. H. Kahana.

We have measured the shift and width of the kaonic hydrogen $1s$ state due to the $\overline{K}N$ strong interaction. We have observed, for the first time, distinct $K$-series kaonic hydrogen x rays with good signal-to-noise ratio in the energy spectrum. The measured energy shift and width were determined to be $\Delta E\left(1s\right)=-323\mathrm{}\pm 63\left(\mathrm{stat}\right)\pm 11\left(\mathrm{syst}\right)\mathrm{eV}$ (repulsive) and $\gamma \left(1s\right)=407\mathrm{}\pm 208\left(\mathrm{stat}\right)\pm 100\left(\mathrm{syst}\right)\mathrm{eV}$, respectively.

Inelasticity distributions in high-energy p-nucleus collisions are computed in the framework of the interacting gluon model, with the impact-parameter fluctuation included. A proper account of the peripheral events by this fluctuation has shown to be vital for the overall agreement with several reported data. The energy dependence is found to be weak.

Light charged particle decay from the ${}^{156}\mathrm{Er}$ compound nucleus, populated by ${}^{12}\mathrm{C}{+}^{144}\mathrm{Sm}$ and ${}^{60}\mathrm{Ni}{+}^{96}\mathrm{Zr}$ at the same excitation energy, were measured in coincidence with the evaporation residues. The high energy slope of charged particle spectra for the ${}^{60}\mathrm{Ni}$-induced reaction is steeper than for the ${}^{12}\mathrm{C}$-induced reaction. Model calculations including particle evaporation during fusion result in good agreement with the data. This suggests that the difference in the charged particle spectra between the two entrance channels is due to a longer formation time in the ${}^{60}\mathrm{Ni}$-induced reaction.

Two-particle correlation functions for positive and negative pions have been measured in $\mathrm{Au}+\mathrm{Au}$ collisions at 10.8 GeV/c per nucleon. The data were analyzed using one- and three-dimensional correlation functions. From the results of the three-dimensional fit the phase space density of pions was calculated. It is consistent with local thermal equilibrium.

Multinucleon transfer reactions have been used, for the first time, to populate high-spin bands of alternating parity states in ${}^{218,220,222}\mathrm{Rn}$ and ${}^{222,224,226}\mathrm{Ra}$. The behavior of the angular momentum alignment with rotational frequency for the Rn isotopes is very different when compared with Ra and Th isotopes with $N\approx 134$, indicating a transition from octupole vibrational to stable octupole deformation. Throughout the measured spin range the values of $|D_0/Q_0|$ remain constant for ${}^{222}\mathrm{Ra}$ and ${}^{226}\mathrm{Ra}$ and have a very small value for ${}^{224}\mathrm{Ra}$, suggesting that the charge and mass distributions are not affected appreciably by rotations.