We identify a $J^{\pi }{=3\mathrm{}}_{\mathrm{ms}}^{+}$ state in ${}^{94}\mathrm{Mo}$. This identification is based on six $M1\mathrm{}$ and $E2\mathrm{}$ strengths and is the first identification of a $3_{\mathrm{ms}}^{+}$ state from $B\left(M1\mathrm{}\right)$ and $B\left(E2\mathrm{}\right)$ values. The transition strengths were determined from the measurement of Doppler shifts, branching ratios, and $E2\mathrm{}/M1\mathrm{}$ mixing ratios, obtained from $\gamma \gamma$ directional correlations following the ${}^{91}\mathrm{Zr}(\alpha ,n)$ reaction and the ${\beta }^{+}$ decay of ${}^{94}{\mathrm{Tc}}^m$. The interacting boson model agrees with the observations, which prove the $2^{+}$ mixed-symmetry states to be a building block in nuclear structure.

The ${}^{\mathrm{nat}}\mathrm{Pb}{(}^3\mathrm{He},tp)$ reaction at $E{(}^3\mathrm{He})=177\mathrm{MeV}$ was studied to identify $2ħ\omega$ isovector monopole strength in Bi isotopes. Monopole strength was found in the region $-45<Q<-30\mathrm{MeV}$ in the coincidence data. The cross section is compared with distorted-wave Born approximation calculations for non-spin-flip and spin-flip isovector monopole resonances. The observed spin-flip and non-spin-flip monopole strengths in the proton-decay channel amount to $20\%$ of the respective non-energy-weighted sum rule.

It is shown that several effects are responsible for deviations of the intensity distributions from the Porter-Thomas law. Among these are genuine symmetry breaking, such as isospin, the nature of the transition operator, truncation of the Hilbert space in shell model calculations, and missing transitions.

It is found that the suppression due to two-body $\Lambda N-\Sigma N$ coupling solves the overbinding problem in ${}_{\Lambda }^5\mathrm{He}$ but it, in turn, causes a severe underbinding in the four-body systems. The shortage of this binding is overcome by introducing explicitly the $\Lambda -\Sigma$ coupling which is equivalent to the $\Lambda \mathrm{NN}$ three-body force. This three-body force becomes strong in the $0^{+}$ states of ${}_{\Lambda }^4\mathrm{H}$ and ${}_{\Lambda }^4\mathrm{He}$ according to the coherently added enhancement. The $0^{+}-1^{+}$ splitting in ${}_{\Lambda }^4\mathrm{H}$ and ${}_{\Lambda }^4\mathrm{He}$ is found partly due to the $\Lambda N$ spin-spin interaction and partly due to the $\Lambda -\Sigma$ coupling in the recent Nijmegen soft-core potential.

The entry distribution in angular momentum and excitation energy for the formation of ${}^{254}\mathrm{No}$ has been measured after the ${}^{208}\mathrm{Pb}{(}^{48}\mathrm{Ca},2n)$ reaction at 215 and 219 MeV. This nucleus is populated up to spin $22ħ$ and excitation energy $\gtrsim 6\mathrm{MeV}$ above the yrast line, with the half-maximum points of the energy distributions at $\sim 5\mathrm{MeV}$ for spins between $12ħ$ and $22ħ$. This suggests that the fission barrier is $\gtrsim 5\mathrm{MeV}$ and that the shell-correction energy persists to high spin.

Measurements of the suppression of the yield per nucleon of $J/\psi$ and ${\psi }^{\prime }$ production for 800 GeV/ $c$ protons incident on heavy nuclear targets, relative to light nuclear targets, have been made with very broad coverage in $x_F$ and $p_T$. The observed suppression is smallest at $x_F$ values of 0.25 and below, and increases at larger values of $x_F$. It is also strongest at small $p_T$. Substantial differences between ${\psi }^{\prime }$ and $J/\psi$ production are observed for the first time in $p-A$ collisions. The suppression for ${\psi }^{\prime }$ production is stronger than that for $J/\psi$ for $x_F$ near zero, but becomes comparable to that for $J/\psi$ for $x_F>0.6\mathrm{}$.

The effective restoration of the chiral ${\mathrm{U}}_A\left(1\right)$ symmetry in strong interactions is studied using the linear chiral $\mathrm{SU}\left(3\right)\times \mathrm{SU}\left(3\right)$ model at finite temperatures. We find that the disappearance of the chiral anomaly causes a considerable change in the meson mass spectrum. We propose several signals for detecting this chiral phase in ultrarelativistic heavy-ion collisions: The $\eta /{\pi }^0$ ratio is enhanced by an order of magnitude, the $a_0$ is suppressed in the $K\overline{K}$ mass spectrum, and the scalar $\kappa$ meson appears as a peak just below the $K^{*}\left(892\right)$ in the invariant $\pi K$ mass spectrum.

We have measured the cross section for quasielastic $1p$-shell proton knockout in the ${}^{16}\mathrm{O}\left({e,e}^{\prime }p\right)$ reaction at $\omega =0.439\mathrm{}\mathrm{GeV}$ and $Q^2=0.8\mathrm{}(\mathrm{GeV}/c{)}^2$ for missing momentum $P_{\mathrm{miss}}\le 355\mathrm{MeV}/c$. We have extracted the response functions $R_{L+TT}$, $R_T$, $R_{\mathrm{LT}}$, and the left-right asymmetry, $A_{\mathrm{LT}}$, for the ${1p}_{1/2}$ and the ${1p}_{3/2}$ states. The data are well described by relativistic distorted wave impulse approximation calculations. At large $P_{\mathrm{miss}}$, the structure observed in $A_{\mathrm{LT}}$ indicates the existence of dynamical relativistic effects.

Photon absorption by a quark in one nucleon followed by its high-momentum transfer interaction with a quark in the other may produce two final-state nucleons with high relative momentum. We sum the relevant quark rescattering diagrams to show that the scattering amplitude depends on a convolution between the large angle $\mathrm{pn}$ scattering amplitude, the hard photon-quark interaction vertex, and the low-momentum deuteron wave function. The computed absolute values of the cross section are in reasonable agreement with the data.

We present the first excitation function of ${\pi }^{-}$ intensity interferometry at Alternating Gradient Synchrotron (AGS) energies (2–8 A GeV). The sensitivity of the multidimensional correlation functions to the geometry and dynamics of the pion-emitting system provides a stringent test of transport models of heavy ion collisions. Detailed comparisons with a realistic transport model, both with and without an explicit nuclear mean field, suggest that the beam energy evolution in the reaction dynamics is different in the model than in the data. A significantly increased ${\pi }^{-}$ emission time scale, which has been suggested as a signal of the onset of the transition to quark-gluon plasma, is not observed.

For high-energy nucleus-nucleus collisions, we show that a combination of space-momentum correlations characteristic of radial expansion, together with the correlation between the position of a nucleon in the nucleus and its stopping, results in a very specific rapidity dependence of directed flow: a reversal of sign in the midrapidity region. We support our argument by RQMD model calculations for $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s}=200A\mathrm{GeV}$.

Vector mesons are produced copiously in peripheral relativistic heavy-ion collisions. Virtual photons from one ion can fluctuate into quark-antiquark pairs and scatter from the second ion, emerging as vector mesons. The emitter and target are indistinguishable, so emission from the two ions will interfere. Vector mesons have negative parity so the interference is destructive, reducing the production of mesons with small transverse momentum. The mesons are short lived, and decay before emission from the two ions can overlap. However, the decay-product wave functions overlap and interfere since they are produced in an entangled state, providing an example of the Einstein-Podolsky-Rosen paradox.

Cross sections for elastic Compton scattering from the deuteron were measured over the laboratory angles ${\theta }_{\gamma }=35\mathrm{}°–150°$. Tagged photons in the laboratory energy range $E_{\gamma }=84\mathrm{}–105\mathrm{MeV}$ were scattered from liquid deuterium and detected in the large-volume Boston University NaI spectrometer. Using the calculations of Levchuk and L'vov, along with the measured differential cross sections, the isospin-averaged nucleon polarizabilities in the deuteron were estimated. A best-fit value of $(\overline{\alpha }-\overline{\beta })=2.6\mathrm{}\pm 1.8$ was determined, constrained by dispersion sum rules. This is markedly different from the accepted value for the proton of $(\overline{\alpha }-\overline{\beta }{)}_p=10.0\mathrm{}\pm 1.5\pm 0.9$.

Out of plane measurements of the angular correlations for the ${}^{12}\mathrm{C}\left({e,e}^{\prime }n\right)$ reaction have been performed for the first time in the giant resonance region. The cross sections were directly separated into the longitudinal and transverse, longitudinal-transverse, and transverse-transverse components. The cross section at the peak of the giant resonance ( $\omega =22.5\mathrm{}\mathrm{MeV}$) has been found to be almost all longitudinal. It was reproduced by the multipole expansion with $E0\mathrm{}$ and $E2\mathrm{}$ components besides $E1\mathrm{}$. The longitudinal-transverse component might have a maximum around 24 MeV. The transverse-transverse component is very small over the giant resonance.

The fusion-fission cross sections of the ${}^4\mathrm{He}{+}^{238}\mathrm{U}$ and ${}^6\mathrm{He}{+}^{238}\mathrm{U}$ systems have been measured, at Louvain-la-Neuve, for energies around and below the Coulomb barrier, using an array of Si detectors surrounding a ${\mathrm{UF}}_4$ target. The data taken with ${}^4\mathrm{He}$ are in good agreement with previous data and with the coupled channel fusion calculation performed with ECIS. The ${}^6\mathrm{He}$ data show a regular trend with a large enhancement below the barrier which is attributed to the halo structure of the ${}^6\mathrm{He}$ nucleus.

A Comment on the Letter by C. B. Collins, et al., Phys. Rev. Lett. 82, 695 (1999). The authors of the Letter offer a Reply.

A Comment on the Letter by C. B. Collins, et al., Phys. Rev. Lett. 82, 695 (1999). The authors of the Letter offer a Reply.

A Comment on the Letter by C. B. Collins, et al., Phys. Rev. Lett. 82, 695 (1999). The authors of the Letter offer a Reply.

A Reply to the Comment by Silviu Olariu and Agata Olariu. Also D. P. McNabb, et al. also P. von Neumann-Cosel and A. Richter.

X-ray bursts have been suggested as a possible site for the astrophysical $\mathrm{rp}$-process. The time scale for the process is governed by $\beta$-decay half-lives of several even-even $N=Z$ waiting point nuclei, in particular, $N=Z=40\mathrm{}$ ${}^{80}\mathrm{Zr}$. A $4.1\left(\{+0.8\mathrm{}\}\{-0.6\mathrm{}\}\right)-\mathrm{s}$ ${\beta }^{+}/\mathrm{EC}$ half-life for ${}^{80}\mathrm{Zr}$ was determined by observing delayed 84-keV $\gamma$ rays depopulating a $T_{1/2}=4\mathrm{}-\mu \mathrm{s}$ isomer at 312 keV in the daughter ${}^{80}\mathrm{Y}$. As this half-life is lower than many previously predicted values, the calculated excessive production of $A=80\mathrm{}$ nuclides in astrophysical x-ray burst scenarios is reduced, and less extreme conditions are necessary for the production of heavier nuclides.