We investigate the degree to which the scaling functions $f\left({\psi }^{\prime }\right)$ derived from inclusive electron-nucleus quasielastic scattering define the same function for different nuclei. In the region where the scaling variable ${\psi }^{\prime }<0\mathrm{}$, we find that this superscaling is experimentally realized to a high degree.

The cross sections of the isovector spin-dipole resonances (SDR) in the Sb isotopes excited by the ${(}^3\mathrm{He},t)$ charge-exchange reaction at 450 MeV for $0°\le {\theta }_t\le 1.15°$ have been measured. The results are compared with the predicted sum-rule strengths related to the difference of neutron and proton root-mean-square radii. Within the model used, the radii differences (neutron-skin thicknesses) deduced for ${}^{114}\mathrm{Sn}$, ${}^{116}\mathrm{Sn}$, ${}^{118}\mathrm{Sn}$, ${}^{122}\mathrm{Sn}$, and ${}^{124}\mathrm{Sn}$ are $\le 0.09$, $0.12\pm 0.06$, $0.13\pm 0.06$, $0.22\pm 0.07$, and $0.19\pm 0.07\mathrm{fm}$, respectively. This result suggests a new method for the measurement of the neutron-skin thicknesses of unstable nuclei.

Lifetimes of states in a rotational-like $M1\mathrm{}$ band in ${}^{110}\mathrm{Cd}$ have been determined through a Doppler-shift attenuation method measurement performed with the Gammasphere array. The deduced $B\left(M1\mathrm{}\right)$ values, which agree well with the predictions of the tilted axis cranking model, clearly confirm that it has the character of a shears band. Using a semiclassical scheme of the coupling of two long $j$ vectors we deduce information on the strength and form of the effective interaction between the constituent nucleons. These results are the first definitive evidence of the shears mechanism and “magnetic rotation” in this mass region.

Exclusive incoherent electroproduction of the ${\rho }^0\left(770\right)$ meson from ${}^1\mathrm{H}$, ${}^2\mathrm{H}$, ${}^3\mathrm{He}$, and ${}^{14}\mathrm{N}$ targets has been studied by the HERMES experiment at squared four-momentum transfer $Q^2>0.4\mathrm{}{\mathrm{GeV}}^2$ and positron energy loss $\nu$ from 9 to 20 GeV. The ratio of the ${}^{14}\mathrm{N}$ to ${}^1\mathrm{H}$ cross sections per nucleon, known as the nuclear transparency, was found to decrease with increasing coherence length of quark-antiquark fluctuations of the virtual photon. The data provide clear evidence of the interaction of the quark-antiquark fluctuations with the nuclear medium.

Spectral enhancement near the ${2m}_{\pi }$ threshold in the $I=J=0\mathrm{}$ channel in nuclei is shown to be a distinct signal of the partial restoration of chiral symmetry. The relevance of this phenomenon with the possible detection of $2{\pi }^0$ and $2\gamma$ in hadron-nucleus and photon-nucleus reactions is discussed.

Exclusive differential cross sections of virtual bremsstrahlung in proton-proton scattering below the pion-production threshold have been measured for the first time. The total cross section integrated over photon invariant masses of 15 to $80\mathrm{MeV}/c^2$ and integrated over the acceptance of the detector is $3.2\pm 0.1\pm 0.5\mathrm{pb}$. The data are compared to a low-energy calculation and a fully relativistic microscopic model, which predict a virtual bremsstrahlung cross section of 3.4 and 5.9 pb, respectively. Over the entire experimentally covered phase space, the low-energy calculation gives a better description of the data than the microscopic model.

Net proton and negative hadron spectra for central $\mathrm{Pb}+\mathrm{Pb}$ collisions at 158 GeV per nucleon at the CERN Super Proton Synchrotron were measured and compared to spectra from lighter systems. Net baryon distributions were derived from those of net protons. Stopping (rapidity shift with respect to the beam) and mean transverse momentum $〈p_T〉$ of net baryons increase with system size. The rapidity density of negative hadrons scales with the number of participant nucleons for nuclear collisions, whereas their $〈p_T〉$ is independent of system size. The $〈p_T〉$ dependence upon particle mass and system size is consistent with larger transverse flow velocity at midrapidity for $\mathrm{Pb}+\mathrm{Pb}$ compared to $\mathrm{S}+\mathrm{S}$ central collisions.

The first fully on-line isotope shift measurement of a radioactive refractory element is reported. Collinear laser-induced fluorescence measurements were made on the radioactive isotopes ${}^{170,172,173,174}\mathrm{Hf}$ produced with a flux of $2–3\times {10}^3$ ions per second from an ion-guide fed isotope separator. The method may be applied to all elements and isomers with lifetimes as short as 1 ms. The systematics of the new charge radii measurements are well reproduced by theory, with the maximum deformation in the chain occurring significantly below the midshell.

Analyzing powers for $\overrightarrow{p}n\to \mathrm{pp}\left({}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}\right){\pi }^{-}$ were measured at beam energies 353, 404, and 440 MeV by extracting the quasifree process from $\overrightarrow{p}d\to \mathrm{ppp}{\pi }^{-}$. Partial wave amplitude analysis yields a significant contribution from the isospin 1, $s$-wave channel. This contribution is relatively much larger than that expected from theoretical models which have been successful in describing the isospin 1, $s$-wave channel behavior of $\mathrm{pp}\to \mathrm{pp}{\pi }^0$ cross sections at threshold.

Elliptic flow of the hot, dense system which has been created in nucleus-nucleus collisions develops as a response to the initial azimuthal asymmetry of the reaction region. Here it is suggested that the magnitude of this response shows a highly sensitive dependence on the centrality of collisions for which the system passes through a first-order or rapid transition between quark-gluon plasma and hadronic matter. We have studied the system $\mathrm{Pb}\left(158A\mathrm{GeV}\right)$ on Pb employing a recent version of the transport theoretical approach relativistic quantum molecular dynamics and find the conjecture confirmed. The novel phase transition signature may be observable in present and forthcoming experiments at CERN-SPS and at RHIC, the BNL collider.

The nuclear overlap zone in noncentral relativistic heavy ion collisions is azimuthally very asymmetric. By varying the angle between the axes of deformation and the transverse direction of the pair momenta, the transverse Hanbury-Brown–Twiss radii oscillate in a characteristic way. It is shown that these oscillations allow determination of source sizes, deformations, as well as the opacity and duration of emission of the source created in any noncentral high energy nuclear collisions. The behavior of the physical quantities with centrality of the collisions is discussed—in particular, changes caused by a possible phase transition to a quark-gluon plasma.

Inclusive electron scattering is measured with 4.045 GeV incident beam energy from C, Fe, and Au targets. The measured energy transfers and angles correspond to a kinematic range for Bjorken $x>\mathrm{}1\mathrm{}$ and momentum transfers from $Q^2=1\mathrm{}–7(\mathrm{GeV}/c{)}^2$. When analyzed in terms of the $y$-scaling function the data show for the first time an approach to scaling for values of the initial nucleon momenta significantly greater than the nuclear matter Fermi momentum (i.e., $>0.3\mathrm{}\mathrm{GeV}/c$).

As an alternative to Wigner's spin-isospin SU(4) symmetry, known to be broken in heavier nuclei, a pseudo-SU(4) symmetry is proposed which follows from the combined invariance in pseudospin and isospin. The pseudo-SU(4) scheme is tested in $N,Z>\mathrm{}28\mathrm{}$ nuclei, and its consequences with regard to Gamow-Teller $\beta$ decay are pointed out.

We suggest that low-lying eigenvalues of realistic many-body Hamiltonians, given, as in the nuclear shell model, by large matrices, can be calculated by the diagonalization of truncated matrices with the exponential extrapolation of the results. We show numerical data confirming this conjecture. We argue that the exponential convergence may be a generic feature of complex systems where the wave functions are localized in an appropriate basis.

Two $\alpha$-decaying isomeric states were observed in ${}^{191}\mathrm{Po}$ with $E_{\alpha }=7334\mathrm{}\left(10\right)\mathrm{keV}$ and $\mathrm{T}{}_{1/2}=22\mathrm{}\left(1\right)\mathrm{ms}$ for ${}^{191g}\mathrm{Po}$ and $\mathrm{E}{}_{\alpha }=7378\mathrm{}\left(10\right)\mathrm{keV}$ and $\mathrm{T}{}_{1/2}=98\mathrm{}\left(8\right)\mathrm{ms}$ for ${}^{191m}\mathrm{Po}$. Evidence was found for fine-structure decay to excited levels in the ${}^{187}\mathrm{Pb}$ daughter nucleus. The tentative interpretation of these new levels involves the weak coupling of the odd neutron to an intruder $\pi \left(2p-2h\right)$ deformed $0^{+}$ state in the even-even core. The long half-life of the ${}^{191m}\mathrm{Po}$ $(\Delta l=0\mathrm{})$ $\alpha$ decay points to a deformed ${13/2}^{+}$ isomeric state in ${}^{191}\mathrm{Po}$.

The total ${\beta }^{-}$ decay energies of 14 nuclides in the vicinity of ${}^{132}\mathrm{Sn}$ have been measured using high resolution spectroscopic methods. The present results derived for the atomic masses in this region are significantly more precise than the previously accepted values, and differ significantly from these in some cases. The precision of the new mass values surpasses that expected from the systems currently proposed for direct mass measurements of nuclei far from stability. The present results resolve a recently observed and highly puzzling discrepancy between the experimental mass values in the ${}^{132}\mathrm{Sn}$ region and theoretical systematics.

We show that the assumption of dropping meson masses together with conventional many-body effects, implemented in the relativistic Dirac-Brueckner formalism, explains nuclear saturation. We use a microscopic model for correlated $2\pi$ exchange and include the standard many-body effects on the in-medium pion propagation, which initially increase the attractive nucleon-nucleon ( $\mathrm{NN}$) potential with density. For the vector meson exchanges in both the $\pi \pi$ and $\mathrm{NN}$ sector, we assume Brown-Rho scaling which—in concert with “chiral” $\pi \pi$ contact interactions—reduces the attraction at higher densities.

A Comment on the Letter by Hiroshi Toki and Lian-Ao Wu, Phys. Rev. Lett. 79, 2006 (1997).

Precisely measured Drell-Yan cross sections for 800 GeV protons incident on a variety of nuclear targets exhibit a deviation from linear scaling in the atomic number $A$. We show that this deviation can be accounted for by energy degradation of the proton as it passes through the nucleus if account is taken of the time delay of particle production due to quantum coherence. We infer an average proper coherence time of $0.4\pm 0.1\mathrm{fm}/c$, corresponding to a coherence path length of $8\pm 2$ fm in the rest frame of the nucleus.