The two-body random ensemble for a many-body bosonic theory is mapped to a problem of random polynomials on the unit interval. In this way one can understand the predominance of $0^{+}$ ground states, and analytic expressions can be derived for distributions of lowest eigenvalues, energy gaps, density of states, and so forth. Recently studied nuclear spectroscopic properties are addressed.

A new class of dynamic symmetries is introduced. It is suggested that an element of this class, associated with zeros of Bessel functions, be used to describe spectra of nuclei at or around the critical point of the $\mathrm{U}\left(5\right)-\mathrm{SO}\left(6\right)$ shape phase transition, and, in general, spectra of systems undergoing a (second order) phase transition between the algebraic structures $\mathrm{U}(n-1\mathrm{})$ and $\mathrm{SO}\left(n\right)$.

Evidence for the first empirical example of a transitional dynamical symmetry at a critical point is discussed in the spectrum of ${}^{134}\mathrm{Ba}$. The role of such classes of symmetries in nuclear structural evolution is also discussed.

In this paper we study a microcanonical lattice gas model with a constrained average volume. We show that the caloric curve explicitly depends on the considered transformation of the volume with the excitation energy and so does not bear direct information on the characteristics of the phase transition. Conversely, partial energy fluctuations are demonstrated to be a direct measure of the equation of state. Since the heat capacity has a negative branch in the phase transition region, the presence of abnormally large kinetic energy fluctuations is a signal of the liquid-gas phase transition.

Modified quark fragmentation functions in deeply inelastic $\mathrm{eA}$ collisions and their QCD evolution equations are derived for the first time in the framework of multiple parton scattering. Induced radiation gives rise to additional terms in the evolution equations and thus softens the modified quark fragmentation functions. The results in the next-leading-twist depend on both diagonal and off-diagonal twist-four parton distributions and the combination of which clearly manifests the LPM interference pattern. The predicted modification depends quadratically on the nuclear size ( $A^{2/3}$). Generalization to the case of hot QCD medium is also discussed.

A measurement of direct photon production in ${}^{208}\mathrm{Pb}{+}^{208}\mathrm{Pb}$ collisions at $158A$ GeV has been carried out in the CERN WA98 experiment. The invariant yield of direct photons in central collisions is extracted as a function of transverse momentum in the interval $0.5<\mathrm{}{p}_T<4\mathrm{}\mathrm{GeV}/c$. A significant direct photon signal, compared to statistical and systematical errors, is seen at $p_T>1.5\mathrm{}\mathrm{GeV}/c$. The result constitutes the first observation of direct photons in ultrarelativistic heavy-ion collisions. It could be significant for diagnosis of quark-gluon-plasma formation.

We present the first measurement of pseudorapidity densities of primary charged particles near midrapidity in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=56\mathrm{}$ and $130\mathrm{GeV}$. For the most central collisions, we find the charged-particle pseudorapidity density to be $\mathrm{dN}/d\eta {|}_{|\eta |<1\mathrm{}}=408\mathrm{}\pm 12\left(\mathrm{stat}\right)\pm 30\left(\mathrm{syst}\right)$ at $56\mathrm{GeV}$ and $555\pm 12\left(\mathrm{stat}\right)\pm 35\left(\mathrm{syst}\right)$ at $130\mathrm{GeV}$, values that are higher than any previously observed in nuclear collisions. Compared to proton-antiproton collisions, our data show an increase in the pseudorapidity density per participant by more than $40\%$ at the higher energy.

Three-particle correlations have been measured for identified ${\pi }^{-}$ from central $158A\mathrm{GeV}$ $\mathrm{Pb}+\mathrm{Pb}$ collisions by the WA98 experiment at CERN. A substantial contribution of the genuine three-body correlation has been found as expected for a mainly chaotic and symmetric source.

We have measured the transverse asymmetry $A_{T^{\prime }}$ in ${}^3\overrightarrow{\mathrm{He}}\left(\overrightarrow{e}{,e}^{\prime }\right)$ quasielastic scattering in Hall A at Jefferson Laboratory with high precision for $Q^2$ values from 0.1 to $0.6(\mathrm{GeV}/c{)}^2$. The neutron magnetic form factor $G_M^n$ was extracted based on Faddeev calculations for $Q^2=0.1\mathrm{}$ and $0.2(\mathrm{GeV}/c{)}^2$ with an experimental uncertainty of less than $2\%$.

Production of $p$-wave pions in nucleon-nucleon collisions is studied according to an improved power counting that embodies the constraints of chiral symmetry. Contributions from the first two nonvanishing orders are calculated. We find reasonable convergence and agreement with data for a spin-triplet cross section in $\mathrm{pp}\to \mathrm{pp}{\pi }^0$, with no free parameters. Agreement with existing data for a spin-singlet cross section in $\mathrm{pp}\to \mathrm{pn}{\pi }^{+}$ constrains a short-range operator shown recently to contribute significantly to the three-nucleon potential.

The $\beta$-delayed $\alpha$ spectrum from the decay of ${}^8\mathrm{B}$ has been measured with a setup that minimized systematic uncertainties that affected previous measurements. Consequently the deduced neutrino spectrum presents much smaller uncertainties than the previous recommendation [J. N. Bahcall et al., Phys. Rev. C 54, 411 (1996)]. The ${}^8\mathrm{B}$ $\nu$ spectrum is found to be harder than previously recommended with about $(10–20)\%$ more neutrinos at energies between 12–14 MeV. The integrated cross sections of the ${}^{37}\mathrm{Cl}$, ${}^{71}\mathrm{Ga}$, ${}^{40}\mathrm{Ar}$, and Super-Kamiokande detectors are, respectively, $3.6\%$, $1.4\%$, $5.7\%$, and $2.1\%$ larger than previously thought.

The ${}^{48}\mathrm{Ca}\left({e,e}^{\prime }n\right)$ reaction has been investigated for excitation energies 11–25 MeV and momentum transfers $0.22–0.43{\mathrm{fm}}^{-1\mathrm{}}$ at the superconducting Darmstadt electron linear accelerator S-DALINAC. Electric dipole and quadrupole plus monopole strength distributions are extracted from a multipole decomposition of the spectra. Their fragmented structure is described by microscopic calculations allowing for coupling of the basic particle-hole excitations to more complex configurations. Comparison of the excitation spectrum of the residual nucleus ${}^{47}\mathrm{Ca}$ with statistical model calculations reveals a $39\left(5\right)\%$ contribution of direct decay to the damping of the giant dipole resonance.

Spectroscopic studies of two $\beta$ rays from ${}^{100}\mathrm{Mo}$ are shown to be of potential interest for investigating both the Majorana $\nu$ mass by neutrinoless double $\beta$ decay $\left(0\nu \beta \beta \right)$ and low energy solar $\nu$'s by inverse $\beta$ decay. With a multiton ${}^{100}\mathrm{Mo}$ detector, coincidence studies of correlated $\beta \beta$ from $0\nu \beta \beta$, together with the large $Q$ value ( $Q_{\beta \beta }$), permit identification of the $\nu$-mass term with a sensitivity of $\sim 0.03\mathrm{eV}$. Correlation studies of the inverse $\beta$ decay and the successive $\beta$ decay of ${}^{100}\mathrm{Tc}$, together with the large capture rates for low energy solar $\nu$'s, make it possible to detect, in real time, individual low energy solar $\nu$ in the same detector.

A Comment on the Letter by J. Kasagi et al., Phys. Rev. Lett. 79, 371 (1997). The authors of the Letter offer a Reply.

A Reply to the Comment by N. V. Eremin, G. Fazio, and G. Giardina.

The invariant cross section as a function of transverse momentum for antideuterons produced in $158A\mathrm{GeV}/c$ per nucleon $\mathrm{Pb}+\mathrm{Pb}$ central collisions has been measured by the NA44 experiment at CERN. This measurement, together with a measurement of antiprotons, allows for the determination of the antideuteron coalescence parameter. The extracted coalescence radius is found to agree with the deuteron coalescence radius and radii determined from two particle correlations.

We present Experiment 864's measurement of invariant antideuteron yields in $11.5A$ $\mathrm{GeV}/c$ $\mathrm{Au}+\mathrm{Pt}$ collisions. The analysis includes $250\times {10}^6$ triggers representing $14\times {10}^9$ $10\%$ central interactions sampled for events with high mass candidates. We find $\left(1/2\pi p_t\right)d^{2}N/{\mathrm{dydp}}_t=3.5\mathrm{}\pm 1.5\left(\mathrm{stat}{)}_{-0.5\mathrm{}}^{+0.9\mathrm{}}\right(\mathrm{syst})\times {10}^{-8\mathrm{}}{\mathrm{GeV}}^{-2\mathrm{}}{c}^2$ for $1.8<y<\mathrm{}2.2\mathrm{}$, $〈p_t〉=0.35\mathrm{}\mathrm{GeV}/c$ ( $y_{\mathrm{c}.\mathrm{m}.\mathrm{}}=1.6\mathrm{}$) and $3.7\pm 2.7\left(\mathrm{stat}{)}_{-1.5\mathrm{}}^{+1.4\mathrm{}}\right(\mathrm{syst})\times {10}^{-8\mathrm{}}$ ${\mathrm{GeV}}^{-2\mathrm{}}{c}^2$ for $1.4<y<\mathrm{}1.8\mathrm{}$, $〈p_t〉=0.26\mathrm{}\mathrm{GeV}/c$, and a coalescence parameter $\overline{B_2}$ of $4.1\pm 2.9\left(\mathrm{stat}{)}_{-2.4\mathrm{}}^{+2.3\mathrm{}}\right(\mathrm{syst})\times {10}^{-3\mathrm{}}{\mathrm{GeV}}^2{c}^{-3\mathrm{}}$. Implications for coalescence and antimatter annihilation are discussed.

A novel state of matter has been hypothesized to exist during the early stage of relativistic heavy-ion collisions, with normal hadrons not appearing until several $\mathrm{fm}/c$ after the start of the reaction. To test this hypothesis, correlations between charges and their associated anticharges are evaluated with the use of balance functions. It is shown that late-stage hadronization is characterized by tightly correlated charge-anticharge pairs when measured as a function of relative rapidity.

A superdeformed rotational band has been identified in ${}^{36}\mathrm{Ar}$, linked to known low-spin states, and observed to its high-spin termination at $I^{\pi }{=16\mathrm{}}^{+}$. Cranked Nilsson-Strutinsky and spherical shell model calculations assign the band to a configuration in which four $\mathrm{pf}$-shell orbitals are occupied, leading to a low-spin deformation ${\beta }_2\approx 0.45$. Two major shells are active for both protons and neutrons, yet the valence space remains small enough to be confronted with the shell model. This band thus provides an ideal case to study the microscopic structure of collective rotational motion.

New neutron rich isotopes ${}_{107}^{267}\mathrm{Bh}$ and ${}_{107}^{266}\mathrm{Bh}$ were produced in bombardments of a ${}^{249}\mathrm{Bk}$ target with 117-MeV and 123-MeV ${}^{22}\mathrm{Ne}$ ions at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron. Identification was made by observation of correlated $\alpha$-particle decays between the Bh isotopes and their Db and Lr daughters using a rotating wheel system. ${}^{267}\mathrm{Bh}$ was produced with a cross section of $\approx 70$ pb and decays with a ${17}_{-6\mathrm{}}^{+14\mathrm{}}$ s half life by emission of $\alpha$ particles with an average energy of $8.83\pm 0.03$ MeV. One atom of ${}^{266}\mathrm{Bh}$ was observed, decaying within 1 s by emission of a 9.29-MeV $\alpha$ particle.