The Euclidean black hole has topology ${\mathit{gerR}}^2$×${\mathit{scrS}}^{\mathit{d}\mathrm{-}2}$. It is shown that, in Einstein’s theory the deficit angle of a cusp at any point in ${\mathit{gerR}}^2$ and the area of the ${\mathit{scrS}}^{\mathit{d}\mathrm{-}2}$ are canonical conjugates. The black hole entropy emerges as the Euler class of a small disk centered at the horizon multiplied by the area of the ${\mathit{scrS}}^{\mathit{d}\mathrm{-}2}$ there. These results are obtained through dimensional continuation of the Gauss-Bonnet theorem. The extension to the most general action yielding second order field equations for the metric in any spacetime dimension is given.

An observation of an excited ${\mathrm{\Lambda }}_{\mathit{c}}^{+\mathrm{*}}$ baryon decaying to ${\mathrm{\Lambda }}_{\mathit{c}}^{+}$${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$, with ${\mathrm{\Lambda }}_{\mathit{c}}^{+}$→${\mathit{pK}}^{\mathrm{-}}$${\mathrm{\pi }}^{+}$, is presented. We reconstruct 39.7±8.7${\mathrm{\Lambda }}_{\mathit{c}}^{+\mathrm{*}}$ baryons with a mass of 340.4±0.6±0.3 MeV/${\mathit{c}}^2$ above the ${\mathrm{\Lambda }}_{\mathit{c}}^{+}$ mass. The upper limit on the resonant branching ratio is B(${\mathrm{\Lambda }}_{\mathit{c}}^{+\mathrm{*}}$→${\mathrm{\Sigma }}_{\mathit{c}}$${\mathrm{\pi }}^{\pm }$)/B(${\mathrm{\Lambda }}_{\mathit{c}}^{+\mathrm{*}}$→${\mathrm{\Lambda }}_{\mathit{c}}^{+}$ ${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$)<36% at the 90% confidence level.

We report on a search for first generation leptoquarks with the DO/ detector at the Fermilab Tevatron pp¯ collider at √s =1.8 TeV. This search is based on 15 ${\mathrm{pb}}^{\mathrm{-}1}$ of data. Leptoquarks are assumed to be produced in pairs and to decay into an electron + quark with branching ratio β. No leptoquark candidates were found. We obtain cross section times branching ratio limits as a function of leptoquark mass. For pair production of scalar leptoquarks, we set a leptoquark mass limit of 133 GeV for β=1 and 120 GeV for β=0.5 at 95% confidence level.

A unified picture of nucleon-antinucleon annihilation into pions emerges from a classical description of the pion wave produced in annihilation and the subsequent quantization of that wave as a coherent state. When the constraints of energy-momentum and isospin conservation are imposed on the coherent state, the pion number distribution and charge ratios are found to be in agreement with experiment.

The polarized target asymmetry ${\mathit{A}}_{\mathit{N}}$ for ${\mathrm{\pi }}^{\mathrm{-}}$p→→γn has been measured by coincident detection of the γ and the neutron at several angles across the Δ resonace energy region. A high-resolution NaI γ spectrometer together with good time-of-flight information for the neutron resulted in excellent separation of this radiative capture reaction from the much higher cross-section charge exchange reaction ${\mathrm{\pi }}^{\mathrm{-}}$p→→${\mathrm{\pi }}^0$n. Statistical uncertainties are Δ${\mathit{A}}_{\mathit{N}}$=0.02-0.04, representing a significant improvement over previous results. The new data are discussed in the context of recent theoretical models.

Transverse momentum spectra of η mesons have been measured near the free nucleon-nucleon production threshold in the heavy ion reactions ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$+ ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$ + ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Zr}$, and ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$+ ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ at 1.0A GeV and also in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$+ ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Ca}$ at 1.5A GeV. The measured transverse momentum distributions are compared to model calculations. The relative abundance of Δ(1232) and N(1535) resonances excited in the collision is deduced. A comparison to pion data reveals scaling with the transverse mass of the emitted meson.

The shell structure of exotic nuclei near proton and neutron drip lines is discussed in terms of the self-consistent mean-field theory. It is demonstrated that when approaching the neutron drip line, the neutron density becomes very diffused and the single-particle spectrum shows similarities to that of the harmonic oscillator with spin-orbit term. Interaction between bound orbitals and continuum is shown to result in quenching of shell effects in light and medium systems.

Complementing the work of Alhassid et al. we study the global dynamics of the averaged system of the generalized van der Waals interaction in the reduced space which is a two-dimensional sphere. We find lines of local ‘‘pitchfork’’ and global ‘‘oyster’’ bifurcations emerging from the known integrable cases β=1/2, 1, 2; this explains the chaos-order-chaos transition. We present the libration and circulation modes of the Runge-Lenz vector and its stability domains. The appearance-disappearance pattern of separatrices for the known integrable cases leads us to conjecture that those are the only ones.

A quantum analysis of the interaction of two propagating, quasimonochromatic fields with three-level Λ-type atoms is presented. It is shown that the recently predicted effect of pulse matching [S. Harris, Phys. Rev. Lett. 70, 552 (1993)]–the generation of fields with matched Fourier components–is due to the nonadiabatic response of the medium. This effect leads to a correlation of the high-frequency phase fluctuations of the fields, and may therefore be used to reduce the noise in short-time measurements of phase differences.

We have demonstrated a novel beam splitter for atoms. The J=1 to J=0 system in metastable helium has two independent ‘‘dark’’ states which are radiatively stable. By preparing atoms in the two ‘‘dark’’ states of the $2^3$${\mathit{S}}_1$ level and passing them through a sequence of partially overlapping laser beams tuned to the $2^3$${\mathit{S}}_{1\mathrm{-}}$$2^2$${\mathit{P}}_0$ transition, we cause the atoms in one ‘‘dark’’ state to be deflected by integral multiples of 2ħk, while the atoms in the other ‘‘dark’’ state are undeflected. The excited $2^3$${\mathit{P}}_0$ state is not populated, so the process is unaffected by spontaneous emission. We have observed up to 90% coherent momentum transfer with 4ħk deflection. We conclude by describing how one might construct an atom interferometer based on these ‘‘dark state’’ beam splitters.

We have observed transfer of momentum and ground state population in laser-cooled cesium by adiabatic following of a slowly evolving light field. In this new technique for mechanical manipulation of atoms, spontaneous emission is suppressed since the atoms evolve in a ‘‘dark’’ state that follows the light field. This means that the phase coherence of the atom is preserved so that this technique is useful in the realization of coherent atomic beam splitters and mirrors. Our experimental results are in good agreement with optical Bloch equation calculations.

The nonlocality responsible for violations of Bell’s inequalities is not equivalent to that used in teleportation, although they probably are two aspects of the same physical property. There are mixed states which do not violate any Bell type inequality, but still can be used for teleportation.

The self-dual Einstein equation (SDE) is shown to be equivalent to the two dimensional chiral model, with gauge group chosen as the group of area preserving diffeomorphisms of a two dimensional surface. The approach given here leads to an analog of the Plebanski equations for general self-dual metrics, and to a natural Hamiltonian formulation of the SDE, namely that of the chiral model.

If the neutrino has a finite mass and a magnetic moment it can produce transition radiations when crossing the interface between two media. The transition radiation due to the neutrino magnetic moment can be enhanced by a large Lorentz factor (γ=${\mathit{E}}_{\nu }$/${\mathit{m}}_{\nu }$) for a small value of ${\mathit{m}}_{\nu }$. A new application of the transition radiation to measure the neutrino magnetic moment is discussed.

We have measured the branching ratio for the hyperon radiative decay ${\mathrm{\Xi }}^{\mathrm{-}}$→${\mathrm{\Sigma }}^{\mathrm{-}}$γ from a sample of 211±33 events obtained in the polarized 375 GeV/c charged hyperon beam at Fermilab. We find B(${\mathrm{\Xi }}^{\mathrm{-}}$→${\mathrm{\Sigma }}^{\mathrm{-}}$γ/${\mathrm{\Xi }}^{\mathrm{-}}$→${\mathrm{\Lambda }}^0$${\mathrm{\pi }}^{\mathrm{-}}$)=(1.22±0.23±0.06)×${10}^{\mathrm{-}4}$ where the quoted errors are statistical and systematic, respectively. We have also obtained an indication that the sign of the asymmetry parameter of this decay is positive.

A leading charm meson is one with longitudinal momentum fraction, ${\mathit{x}}_{\mathit{F}}$>0, whose light quark (or antiquark) is of the same type as one of the quarks in the beam particles. We report on the production asymmetry, A=[σ(leading-σ(nonleading)]/[σ(leading)+σ(nonleading)] as a function of ${\mathit{x}}_{\mathit{F}}$. The data consist of 1500 fully reconstructed ${\mathit{D}}^{\pm }$ and ${\mathit{D}}^{\mathrm{*}\pm }$ decays in Fermilab experiment E 769. We find a significant asymmetry for the production of charm quarks is not expected in perturbative quantum chromodynamics.

Peculiar cosmic ray events (Centauros) with anomalously large fluctuations in their isosopin composition have been observed during the past twenty years. Multiparticle symmetrization has been put forward as an explanation of the effect. In this Letter we show how the formation of pions through the sigma channel when combined with symmetrization can lead to a scenario where the isospin distribution is not only broadened but inverted. For reasonable choices of parameters we find that events can actually prefer consisting of either nearly all neutral or all charged pions.

The problem of cluster formation and growth in the first-order quark-hadron phase transition in heavy-ion collisions is considered. Behaving as Brownian particles, the clusters carry out random walks and can encounter one another, leading to coalescence and breakup. A simulation of the process in a cellular automaton suggests the possibility of a scaling distribution in the cluster sizes. The experimental determination of the cluster-size distribution is urged as a means to find a clear signature of the phase transition.

Nuclear level lifetimes have been measured in two superdeformed bands in ${}_{}{}^{194}{}_{}{}^{}\mathrm{Hg}$ using the Doppler-shift attenuation method. Average transition quadrupole moments derived from the lifetimes of an excited and yrast superdeformed bands are ${\mathit{Q}}_{\mathit{t}}$=17.6(30) and 17.2(20)eb, respectively. The Doppler shifts of the excited band relative to the yrast band indicate a slight difference in quadrupole moments [+4(5)%], assuming similar side feeding..ul2 These results imply that the second well is stable and rigid with respect to the particle excitation responsible for this excited band.

We report the measurement of the scalar ${\mathrm{\alpha }}_0$ and tensor ${\mathrm{\alpha }}_2$ polarizabilities of uranium using a light-force technique, the first accurate measurement of the polarizabilities of a refractory element. At the fundamental wavelength of a Nd:YAG laser (1.064 μm) we measure ${\mathrm{\alpha }}_0$=24.9±1.5 A${\mathrm{̊}}^3$ and ${\mathrm{\alpha }}_2$=0.7±1.7 A${\mathrm{̊}}^3$. From these values we determine the dc polarizabilities to be ${\mathrm{\alpha }}_0$=20.3±1.4 A${\mathrm{̊}}^3$ and ${\mathrm{\alpha }}_2$=0.7±1.8 A${\mathrm{̊}}^3$. Calculations of ${\mathrm{\alpha }}_0$(dc) are within 30% of this measurement.